CPB

Corporate Partnership
Board

The International Transport ForumThe International Transport Forum is an intergovernmental organisation with 57 member countries.
It acts as a think tank for transport policy and organises the Annual Summit of transport ministers. ITF is
the only global body that covers all transport modes. The ITF is politically autonomous andadministratively integrated with the OECD.
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understanding of the role of transport in economic growth, environmental sustainability and social
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The ITF organises global dialogue for better transport. We act as a platform for discussion and prenegotiation of policy issues across all transport modes. We analyse trends, share knowledge and promoteexchange among transport decision-makers and civil society. The ITF’s Annual Summit is the world’s
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Case-Specific Policy Analysis Reports
The ITF’s Case-Specific Policy Analysis series presents topical studies on specific issues carried out
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This is the definitive version, 29 May 2017.

ACKNOWLEDGEMENTS – 3

Acknowledgements
The International Transport Forum is grateful for the assistance of Veronica Garibay Bravo,
consultant, Ulises Hernandez, ICCT and Norbert Ligterink, TNO, for their valuable contributions to thisreport as authors of the chapters on Air Pollution and Mitigation Measures in Mexico City Today andReal World Vehicle Emissions. We are grateful too to all of the experts from Mexico and overseas thatparticipated in the workshop organised in Mexico City in January 2017 to exchange experience in thedevelopment of air pollution mitigation and traffic management policies.

STRATEGIES FOR MITIGATING AIR POLLUTION IN MEXICO CITY — © OECD/ITF 2017

4 – ABBREVIATIONS

Abbreviations
AQG

WHO Air Quality Guidelines

AAQD

EU Ambient Air Quality Directive, Directive 2008/50/EC

AQI

Air Quality Index

BAR 90US Bureau of Automotive Repair vehicle inspection test using 1990 criteria

CAF

Development Bank of Latin America

CAM

Metropolitan Environmental Commission

CAMe

Environmental Commission for the Megalopolis

CIVAR

Mexico City Remote Inspection and Surveillance Center

GDI

Gasoline direct injection

HNC

Hoy No Circula (No-Driving Days)

ICCT

International Council for Clean Transportation

IMECA

Air Quality Index

INECC

National Institute of Ecology and Climate Change

ITF

International Transport Forum at the OECD

LEZ

Low emission zones

NAFIN

Nacional Financiera (development bank)

PCAA

Environmental Atmospheric Contingency Program

PICCA

Comprehensive Program against Atmospheric Pollution

PIREC

Comprehensive Program of Pollutant Emissions Reduction

PM

Particulate matter

PROFEPAFederal Attorney's Office for Environmental Protection

PROAIRE

Air Quality Improvement Programs

PVVO

Mandatory Vehicle Inspection Program

OBD

On-board diagnostic system

SCR

Selective catalytic reduction

SEDEMA

Ministry of Environment of Mexico City

SEMARNAT

Ministry for the Environment and Natural Resources

SIMAT

Atmospheric Monitoring System for Mexico City

SIVER

Mexico City Vehicular Inspection Information System

WHO

World Health Organization

ZMVM

Metropolitan Area of Valle de MéxicoSTRATEGIES FOR MITIGATING AIR POLLUTION IN MEXICO CITY — © OECD/ITF 2017

TABLE OF CONTENTS – 5

Table of contents
Abbreviations ................................................................................................................................................. 4
Executive summary ....................................................................................................................................... 7
1. Air pollution mitigation strategies ......................................................................................................... 13
Air pollution mitigation priorities in Mexico City ..................................................................................... 13
Controlling emissions in Mexico’s real-world urban driving conditions .................................................. 19
Fuel quality ................................................................................................................................................ 21
Incentives for early adoption of cleaner vehicles....................................................................................... 22
Inspection and maintenance ....................................................................................................................... 23
Restrictions on the use of vehicles ............................................................................................................. 25
General traffic management ....................................................................................................................... 36
Enhancing and promoting sustainable transport alternatives ..................................................................... 39
Communication strategies.......................................................................................................................... 43
Recommendations ...................................................................................................................................... 45
2. Air pollution and mitigation measures in Mexico City today.............................................................. 59
Introduction: The current situation and the high ozone concentration episodes of 2016 .......................... 59
Measures to control vehicle emissions ...................................................................................................... 69
Low emission zones ................................................................................................................................... 81
Outline of other policies considered for development of a new strategy to reduce air pollution .............. 85
3. Real-world vehicle emissions .................................................................................................................. 87
The current state of affairs in Europe ........................................................................................................ 87
Robust emission control technologies ....................................................................................................... 87
The type approval test as the standard for compliance .............................................................................. 88
The two separate worlds of type-approval and on-road in-use testing for light-duty diesel vehicles........ 88
Designed, or optimised, for the type-approval test .................................................................................... 89
Normal conditions of use as part of type-approval .................................................................................... 90
Impacts of driving conditions on emissions............................................................................................... 90
Emission measurement and modelling ...................................................................................................... 91
Impacts of malfunctioning and tampering ................................................................................................. 91
Impact of real-world emission performance on the effectiveness of local air quality policies.................. 92
Conclusions................................................................................................................................................ 93
Annex 1. ..................................................................................................................................................... 94
References .................................................................................................................................................... 97
List of participants .................................................................................................................................... 102
Notes ........................................................................................................................................................... 107

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EXECUTIVE SUMMARY – 7

Executive summary
Background
Air quality has improved substantially in Mexico City since the 1980’s but the city experiences
regular episodes of ozone and particulate matter concentrations in the air that exceed health limits. The
geography of the conurbation, situated in a bowl surrounded by mountains, frequently traps air over thecity allowing pollutants to accumulate. Updating of pollution alert limits in 2012 and 2014 to reflect
international health standards revealed the full extent of the problem. In the first half of 2016 theMetropolitan Zone of the Valle de Mexico (ZMVM) experienced 115 days of ozone concentrations
above the acute exposure health limit, with 16 days exceeding pollution alert levels. This led to theimplementation of temporary restrictions on the use of vehicles, extended through to July. The ozone
alerts and particulate concentrations in the air that frequently approach health limits underline the needfor updating and adding to existing emissions control and traffic management policies.
The air pollution exposure health limits that apply in Mexico City are in line with World HealthOrganization (WHO) guidelines and similar to those adopted elsewhere in North America and in Europe.
Regular breaching of the limits is not confined to Mexico. There are 43 designated Non-Attainment
Areas for ozone in the USA under National Ambient Air Quality Standards, classified as extreme in theLos Angeles South Coast Air Basin and the San Joaquin Valley. An increasing number of European
cities record air pollution in excess of EU standards and many large cities in Asia experience severe
pollution episodes. Policy frameworks have been developed in the USA and Europe to require cities inregular breach of standards to take special measures to cut emissions, with recourse ultimately tofinancial penalties if improvements are insufficient.
Against this background of common problems, the International Transport Forum (ITF) at theOrganisation for Economic Co-operation and Development (OECD) and the Development Bank for
Latin America (CAF) together with the Ministry of Environment of Mexico City (SEDEMA) convened aworkshop for regulators and policy makers in Mexico City and the surrounding Metropolitan Zone in
January 2017 to discuss air pollution mitigation strategies with their peers in other major cities and withexperts on vehicle emission control technologies. The objective was to provide insights into the mosteffective short- and long-term options on the basis of international experience. This report presents thefindings of the workshop together with the reports prepared for it on air pollution and mitigation
strategies in Mexico City and recent findings of research into emissions from vehicles in real-world
driving conditions.

Findings
Mexico City and adjacent municipalities in the Metropolitan Zone of the Valle de Mexico havedeveloped stringent air pollution mitigation measures with a fairly comprehensive set of measures similar
to policies developed in some cities in other OECD countries. Pollution is generated by a wide range ofindustrial and other activities. Emissions of volatile organic compounds from non-mobile sources remaina key factor in the formation of ozone in the Valle de Mexico but as in all large cities, substantial
reductions in emissions from road vehicles are a key strategy for achieving clean air.

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8 – EXECUTIVE SUMMARY

The factors that drive excess emissions from vehicles in the real-world traffic conditions of the city
are critical to determining priorities among the potential measures available to mitigate air pollution. In
Mexico City, traffic is dense and frequently heavily congested. Average speeds are low and stop-go
conditions standard. Emission control technologies must be effective in these conditions if they are to beof relevance to improving the air of the city. Diesel emission control technologies in particular have had
a poor record in cutting emissions in these circumstances. The latest generation of standards for heavy
duty vehicles (US EPA 2010 and Euro VI standards for heavy duty vehicles) and the monitoring andcontrol systems they require represent a major advance. Early results of testing on the road suggest that
unlike previous control systems they perform as well in the real world as in laboratory testing for typeapproval.
Traffic management measures to achieve more fluid conditions, including by restricting the numberof vehicles on the road, are the other main approach to mitigating emissions. In the short term, reducing
speeds on motorways and trunk roads in the metropolis is the single most effective measure for cutting
air pollution available to State governments. Emissions rise steeply at higher speeds and enforcing amaximum 80 km/h limit cuts emissions significantly. Lower limits also tend to make traffic more fluid
and increase the overall capacity of the road and variable speed limits are employed in many cities tomanage congestion. Introducing efficient parking prices is central to reducing traffic flows andencouraging modal shift towards public and non-motorised modes.
Restrictions on the use of vehicles are a key part of the emergency response to pollution alerts in the
Metropolitan Zone of the Valle de Mexico. These are based on Mexico City’s strict vehicle inspection
and maintenance programme, which relies on best-practice techniques of exhaust emissions testing,including checks of the on-board diagnostics system, similar to the approach used in California.
Restrictions on vehicle use depend on the certified emissions class of each vehicle after inspection. The
system is also employed to restrict the use of more polluting vehicles on a routine basis one day a week
and on Saturdays. Exemptions from restrictions provide a strong incentive for the purchase of cleaner
vehicles. Vehicle ownership taxes should similarly be differentiated by emissions class.
Providing good quality public transport services as an alternative to the use of private cars and taxis
is an essential complement to measures that restrict or charge for the use of private vehicles. The
programmes developed for coordination, reform and investment in public transport across the ZMVM
need to be pursued as a matter of urgency.
A range of measures should be taken to cut emissions and improve air quality the ZMVM and an
integrated approach is advisable. The following recommended actions cover the main areas forintervention; a more disaggregated and complete list of recommendations is developed at the end ofChapter 1, identifying the responsible authorities in each area.

Recommendations
Consolidate the use of on-board diagnostic system checks in the mandatory vehicle inspection andmaintenance programme
On-board diagnostic (OBD) system checks are an important tool in the emissions testing procedure underthe mandatory vehicle test, inspection and maintenance programme in Mexico City together with tailpipe
exhaust gas testing. Both tests are required because of the greater effectiveness of OBD interrogation in
detecting deficiencies, diagnosing faults and avoiding fraud, whilst dynamic tailpipe exhaust testing willcatch problems invisible to OBD checks, ensure that emissions are within the current limits and also

STRATEGIES FOR MITIGATING AIR POLLUTION IN MEXICO CITY — © OECD/ITF 2017

EXECUTIVE SUMMARY – 9

provides the default test for those vehicles that do not comply with current OBD requirements or are notequipped with OBD (of course only vehicles equipped with OBD should be eligible for certification in
the cleanest vehicle categories).
The Ministry of Environment of Mexico City has submitted evidence on the importance of bothtests to achieving the environmental objectives of the law on inspection and maintenance to defend thetest procedure in court, where it has been challenged on constitutional grounds. As recent court rulings
undermine the test and inspection system, further evidence including the present report should be madeavailable to the judiciary. At the same time, the Federal Ministry of Environment (SEMARNAT) shouldtake legal action against car manufacturers and distributors that fail to ensure vehicles are equipped with
an operational OBD system, which has been required by law for new vehicles since 2006.
Improve the mandatory vehicle inspection programme to include mechanical roadworthinesschecks and to measure ultrafine particulate emissions
The condition of tyres, clutches, brakes and other mechanical components is important for bothemissions controls and safety. The particles emitted by wear processes are toxic and may account for asmuch as half of all PM10 emissions from vehicle use. Including mechanical checks in mandatory vehicle
inspections will create a maintenance culture that will improve air quality. It is also important to control
ultrafine particulate emissions. Measurement of particle numbers should be included in tailpipe exhaustgas testing in anticipation of future vehicle emissions regulations and to monitor the impact of gasoline
direct injection technologies on the severity of particulate matter pollution.
Adopt state-of-the-art emissions standards for heavy duty diesel vehicles without delay
Mexico City already incentivises the use of the latest generation of trucks and buses by exempting
them from the restrictions on use introduced to manage air pollution. The standards should be adopted
nationally for all new vehicles without delay. The Federal Environment Ministry has proposed adopting
EPA 2010 / Euro VI emissions standards for heavy duty vehicles for introduction in 2019. A decision has
been delayed while the potential value of transitioning through Euro V standards is assessed. Given thevery small reductions in emissions achieved in practice on the road by Euro V standards in Europe andthe very large improvement achieved with Euro VI standards, the deliberations should conclude rapidlythat a transition through Euro V standards would be counterproductive and Euro VI standards should be
agreed on without further delay for implementation as early as possible.
Verify vehicle emissions in real world driving conditions
As the recent research on emissions from light and heavy duty vehicles in real world driving
conditions summarized in this reports make clear, emissions in typical urban conditions can exceed
levels proscribed in type approval standards many-fold. High altitude also has a strong non-linear
influence on emission and some advanced engine and emissions control technologies might be moresensitive than older models. It is important to understand the impact on mitigation measures. Verificationof emissions from vehicles meeting US EPA and Euro standards at altitudes typical of Mexico City
should be undertaken by Mexico City, the Mexican Petroleum Institute or other pertinent institution as amatter of priority. In principle the in-use conformity regulations adopted in the latest Euro emissions
standards are the approach to addressing anomalies related to altitude but this should be confirmed withexperimental evidence.

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10 – EXECUTIVE SUMMARY

Continuously update the system of restrictions on vehicle use in the Metropolitan Zone of the Vallede Mexico and improve enforcement
Further differentiation of restrictions should be introduced to incentivise purchase of cleaner light
duty vehicles. The latest light duty vehicle emissions standards (EPA Tier 3 / Euro 6) should be used as
reference values ahead of their incorporation in national standards so that at an appropriate point in the
future the highest environmental class certification is awarded only to these vehicles. Reciprocalarrangements for enforcement and collection of fines for contravening restrictions should be agreed
between the States participating in the Environmental Commission for the Megalopolis (CAMe) as
whereas vehicles in contravention of the rules can be fined by any of the jurisdictions collection of thefine is not automatically pursued across borders.
Phase in a city-wide low emissions zone
The current Hoy no circula system of regular restrictions on the use of more polluting vehicles
could be complemented, and perhaps replaced in the long term, by a city-wide low emissions zone, using
the existing vehicle inspection, classification and identification system. In principle a low emission zone
would have a bigger potential for reducing emissions as the incentives for using cleaner vehicles andswitching to other modes of transport would apply every day. Preparations for introduction of a low
emission zone are recommended, with studies to examine practical implementation issues. The initial
focus would be control of heavy and light duty freight vehicles. Should a generalised low emission zone
be introduced, the current system of additional restrictions during pollution alerts (PCAA) would need tobe remain in place.
Differentiate the tax on vehicle ownership to provide incentives for cleaner cars
The annual tenencia tax on vehicle ownership should be differentiated on the basis of the emissions
characteristics of the vehicle rather than its value. This would provide incentives to purchase cleaner
vehicles in every segment of the market. The six States that cooperate in the CAMe should end
exemptions to the tax (qualified as subsidies in Mexico) and consider earmarking revenues to investment
in public transport. This should improve acceptance of this tax as well as generating a revenue stream tosupport alternatives to the use of the car.
Introduce incentives for ultra-low sulphur diesel and gasoline at national level
Regardless of technology, improving fuels reduces emissions from every vehicle on the road andincentives to use ultra-low sulphur diesel and gasoline, both of which are available in the metropolis, area way to achieve to cut emissions from all vehicles. International experience suggests that tax
differentiation to ensure that the price at the pump of ultra-low sulphur fuels is competitive would
produce a shift to 90% clean fuels in the space of one or two years.
Reduce speeds on motorways and ring roads
Speed limits produce immediate reductions in emissions at very little cost. The 80 km/h speed limit
on urban motorways and ring roads introduced in Mexico City in 2015 should be adopted across theMetropolitan Zone of the Valle de Mexico and enforced to ensure vehicles operate more often in the 50
to 90 km/h range in which emissions control technologies work best. Limiting speeds to below 80 km/h
also helps maintain free flow traffic for longer as congestion builds.

STRATEGIES FOR MITIGATING AIR POLLUTION IN MEXICO CITY — © OECD/ITF 2017

EXECUTIVE SUMMARY – 11Manage parking more effectively and consider road pricing
Extending the Ecoparq programme of charges for on-street parking throughout the Metropolitan
Zone of the Valle de Mexico is an important step to establishing an effective strategy for managing
traffic. Moving from fixed to differentiated parking rates will be necessary to better reflect the value of
public space in different areas (according to demand and land-use) and incentivise modal shift in areasthat are well served by public transport and have good facilities for cycling. Parking space regulations
should set an objective of reducing supply where density and land-use mix is high and public transport,
walking and cycling facilities are available. Abolishing minimum requirements for off-street parking inbuilding codes is in line with actions taken by other world cities that seek to move away from caroriented development and achieve more transit-oriented development patterns. Specific mechanisms to
reduce congestion are also needed. The more widespread use of on-road parking charges is an effective
tool for this together with road pricing and congestion charges and their potential for practicalimplementation should be evaluated.
Improve sustainable transport alternatives to cars and taxis
Provision of good quality public transport services is essential to the success and acceptability ofrestrictions on the use of vehicles. Measures to improve strategic planning and coordination of public
transport services as set out in the PROAIRE programme should be pursued as a matter of high priority.
This includes reform of bus concessions throughout the Metropolitan Zone of the Valle de Mexico andwhere agreements are made to scrap microbuses and operate routes under consolidated concessions withhigher standard vehicles, ensure the old vehicles are actually scrapped and do not continue to be used incompetition with the new services. Investments in metro and BRT systems have proved effective. The
programme of investments underway in improved metro and BRT station access and protected walking
and cycling infrastructure is an important part of the package and should continue.
Consolidate initiatives to integrate land-use and transport planning
For the long term more integrated land-use and transport planning is essential to containing air
pollution. Planning tools to assess the impact of development on traffic and fund necessaryenhancements to public transport have been introduced in Mexico City but these now need to be linked
explicitly to planning consents. The property development mobility impact assessment procedureprovided for under Mexico City’s 2015 Mobility Law needs to be implemented fully and linked directly
to the process of awarding construction authorisations. This planning framework for ensuring developers
contribute to investment in public transport should be extended across the Metropolitan Zone of the Vallede Mexico and other options for diversifying funding for investment in public transport explored. A
Mobility Master Plan for the Zone, linking funding allocation to priorities established jointly by the Stateand Federal authorities should be established. The CAMe appears to be the most effective regional
institution available to establish such a plan.
Improve retrofit programmes with inspection, maintenance and quality certification
Pilot programmes to retrofit buses in Mexico City with diesel particulate filters are reported to be
successful and have been extended. An inspection and maintenance regime should be introduced toensure that filter efficiency is preserved in use and any clogging problems are addressed properly and not
simply by removing filters. The programme of subsidies to replace3-way catalytic converters on carsfailing inspection and maintenance tests should be backed by a quality and durability certification system
for the replacement parts.

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12 – EXECUTIVE SUMMARY

Introduce emissions regulations for off-road vehicles and mobile machinery
Construction machinery for buildings, roads and so on is currently unregulated. These are asignificant source of emissions. Emissions controls for new vehicles and machinery along the lines of EU
regulation 2016/1628 should be introduced. The development of restrictions on use of this machineryshould be considered for pollution alerts.
Invest more in communicating with the public on the development of new anti-pollution measures
Ensuring support for air pollution mitigation measures, and particularly those that restrict the use ofvehicles, begins with information campaigns to raise awareness of the health risks of contaminated air
and the steps that individuals and government can take to reduce exposure to pollution. Proposals for
new measures should be subject to public consultation. Data on the effectiveness of measures taken
should be disseminated on a regular basis through public reports.

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1. AIR POLLUTION MITIGATION STRATEGIES – 13

1. Air pollution mitigation strategies
Air pollution mitigation priorities in Mexico City
Pollution is generated by a wide range of industrial and agricultural activities. The pollutants ofmost concern vary by location and concentrations in the air are sometimes determined more at regionalor hemispheric level than locally. But in all large cities, substantial reductions in emissions from roadvehicles are seen as a key strategy for achieving clean air.
The health effects of excess concentrations of particulate matter (PM), nitrogen dioxide (NO2) andozone (O3) are outlined in Box 1.3. PM and O3 concentrations are the main concern in the Metropolitan
Area of Valle de México (ZMVM).1 Whilst O3 is less toxic than some particulates, excess concentrations
irritate the respiratory tract and greatly exacerbate the inflammation provoked by particulate pollution
and allergens in the air. NO2 has similar effects to ozone.
In Mexico City, the central part of the metropolitan area, it is estimated that if the WHO
recommendations on air quality were observed more than 1 400 deaths per year could be avoided. These
deaths cost around MXN 30 billion (Mexican pesos) to society (INECC, 2016b).
Mexico has set national ambient air quality standards for O3, NO2, sulphur dioxide, carbon
monoxide and particulate matter (PM10 and PM2.5). These are similar to standards in the US and Europe(Tables 1.1 and 1.2). Legislators in the EU have basically adopted the WHO guidelines, with a degree oftolerance permitted in some cases for the time being (EEA, 2016). In cities where the levels are exceeded
more often than the tolerated number of days, national governments are required to take remedial action.
This follows the approach originally adopted in the US where areas that do not attain National Ambient
Air Quality Standards ultimately face withholding of federal funds.
The Metropolitan Area of Valle de México has defined an air quality index (AQI) to characterise air
pollution. This follows the methodology developed first in the US. Mexican and US air quality bands andpollution thresholds for O3 and PM10 are summarised in Table 1.3. One hundred points on the AQI
corresponds to national health limits for acute exposure.
In the ZMVM, 150 points on the AQI is the threshold for issuing emergency pollution health alerts.
Since April 2016, this is the level for alert phase 1 and corresponds, for O3, to an hourly average
concentration of 155 ppb and for PM10 to a 24 hour moving average of 215 µg/m3. These legal limits are
regularly exceeded and action therefore must be taken to reduce emissions. In the European Union,
attention has focussed on ozone (hourly average alert threshold 240 µg/m3), NO2, sulphur dioxide and
PM. For PM, the EU regards no level of exposure as safe. The O3 alert threshold in the ZMVM
(equivalent to 310 µg/m3) is 29% higher than the EU limit and the PM10 threshold over four times higher
than the defacto EU limit (Table 1.2). In the USA alert thresholds vary from city to city.

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14 – 1. AIR POLLUTION MITIGATION STRATEGIESBox 1.1. Air pollution chemistry
Mobile sources contribute 79% of NOX, 21% of PM10, 20% of VOC and 96% of CO emissions in the
ZMVM. These pollutants have health impacts and contribute to the formation of O3. The chemistry of air
pollution is complex and concentrations in the atmosphere are often interdependent. NO and NO2 (known
collectively as NOX) are produced through oxidation of nitrogen in the air by combustion at high temperature(including in internal combustion engines). NO and NO2 react with chemicals in the air to form secondary
particulates. They also react with volatile organic compounds (VOC) under the action of sunlight to form ozone.
The rate of ozone formation can be limited by NO X or by VOC concentrations. In the ZMVM the controlling
factor is VOCs. At night, in the absence of sunlight, NO breaks down ozone into oxygen and NO 2. .

Table 1.1a. Selected Mexican National Ambient Air Quality Standards

Ozone
PM10
PM2.5

Period8 hours
1 hour
24 hours
Yearly24 hours
YearlyLevel
70 ppb95 ppb75 µg/m3
40 µg/m3
45 µg/m3
12 µg/m3

Statistical form of the limit
Annual maximum moving average for 8 hours
Hourly mean
Daily mean
Annual mean
Daily mean
Annual mean

Sources: Informe Calidad del Aire 2015; http://www.aire.cdmx.gob.mx/default.php?opc=%27ZaBhnmI=&dc=%27Yw==;
http://www.aire.cdmx.gob.mx/descargas/publicaciones/flippingbook/informe_anual_calidad_aire_2015v3/mobile/#p=12,.

Table 1.1b. Selected US National Ambient Air Quality Standards

Ozone
PM10
PM2.5

Period8 hours
24 hours
24 hours

Level
70 ppb150 µg/m3
35 µg/m3

Statistical form of the limit
Annual 4th highest daily maximum over 3 years
Not to be exceeded more than once a year over 3 years
98th percentile averaged over 3 years

Sources: US EPA https://www.epa.gov/criteria-air-pollutants/naaqs-table

Table 1.2. European Air Quality Standards and WHO Air Quality Guidelines (AQG) (µg/m3)

O3
NO2
PM10
PM2.5

WHO
AQG
100
50 ppb
40
200
20
50
10
25

EU
Standard
120
60 ppb
40
200
40
50
25
-

Averagingperiod8 hour daily max
Annual mean
1 hour mean
Annual mean
Daily mean
Annual mean
Daily mean

Days exceedance allowedWHOEU
25 average over 3 years

3

EU Air Quality Alert
Threshold240 (1 hour average)
120 ppb

1835

400
50, WHO AQG used defacto

3

Sources: WHO 2006; EU AAQD 2008/50/EC; EU Directive 2002/3/EC relating to ozone in ambient air.

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1. AIR POLLUTION MITIGATION STRATEGIES – 15

Table 1.3. Air Quality Index (AQI) Breakpoints in Mexico and the US
AQI
0–
50
51 –
100
101 –
150
151 –
200
201 –
300
301 –
400
401 –
500

Air quality category
MX
Buena

US
Good

RegularModerateMala

Muy Mala

Unhealthy
Sensitive
GroupsUnhealthy

Extremadamente
Mala

Very
Unhealthy
Hazardous

O3(ppb 8-hour)
MX US
0
54
55
70
71
85
86
105
106
200

O3
(ppb 1-hour)
MX
US
0
70
71
95
96
125
154
164

PM10
(µg/m3 24-hour)
MX
US
0
0
40
54
41
55
75
154
76
155
214
254

PM2.5
(µg/m3 24-hour)
MX
US
0
0
12
12
12.1
12.1
45
35.4
45.1
35.5
97.4
55.4

155
204
205
404
405
504
505
604

215
354
355
424
425
504
505
604

97.5
150.4
150.5
250.4
250.5
350.4
350.5
500.4

165
204
205
404
405
504
505
604

255
354
355
424
425
504
505
604

55.5
150.4
150.5
250.4
250.5
350.4
350.5
500.4

Sources: SEDEMA; US Electronic Code of Federal Regulations, Part 58, Ambient Air Quality Surveillance.

Box 1.2. UK Pollution Alerts
Air pollution Alerts are issued when any of the following thresholds in EU Directive 2008/50/EC are exceeded:
Ozone Information Notice
180 µg/m3 for 1 hour
Ozone Alert
240 µg/m3 for 1 hour
Sulphur Dioxide Alert Nitrogen Dioxide Alert 500 µg/m3 for 3 consecutive hours over 100km2 area
400 µg/m3 for 3 consecutive hours over 100km2 area
Source: UK Department for Environment, Food and Rural Affairs, https://uk-air.defra.gov.uk/latest/alerts

The likely development of emissions and air quality in Mexico has been modelled by the Institutefor International Council for Clean Transportation (ICCT). Scenarios with and without updating of fuelquality standards and emissions regulations for new light and heavy-duty vehicles to current US
standards were prepared. The results are summarized in the following tables and figures and show thatwithout updating of the standards, emissions of particulate matter and VOCs will grow strongly. NO X
emissions will fall at first as new vehicles meeting the current regulations enter the fleet but this effect isthen outstripped by growth in the population and the number of vehicles on the road. The strong increasein particulate emissions in the baseline scenario reflects the importance of sulphur in fuel in producing
particulates.

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16 – 1. AIR POLLUTION MITIGATION STRATEGIESBox 1.3. Health effects of high air pollutant concentrationsPM

The size of particles is directly linked to their potential for causing health problems. Small particles lessthan 10 micrometres in diameter pose the greatest problems, because they can get deep into the lungs
and some get into the bloodstream. Exposure to such particles can affect both lungs and heart. Particle
pollution exposure is linked to a variety of problems, including: Premature death in people with heart or lung disease.
 Nonfatal heart attacks.
 Irregular heartbeat.
 Aggravated asthma.
 Decreased lung function.
 Increased respiratory symptoms; irritation of the airways, coughing or difficulty breathing.
People with heart or lung diseases, children, and older adults are the most likely to be affected byparticle pollution exposure.

Ultrafineparticles

Particulates from vehicle exhaust are a known health risk, which decrease life expectancy and quality oflife, although the toxicity mechanisms of the particulate cocktail are still under investigation. The mostdamaging emissions of all are ultrafine particulates (smaller than 100 nanometres), with metals andother toxic substances attached to their surfaces. These are much smaller even than PM2.5, and must be
measured by number of particles not by mass as they weigh so little. The carbon particles produced by
combustion are in themselves relatively harmless but the toxic chemicals they carry into the cells cause
inflammation and damage to cells, resulting in a range of diseases including heart and respiratory
diseases and cancers. Gasoline direct injection engines can produce as many ultrafine particles as diesel
engines.

NO2

Breathing air with a high concentration of NO2 can irritate airways in the respiratory system. Exposure
over short periods can aggravate respiratory diseases, particularly asthma, leading to respiratory
symptoms (such as coughing, wheezing or difficulty breathing), hospital admissions and visits toemergency rooms. Longer exposures to elevated concentrations of NO 2 may contribute to thedevelopment of asthma and potentially increase susceptibility to respiratory infections. People withasthma, as well as children and the elderly are generally at greater risk for the health effects of NO2.

O3

Ozone can cause the muscles in the airways to constrict (as the body responds to exposure by trying toprevent absorption into the blood), trapping air in the alveoli. This leads to wheezing and shortness ofbreath and reduced levels of oxygen in the blood. Ozone can:
 Make it more difficult to breathe deeply and vigorously.
 Cause shortness of breath, and pain when taking a deep breath.
 Cause coughing and sore or scratchy throat.
 Inflame and damage the airways.
 Aggravate lung diseases such as asthma, emphysema, and chronic bronchitis.
 Increase the frequency of asthma attacks.
 Make the lungs more susceptible to infection.
 Cause chronic obstructive pulmonary disease.
These effects have been found in healthy people, but can be more serious in people with lung diseases
such as asthma. Long-term exposure to ozone is linked to aggravation of asthma, and is likely to be oneof many causes of asthma development. Long-term exposures to higher concentrations of ozone may
also be linked to permanent lung damage, such as abnormal lung development in children.

Source: US EPA, https://www.epa.gov/no2-pollution/basic-information-about-no2#Effects (except for ultrafine particules).

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1. AIR POLLUTION MITIGATION STRATEGIES – 17

Figure 1.1. Scenarios for emissions from light and heavy-duty vehicles (tonnes)

Mexico Annual Onroad Exhaust PM2.5 Emissions
200 000
Base Case
150 000
All Standards (sulfur, LD, HD)
100 000
50 000
0
2005

2015

2025

2035

2045

2055

Mexico Annual On-road NOx Emissions
1 800 000

Base Case
Base w/ Nationwide I&M
HD US 2010 and 15 ppm diesel
LD Tier 2 and 30 ppm gasoline
LD Tier 3 and 10 ppm gasoline
Nationwide I&M for Tier 2/3

1 600 000
1 400 000
1 200 000
1 000 000
800 000
600 000
400 000
200 000
0
1995

2015

2035

2055

Mexico Annual On-road VOC Emissions
900 000

Base Case
Base w/ Nationwide I&M
LD Tier 2 and 30 ppm gasoline
LD Tier 3 and 10 ppm gasoline
Nationwide I&M for Tier 2/3

800 000
700 000
600 000
500 000
400 000
300 000
200 000
100 000
0
2005

2015

2025

2035

2045

Source: ICCT, workshop presentation by Kate Blumberg.

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18 – 1. AIR POLLUTION MITIGATION STRATEGIES

Table 1.4. Fuel quality and vehicle emission standards scenarios for Mexico
Regulation

Fuels/Vehicles

Base scenario (2016 standards)

Control scenario

Fuel standards

Gasoline

Metro areas: 30 ppm
Rest: 85% 300 ppm;
15% 30 ppm
Metro areas: 15 ppm
Rest: 500 ppm

2016
2017-20192020+
2016-20172018-20192020+
2018-20202021-2024
2025+
EPA 2010

DieselVehicleemissionstandards

PM: US Tier 1
NOx: US Tier 2 bin 7
Phase-in complete after 2013
EPA 2004

Light-duty

Heavy-duty

150 ppm
30 ppm10 ppm
500 ppm
15 ppm10 ppmTier 2Tier 3 phase-in
Tier 3

Source: ICCT, workshop presentation by Kate Blumberg, 2017.

Figure 1.2. Contribution of standards to emissions reductions in 2035
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%

52%
86%

93%

100%

48%

NOx

14%

7%

CO

VOC

PM2.5

LD and gasoline sulfur standards

0%
-10%
-20%
-30%
-40%
-50%
-60%
-70%
-80%
-90%
-100%

CO

NOx

VOC

SO2

PM25

BC

-11%
-18%
-27%
-44%

-29%

-31%
-43%
-53%
-66%

-84%
-96%

-91%

% change with control scenario (transport)

HD and diesel sulfur standards

Source: ICCT, workshop presentation by Kate Blumberg..

Table 1.5. Difference in air quality between scenario with updated standards and baseline, 2035
Air quality indicator (population-weighted)

Nationwide

Mexico City

Annual mean PM2.5
8-hour maximum ozone
1-hour maximum ozone (annual mean)
1-hour maximum ozone (spring mean)-17.6%-8.1%-9.5%-11.8%-19.5%-4.9%-6.3%-13.7%

Source: ICCT, workshop presentation by Kate Blumberg.

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1. AIR POLLUTION MITIGATION STRATEGIES – 19

Controlling emissions in Mexico’s real-world urban driving conditions
The factors that drive excess emissions from vehicles in the real-world traffic conditions of the city
are critical to determining priorities among the potential measures to mitigate air pollution. Recent
research has greatly improved the understanding both of emissions in the real world and the damage
done to health (see: Chapter 3; ECMT, 2006).
In Mexico City traffic is dense and frequently heavily congested with low average speeds andstop-go conditions. Emissions control technologies must be effective in these conditions if they are toeffectively cut emissions in the city.
New vehicles sold in Mexico comply with either US or EU emission standards, both are valid andmanufacturers can chose which equivalent standard to follow. For cars and heavy trucks both regimes areused in practice but most buses are manufactured in compliance with the European standards.
Heavy-duty vehicle emissions standards adapted to congested roads
Until the most recent generation of heavy vehicles, compliant with Euro VI / EPA 2010 2 standards,
nitrogen oxide (NOX) emission control systems performed poorly in urban conditions. In particular, thetest regime in the EU, which focused on a very narrow range of engine performance, drove adoption oftechnology that fails to remove NOX until engines reach temperatures much higher than typical in urban
traffic. In addition, the standards for heavy vehicles in both Europe and the US focus on conditions ofrelatively high engine loads and speed. Powerful modern truck engines almost never reach these loads incity traffic. In consequence the engines developed respect emissions limits under open highway driving
conditions, where the latest trucks produce less pollution than most diesel cars,3 but performed poorly
outside of these conditions until effective in-service compliance rules were incorporated. In Europe, thiswas with the 2013, Euro VI generation of standards. These standards also adopted a particulate number
limit for the first time, important in providing the necessary incentive to control ultrafine particulate
emissions.
Until off-cycle on-road testing was incorporated, successive emissions standards saw little or no
improvement in cutting NOx emissions in urban driving conditions. The first results of real-world testingof Euro VI vehicles are promising, although more research will be required to establish conclusively that
this generation of vehicle performs reliably under prolonged urban-only use. Specialised vehicles such as
garbage trucks will require particular attention due to their atypical drive cycles. Depollution systems canalso be tampered with in use to increase power or to avoid the need for refills with NO X-control reagent(urea solution marketed as AdBlue). Regular inspection is required to ensure this does not happen.
US regulations imposed stronger on-board diagnostic (OBD) requirements than under Euro V
standards so suffered much less of a NOX control performance gap, but even under the new emissions
control test regimes, both the EU and US truck emissions control technologies work most effectively at
prolonged constant speeds of 50 to 90 km/h, i.e. open highway driving. Clearly it is not possible toensure trucks can always drive at these speeds in urban environments. Additionally, apart from on urban
freeways, speeds must be limited to 50 km/h or less for road safety imperatives.
Early adoption of Euro VI standards for buses and trucks
Current federal emissions standards in Mexico for new trucks and buses specify Euro IV
regulations. Promoting Euro V vehicles would achieve little gain. The standards and procedures adopted
for Euro VI, on the other hand, have achieved a ten-fold improvement, largely because of the adoption of
new in-service compliance requirements. Mexico City has rightly adopted these standards under its
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voluntary inspection and maintenance (I&M) scheme, which exempts trucks from restrictions on
circulation when pollution alert countermeasures apply. The proposed adoption of Euro VI standards
under federal regulations for new vehicles in 2020 should be agreed without further delay and ideallybrought forward. A potential two-year transition phase with Euro V standards, currently underconsideration, would clearly be counter-productive; ICCT estimates that it would result in one million
tonnes excess NOX emissions a year. The voluntary I&M scheme for heavy vehicles clearly demonstrates
that there is no obstacle to using Euro VI trucks in the Mexican market today.
Ultrafine particles from gasoline engines
Unlike diesel emissions controls (for both heavy and light-duty vehicles), the three-way catalytic
converters used to control emissions on gasoline cars have shown very good correlation between test andreal world performance, with successive improvements in control with each generation of emission
standard. However, emissions of particulates were only measured in terms of mass not number until thelatest, 2015 Euro 6 light-duty vehicle standards (EUR-LEX, 2012).4 The change was in response to the
spread of gasoline direct injection (GDI) engines, which if not appropriately controlled emit ultrafine
particulates, albeit on a much smaller scale than poorly maintained vehicles that burn lubricating oil. GDI
cars are spreading rapidly in Latin America, including in Mexico, and controlling them with a particle
number limit is important.
Evaporation of gasoline
In relation to emissions of volatile organic compounds (VOCs), the US EPA 2010 Tier 3 light-duty
vehicle regulations have stricter, more effective controls than European standards for controlling fugitivehydrocarbon emissions – evaporative losses from the engine, petrol tank and during refuelling. The seals
and vapour traps used to achieve the limits are not advanced technology and do not add significant costto vehicles. Controlling these emissions is particularly important in Mexico as high temperatures and thehigh altitude mean such losses are large when uncontrolled and are an important source of ozone
precursor emissions. Moreover VOCs appear to be the limiting factor in the formation of ozone in theValle de Mexico.
Cutting VOC and ultrafine particulate emissions in the ZMVM
Ideally Mexico should adopt a combination of the latest European and US light-duty emissions
standards to address emissions of both ultrafine particles and volatile organic compounds. Following theusual approach and allowing manufacturers to meet either standard to replace the current
Euro 4 standards as quickly as possible is indicated. In the immediate term Mexico City could introduce
incentives in its inspection and maintenance and No-driving day (HNC) systems to promote a shift toTier 3 compliant vehicles, to contribute to reducing excess ozone pollution episodes.
Controlling off-road vehicle emissions and the use of advanced filters
Controlling emissions from off-road vehicles is an important part of air quality improvement incities and should become part of mitigation strategies in Mexico. These emissions are regulated undernational emissions standards in Europe and the US.5 Non-road mobile machinery emissions have been
regulated in the European Union since 1997. The latest regulations (2016/1628) apply from 1 January
2017 and should be the reference for development of a standard in Mexico.

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1. AIR POLLUTION MITIGATION STRATEGIES – 21

Retrofit and local proving of emission control technologies
Mexico City has run a pilot diesel particulate filter (DPF) retrofit programme for buses since 2015.
This follows successful real world testing of retrofits in 2005 by SEDEMA with CTS-Embarq Mexico,
US EPA and US AID, that found them to be effective in reducing particle numbers as well as the mass ofparticulate emissions. Given the challenges of urban driving conditions for filter regeneration, continued
monitoring will be essential to the credibility of the program as it is expanded. Severe problems with
DPF retrofit programs have been encountered elsewhere, for example in the Netherlands, where filters
have suffered rapid clogging, sometimes resulting in fires. A specific maintenance and inspection regime
is needed for large scale retrofit programs.
For selective catalytic reduction (SCR) NOX treatment systems on heavy-duty vehicles, in-use
testing will also strengthen the credibility of any incentives to introduce vehicles that use this technology(Euro V and Euro VI trucks and buses). As noted, early testing of Euro VI trucks in urban conditions
shows a ten-fold improvement over previous vehicles but testing on a broad range of vehicles including
buses and garbage trucks is indicated given the disappointing results of SCR technology on older
vehicles in urban conditions. At the workshop, transport for London emphasised the importance of theresearch and testing in local conditions that it commissions to support development of London’s low
emissions zones and bus replacement schemes as important to the effectiveness and public acceptance ofthe measures taken. TfL developed its own test cycle to match conditions in London traffic and its
verification program was important to the success of SCRT retrofits on London buses.
Ensuring the quality of retrofitted pollution control equipment is essential. Even some of thethree-way catalytic converters available on the after-market are poor quality and perform badly andshould not be used in retrofit programs. Certification and inspection of approved systems for retrofit isimportant together with monitoring of accredited installers of aftermarket emissions control systems.
Certification needs to include durability regulations with a five-year/50 000 miles (80 000 km) warranty.
For particle filters certification should ideally cover the efficiency in terms of reducing particle numbers
as well as the mass of emissions.

Fuel quality
Ultra low sulphur gasoline and diesel
Reducing the sulphur content of gasoline and diesel would have immediate benefits for air quality in
the ZMVM. Reducing sulphur in gasoline to 10 ppm would improve the performance of the catalytic
converters on every car on the road. Ultra low sulphur diesel at 15 ppm is ideal for the latest particulate
filters and NOX control systems. This fuel is available in Mexico City, although not everywhere in the
country, and there are diesel particulate filter systems that work effectively at much higher sulphur levels(only systems using precious metal coatings are sensitive to sulphur).
The availability of low sulphur fuel in Mexico City is not an obstacle to incentivising the latest
emissions control technologies but promotion of low sulphur fuel, for example through differentiatedtaxation, would have significant immediate benefit. Clamping down on illegal sales of non-standard fuels
through unregistered distribution channels would also have pollution benefits and protect vehicle owners
from damage to their engines.
Alternative fuels and drivetrains
Electric vehicles produce no tailpipe emissions and are a potentially valuable part of emissions
mitigation strategies. The cost of unsubsidised vehicles makes electric passenger cars a marginal part of
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the market in Mexico to date. The city has plans for an electric highway on one of its southern arterial
roads, with investment in electric buses. There are also several existing electric trolley bus routes – a
relatively low-cost alternative that might be expanded. Transport for London now requires all new
double-decker buses to be hybrid diesel-electric and all single deck buses to be electric. It plans toconvert all taxis to plug-in petrol-electric hybrid engines. Mexico City began a pilot project to support
the introduction of electric taxis in 2012 which continues to expand.
Natural gas conversions have been used successfully in cities including Delhi to cut emissions ofparticulates from buses, microbuses and motorised rickshaws as engine-out emissions are very low. They
have made a particularly useful contribution to mitigation and sustainability strategies in Gothenburg in
Sweden where buses run on methane recovered from digesting solid waste from water treatment plants.
There are some issues associated with natural gas vehicles. Leakage in the transport and fuelling of
natural gas adds to VOC and greenhouse gas emissions. CNG motors have lower torque than diesel orgasoline engines and the storage of gas on the roof of buses changes the handling characteristics of thevehicles. NOX emissions can be high if poorly controlled. CNG vehicles could be part of mitigation
strategies in Mexico if high standards of pipeline transport and refuelling are met.
Liquefied petroleum gas (LPG) presents similar characteristics to natural gas in combustion.
However, LPG distribution is restricted under current ozone alert response measures in the ZMVM andencouraging its use for vehicles might therefore be problematic. Its main advantage is cost, with market
prices usually somewhat below gasoline or diesel.
Policies to promote the use of electricity for transport in the city at reasonable cost, i.e. trolley buses
and the metro and small scale market development pilots, are the most pertinent of the options foralternative fuels and drivetrains.

Incentives for early adoption of cleaner vehicles
In anticipating future federal standards to promote cleaner vehicles at the local level, Mexico City isfollowing good practice elsewhere. European Union emissions regulations allow member states to use
tax incentives (differentiated registration and road use taxes) to accelerate introduction of vehicles
meeting new standards ahead of the regulatory deadlines. A number of countries have made use of thisfacility. In all of the European countries where electronic road pricing has been introduced for heavy
vehicles rates have been differentiated according to the Euro emissions class of the vehicle. Germany
used road pricing discounts in 2005 to stimulate early development of the market for Euro V trucks.
Greater use could be made of this approach in Mexico, for example with incorporation of Euro VI
standards in the eco-zones under development in a number of cities in the CAMe region In addition,
vehicle categories “00”and “0”, assigned according to the I&M system, could also be differentiated,
reserving the “00”category for Tier 3/Euro 6 light-duty vehicles (see next section).
Most European countries have differentiated vehicle taxation on environmental grounds following
an EU policy paper on taxation that promoted differentiation on the basis of CO 2 emissions (EU, 2005).
Taxes on registration and ownership of vehicles and annual circulation taxes have been differentiated on
the basis of emissions in 20 member states (ACEA, 2016), replacing flat rate charges and charges taxes
based on the value of cars (some use a combination of factors). This has had a powerful effect on themarket for new cars. Taxation is most strongly differentiated in France, Denmark and the Netherlands
and the average fuel economy for new cars is lowest in these countries. Differentiation of vehicle taxes inrelation to air pollutant emissions would have a similar market steering effect.

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1. AIR POLLUTION MITIGATION STRATEGIES – 23

In Mexico, the tenencia is a vehicle ownership tax, devolved to the Federal States since 2012. Some
States have abolished the tax but those that retain it set rates in relation to the value of the car with
exemption in some cases below a minimum threshold. The three States of the ZMVM levy the tax but set
different thresholds, USD 18 000 in Mexico City, USD 26 300 in the State of Mexico and USD 41 350 inHidalgo (OECD, 2015). In the CAMe region Tlaxcala has a threshold of USD 26 300, Puebla andMorelos no longer levy the tax. These differences lead many households in Mexico City to registervehicles in other States. Restructuring the tax in the States levying it to provide incentives for Tier 3 /Euro 6 vehicles, with a taper rather than a cut-off threshold to differentiate according to value, would
provide a valuable stimulus to the market for clean vehicles. Weaker incentives might be included forTier 2 / Euro 4 cars.

Inspection and maintenanceA stringent emissions control inspection and maintenance (I&M) system has been developed for theZMVM, requiring inspection twice a year. In 2014, with support from the Environmental Commission
for the Megalopolis (CAMe), the six States of the megalopolis agreed to harmonise all I&M programmeswith the system in the ZMVM. Harmonising the programmes has long been an objective because inaddition to the benefits to the population in each of these states of bringing all inspection procedures andemission standards up to the level of the ZMVM, a large number of vehicles from the area travel throughthe ZMVM in a daily basis. Moreover there was a strong incentive to register vehicles outside Mexico
City in States with less stringent I&M procedures.
In June 2016, the National Ministry of Environment (SEMARNAT) issued an emergency standard(NOM – EM-167-SEMARNAT-2016) that applies in all CAMe States. This emergency standard will be
replaced by a permanent standard in July 2017. The new standard established OBD checks as part of themandatory vehicle emissions testing and inspection programme. It also revised the limits for tailpipe
testing and introduced testing with remote sensing devices to identify high-emitters on the street.
Inspection based on interrogation of the cars’ OBD system allows rapid processing and, in many cases,
identification of the likely cause of any excess emissions. It also records the functioning of emissions
control systems in use over time and guards against interference with engine controls to change theperformance characteristics of the vehicle specially to pass the emissions test. OBD testing detects fourand a half times as many defects as a standard tailpipe emissions test according to data from California’s
I&M system. However, until all vehicles in Mexico have a homologated and certified OBD system,
reliance on only OBD testing for determining compliance on emission levels is not possible. Based on
Mexico City´s experience since July 2016, some vehicles with high measured tail-pipe emissions would
have passed inspection if only OBD checks had been required. Therefore OBD checks combined with
tailpipe exhaust emission tests should be used for vehicle certification in Mexico City and this systemshould be extended throughout the CAMe States as planned. Measures to thwart OBD systemmanipulation should be considered to prevent illegal falsification of results.
In response to recent challenges in court to the legality of using OBD checks in addition to tailpipe
sampling, the CAMe authorities should prepare a report on the importance of OBD to achieving theenvironmental objectives of the law on the obligatory vehicle maintenance system. This should be
prepared to standards sufficient for judges in the constitutional courts to accept the necessity of OBD
testing.
The requirement for I&M centres to use OBD checks has delayed the process of harmonising theinspection system across the CAMe States (in the meantime vehicles registered in States where thetechnology is not available can go through voluntary I&M in Mexico City and State of Mexico).

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Nonetheless, completing the transition along with the introduction of the more stringent emission
standards specified by the new regulation will reduce pollution.
Notwithstanding this improvement, the omission of motorcycles from the system is an important
flaw that needs to be addressed. While these vehicles still constitute a small share of the fleet, their
numbers are rapidly increasing and a significant share have two-stroke engines and thus emit high levelsof emissions. Affordable electric motorcycles are rapidly replacing conventional motorcycles in Chinese
cities and could be incentivised under the I&M system.
Fraud and enforcement have been a persistent problem in I&M systems wordwide. Although
Mexico City has implemented its own Centralized Vehicular Inspection Information System (SIVEV)
and established a Remote Inspection and Surveillance Center (CIVAR), enforcement remains achallenge. To eliminate fraud, the system could introduce some of the procedures used in California.
Tests are carried out in licenced concessions throughout the State but the data from the tests istransmitted electronically via the internet to a central analytical station in Sacramento City which issues
the test result. This effectively guards against many kinds of fraud in the local garages that run the tests.
Licenced concessions are also subject to periodic audit and undercover operations to inspect unmarked
control vehicles are mounted as an additional check to prevent fraud.
In California, OBD testing is backed by cross-checks that strip down engines that pass tailpipe
emissions tests and fail OBD tests, and vice-versa, to understand the causes of failure. A team of around30 people work on ensuring and improving the quality of the regime. In the European Union tailpipe
emissions gas sampling remains the principle test method because of the unfolding emissions defeat
device scandal surrounding diesel cars. Both OBD and tailpipe testing are needed for a reliableinspection considering the range of vehicle ages and the standards/OBD requirements they are certified
to. California is also switching to OBD based testing for heavy-duty vehicles equipped with thesesystems.
In addition to harmonising testing procedures and standards, the I&M system would benefit from ajoint agreement of CAMe States to harmonise enforcement procedures. Significant shares of noncompliant vehicles still exist in the megalopolis zone. For this to change it is important that all States
within the Megalopolis make effective the mandatory character of the I&M programme by imposing asanction in the case of non-compliance (in the States of Morelos, Hidalgo, Puebla and Tlaxcala this is not
the case). In addition, an agreement for all six States of the megalopolis to enforce payment of fines
imposed on vehicles registered in their State regardless of where in the region the vehicle was stopped
and fined, e.g. for breaching Hoy no circula restrictions (see following section), would make a major
contribution to improved emissions control.
A majority of jurisdictions in OECD countries require heavy and light-duty vehicles to undergo
periodic motor vehicle inspections for safety and roadworthiness although in some inspections are
required only on transfer of ownership. In most federal countries, including the US, Canada andAustralia, the type of inspection regime is the responsibility of State jurisdictions. In the US, 17 Statesrequire periodic safety inspection. In Australia all States require roadworthiness testing, either periodic
inspection or testing on transfer of the vehicle. Japan requires cars to undergo safety and roadworthinesstesting after three years and then every two years. In the European Union, Directive 96/96/EC requires all
member states to carry out periodic safety and emission inspections for all motor vehicles and setsminimum standards for inspection of private and commercial vehicles. Private cars and commercial
vehicles up to 3.5 t must be inspected after 4 years at the latest and then every two years. Heavy-duty
vehicles and taxis must be tested annually for safety and roadworthiness. Around half of the EU member

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1. AIR POLLUTION MITIGATION STRATEGIES – 25

states begin testing at three years, with some from two years, and many make testing annual from 10
years onwards.6
Roadworthiness and safety testing have benefits also for the environment as worn mechanical parts
such as brakes or tyres can result in excess particulate matter emissions. It is estimated that exhaust andnon-exhaust traffic-related sources contribute almost equally to total traffic related PM10 emissions (EEA
2016a; JRC 2014). The composition of the emitted particles depends on the materials used in the
manufacture of brake linings, tyres and asphalt. Heavy metals, organic compounds, sulphur,hydrocarbons and other toxic materials are emitted during the wear processes
Box 1.4 Car ownership restrictions in Asia
In China a number of cities restrict vehicle ownership rather than use. Shanghai was the first city to introduce
auctions for the right to own a car, in 1994. The result is that car numbers per head and per dollar of GDP are half
those in Beijing. The value of a car licence plate is currently USD 12 500 in Shanghai. With congestion and air
pollution increasingly serious problems, Beijing introduced its own lottery-based restrictions on car ownership in
2010. Since then six other cities have introduced combinations of auctions and lotteries. Elsewhere in Asia,
Singapore has the most complete system of instruments to manage car ownership and use. It employs a licenceplate auction system that roughly doubles the cost of owning a car. Land-use and public transport policies aretightly integrated and dynamic road charging is used to control access to the centre and fine tune the speed oftraffic on arterial roads (ITF, 2010).

Restrictions on the use of vehicles
An increasing number of cities around the world restrict access for vehicles to the city centre or
restrict access to over a larger area to the cleanest or most recent vehicles. This creates incentives topurchase cleaner vehicles. In some cases these incentives are designed to anticipate national emission
standards.
Like Mexico City, a number of authorities in Europe also use traffic restrictions as pollution control
measures during peak pollution episodes. France introduced windscreen stickers to classify vehicles byemissions characteristics under its new Crit’air system in 2016, using it to limit vehicle circulation
during pollution episodes for the first time on 23 January 2017. The standards apply nationally and themayors of cities with an air pollution problem are able to make use of it as required by local mitigation
programmes. The system is differentiated similarly to Mexico’s Hoy no circula (HNC), although based
simply on the emissions regulations applicable to each vehicle rather than the results of vehicle testing.
The scheme entered force in January 2017, replacing an undifferentiated system of odd-even number
plate driving restrictions on alternate days during pollution episodes.
The vehicle classification system is set out in Table 1.6, largely corresponding to age but
differentiated by the fuel used by the vehicle. Older and dirtier vehicles are prohibited from driving
throughout pollution episodes. The more severe the pollution the more categories of vehicle are
restricted. All electric vehicles are classified green and exempt restriction. All plug-in hybrids andvehicles fuelled with compressed natural gas are rated 1 and exempt restrictions together with Euro 5gasoline light-duty vehicles, Euro VI heavy-duty diesel vehicles and Euro 4 motorcycles. The
countermeasures applied on 23 January 2017 banned the circulation of category 5 vehicles (Euro 2
light-duty diesel vehicles and Euro III heavy-duty vehicles) along with all older, unclassified vehicles.

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Table 1.6. France’s Crit’air vehicle classification system, 2016

Source: Mairie de Paris.

Enhancing Mexico City’s Hoy No Circula (No-driving Day) programme in the short term
The ZMVM’s Hoy No Circula (HNC) vehicle restriction system provides incentives for fleet
modernisation by exempting cleaner vehicles from restrictions and placing the most extensive
restrictions on the most polluting vehicles. This is a significant improvement on most other restriction
systems based on licence plate number, which make no differentiation between vehicle emission
characteristics. Driving restrictions are applied on a regular basis, not just during high pollution episodes.
The regular restrictions apply one day a week (the day depends on the last digit of the number plate) andtwo or all Saturdays, depending on the tested emission characteristics of the vehicle (Table 1.7). During
peak pollution episodes additional vehicle use restrictions are implemented as part of the environmental
alert programme (PCAA). Between April and July 2016, restrictions on vehicle use during alerts wereextended to all light-duty vehicles regardless of emissions class (overriding exemptions for 00 and 0classes). Additional restrictions were also applied during the alert to fuel distribution centres, carburation
centres and freight transport. In the case of the latter, this has meant that driving restrictions based on
number plates, and regardless of vehicle emission classification, are applied to all freight vehicles

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1. AIR POLLUTION MITIGATION STRATEGIES – 27

traveling through the ZMVM. These additional measures were agreed as a result of co-ordination ofby
the States and Federal Governments through the CAMe.
The HNC classifies vehicles according to emissions control equipment and the results of I&M tests.
Vehicles are identified using the windscreen stickers issued by the I&M programme. Electric and hybrid
vehicles obtain a windscreen sticker that entitles them to be exempt from all driving restrictions.
Vehicles classified “00” and “0” are also exempt from regular restrictions. Normally they are also
exempt from restrictions during pollution alerts but the special measures applied by the CAMe from
April to July 2016 extended restrictions to these vehicles.
Table 1.7. No-Driving Day scheme restrictions on vehicle use
Restrictions on vehicle use for certified inspection categories 1 and 2(00 and 0 types exempt)
Windscreen
sticker colour

Last digit on
number plate

Yellow

5&6

Weekdays

Saturdays 05:00-22:00
1

2

Odd plates 1st and 3rd
Saturday of the month
Even plates 2nd and 4th
Saturday of the month

All vehicles
every Saturday

MondayPink

7&8

TuesdayRed

3&4

Wednesday

Green

1&2

Thursday

Blue

9&0

FridayUncertified vehicles
Every day

05:00-11:00

Plus one day a week

05:00-22:00

Every Saturday
05:00-22:00

Source: SEDEMA.

The “00” classification is given to new light-duty vehicles (complying with Euro 4 / EPA Tier2
standards or better) and heavy-duty diesels that comply with Euro VI / EPA 2010 standards.
“0”classification can be attained by light-duty vehicles with a three-way catalytic converter and a second
generation OBD system, meeting emission standards equivalent to Euro 3 / EPA Tier 1 (corresponding to2006 models onwards). Cars of this type can also be given a “1” sticker according to I&M emissions test
results. “0”stickers are awarded to heavy-duty diesels that meet Euro IV / EPA 2004 (2008 models
onwards) and present no faults on OBD testing. Restrictions apply to vehicles classified “1” and “2” asdescribed in Table 1.7. Details of the emissions testing requirements are outlined in Chapter 2; see Table
2.5 for a summary of current requirements for certification of gasoline, diesel, natural gas, hybrid andelectric vehicles.
Programmes that link traffic restrictions to environmental performance need continuous updating as
new technologies become available. New emission limits for the ZMVM were introduced by NOM –EM-167-SEMARNAT-2016 as one of the responses by CAMe to ozone alerts. These were incorporated
in the I&M testing program, notably introducing the OBD test requirement for heavy and light-duty
vehicles to obtain “0” rating, thus resulting in stricter requirements for exemption from traffic
restrictions. Incentives to stimulate development of a market for Euro 6 / Tier 3 light-duty vehicles in the
ZMVM could be introduced through the system ahead of national standards for all new vehicles through

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28 – 1. AIR POLLUTION MITIGATION STRATEGIES

addition of a “000” class or modification of the categories of vehicle eligible for “00” and “0” classes.
Restrictions imposed during pollution peaks could then take advantage of this difference, exempting only
vehicles with the most advanced technologies, and imposing some restrictions on all other vehicles.
Currently motorcycles are not included in the I&M or HNC systems. This should be rectified, withdifferentiation between less and more polluting vehicles, with or without testing. As in the case ofFrance, motorcycles can be classified using the same stickers as for other vehicles.
Enforcement
The effectiveness of measures to restrict the use of vehicles, both on a regular basis as well as
during smog episodes, depends on the extent to which they are respected. The penalties for contravening
the restrictions in Mexico City can be severe (including confiscation of vehicles) and the restrictions are
enforced by the police with fines. One weakness is that fines levied by the police force in Mexico City on
vehicles registered in other States are not pursued if unpaid. An agreement on reciprocal processing offines between the States co-operating in the Regional Environment Commission (CAMe) would be
useful in closing this loophole.
Automatic number plate recognition (ANPR) systems are used to enforce restrictions in many cities
operating low emissions zones, congestion charges and tolls for the use of infrastructure. These could beapplied to the no-driving day and pollution alert restrictions in Mexico City and to future schemes.
ANPR is suited to controlling access to relatively small areas because of the cost of monitoring a large
number of access points on an extensive road network but can also usefully be deployed lesssystematically to monitor some of the main trunk roads used by large numbers of vehicles. ANPR isalready in use in Mexico City to enforce speed limits on sensitive parts of the urban freeway network.
During the discussions at the workshop, Transport for London stressed the importance ofmonitoring the compliance of restrictions on vehicle use and incentives to use cleaner vehicles as one of
the keys to acceptance of such mitigation measures.
Use of revenues
Revenues from charges for I&M services, from fines for contravening restrictions on vehicle use
and from charges to access eco-zones or congestion charging zones can be used to fund flanking
measures. This can enhance acceptance of emissions control policies. In California, for example, an
USD 8 certification fee is levied on top of the charge for I&M testing. This is used in part to fund a
program that assists poor households with up to a USD 500 grant towards repair or up to USD 1 500 for
replacement of vehicles that fail emissions testing. In London around half of the revenues from thecongestion charge to enter the central part of the City are absorbed by the cost of implementing thesystem with ANPR. The remaining revenues are invested in the public transport system, particularly inenhancing the bus network. In Mexico City there is no earmarking of revenues from enforcement of
restrictions on the use of vehicles today, but this might be considered either to fund better enforcement or
to invest in public transport or cleaner vehicles. Some of these revenues could also be directed toreinforcing the technical capacity of the CAMe. Currently, CAMe’s budget is composed of funds
assigned by the Federal Government plus a fund composed of resources allocated by member States(equivalent to MXN 5 (Mexican pesos) for every vehicle controlled by I&M programmes) (OECD,2015). Given that the institution needs to develop expertise on multiple transport and non-transport
related environmental issues, channelling some of the charges levied from car regulation to training andto expanding the staff of CAMe could significantly strengthen the capacity of the institution to provide
the evidence base for decisions taken by the governing body of the institution.7

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1. AIR POLLUTION MITIGATION STRATEGIES – 29

Shifting towards alternative traffic restriction schemes
A range of systems to restrict traffic are used in cities around the world, including low emission
zones (LEZs), congestion charging systems and road pricing schemes, with the primary or secondary aimof improving air quality. The effects of these schemes are instructive as the authorities in the ZMVM andthe larger CAMe region examine ways to increase the effectiveness of the HNC and consider potential
alternative schemes.
Number plate based restriction systems tend to create perverse incentives for households topurchase a second vehicle with a registration number that permits driving on the days the first vehicle isrestricted. A second vehicle in the household generally results in higher mileage driven overall and thesecond vehicle is often an older car with high emissions. Studies of the impacts of the HNC in Mexico
City found evidence that this was the case with the HNC when it was introduced, with reductions incongestion and pollution attained in the period immediately after implementation largely off-set in thelonger-run (Gallego et al., 2013). The HNC programme saw important adjustments in 2008 when
exemptions for cleaner vehicles were introduced, creating incentives to buy new vehicles instead of
second vehicles. Later studies demonstrated that, while there is still evidence of an increase in the vehicle
fleet due to the programme (of about 3%), the programme had an important effect in accelerating fleet
renewal (Centro Mario Molina, 2013). Earlier evaluations show that identifying impacts among different
income groups and between times of the day is of relevance (Gallego et al., 2013). Another common way
of coping with the restrictions has been to use taxis. Because of over-supply, taxi rides are relatively
cheap and there is no shortage of taxis despite being subject to the HNC. Another strategy is to organiserides with other household members or friends. Since such carpooling trips do not necessarily share thesame itinerary, in many cases trip length increases (Davis, 2017).Conducting a detailed study to quantify
each of these effects and their ultimate result in terms of emissions would provide a solid basis for futurereforms of the programme.
Restrictions under LEZs, congestion charging and road pricing schemes are applied uniformly every
day, or every week-day. Thus, the purchase of additional vehicles is not a solution for avoiding
restrictions. More polluting vehicles are subject to control every day and, in some cases, occasional useof dirtier vehicles is permitted against payment for access rather than according to number plate. This
provides stronger incentives to switch to cleaner vehicles or to public transport.
Box 1.5 describes the Integrated Impact Assessment that was carried out by TfL for the Ultra-Low
Emission Zone in London. As was the case in London, such evaluations need to consider socio-economic
impacts, particularly for vulnerable groups, and a strategy for supporting these groups in coping withsuch effects should be developed.
A number of small scale LEZs with differing characteristics are under consideration in city centresin the megalopolis. Co-operation through the CAMe could play an important role in generating
guidelines and expertise for the design of such schemes and alternatives and complementary measures tothe HNC in general. In the case of LEZs guidelines should highlight the need for schemes to be based oncommon emissions standards, have explicit objectives for air quality improvement and provide
incentives for using the cleanest vehicles. Guidelines should also emphasize the need for establishing anadequate perimeter for LEZs. The very small scale of the schemes currently under consideration in the
CAMe area means they will have little impact on air quality.
While detailed evaluations would be needed to determine the size of the benefit of shifting to acity-wide low emission zone in Mexico City, the following sections provide insights into the potential
benefits. These are based on discussions between experts and local authorities during the workshop on

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30 – 1. AIR POLLUTION MITIGATION STRATEGIES

possible ways in which an LEZ could become part of the strategy for improving air quality in the
ZMVM. If an LEZ were to replace the HNC for regular, day to day traffic management, Stage 1 andStage 2 pollution alert restrictions could be retained for severe pollution episodes, as occasional
restrictions provide relatively little incentive to purchase a second vehicle.

Box 1.5. Integrated Impact Assessment for the ultra-low emission zone in London.
As part of the analysis for the implementation of the ultra-low emission zone (ULEZ), Transport for London(TfL) undertook an Integrated Impact Assessment in order to have a general overview of the possible impacts in a
number of areas including environmental, health, equality and economic and business.
Consultations through workshops were conducted with the main stakeholders including government agencies,
local authorities, consultants, and transport and industry associations. The result was the identification of
anticipated effects associated with the ULEZ. Each one of the impacts was classified according to its scale (minor,
moderate or major effect) and duration (short and medium for less than five years, and long term for more than five
years).
The most relevant impacts identified are:a)Environment: ULEZ would result in improvements in the air quality due reduction in NO 2 and CO2
through the use of low and zero emission vehicles and the use of public and non-motorised transport.

b) Population and equality: The most relevant negative impacts are related to vulnerable groups that could
not afford a compliant vehicle and could be affected by the reduction in the number of vehicles or the costthey need to pay to enter the ULEZ; these groups include female night workers, low-income workers,
school children from low-income families, disabled persons who might have difficulties finding analternative mode of accessible transport, taxi drivers who may choose to retire rather than upgrade to acompliant vehicle, and groups that rely on charitable or voluntary services to access London.
c)

Economic: ULEZ would have an impact on the economy by gaining a benefit associated with improved
health outcomes but would result in more costs for SMEs and tourists due to the reduction of
non-compliant utilitarian and tourist vehicles.

Several measures were proposed to mitigate the negative impacts, these include:

Investment in infrastructure for public transport, walking and cycling.



Increasing the coverage and frequency of night bus services and providing metro services during allnight on some lines.

Promotion of grants to obtain a compliant vehicle for taxis, SMEs, and other vulnerable groups.

Communication strategies to provide useful information to affected groups.

Free transport for school children on TfL services (bus, metro, tram).



Improve physical accessibility in public transport.



Subsidised taxi services for people with reduced mobility.

Detailed information can be obtained from Jacobs (2014), “Ultra Low Emission Zone Integrated Impact
Assessment”,
TfL
consultations.
https://consultations.tfl.gov.uk/environment/ultra-low-emissionzone/user_uploads/ulez-iia-report_final.pdf

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1. AIR POLLUTION MITIGATION STRATEGIES – 31

Introducing a low emission zone focused on heavy-duty vehicles
Heavy-duty diesel vehicles contribute a large share of transport sector emissions. Poor performancein urban traffic conditions of the control technologies deployed until the most recent regulations meanemissions have been seriously underestimated. Diesel cars and delivery vans have similarly tended toemit more pollutants than expected. In response an increasing number of cities are implementing low
emission zones (LEZ), providing incentives for accelerating the introduction of and the newest, lesspolluting technologies. While in some cities LEZs also include passenger cars and motorcycles (e.g.
Berlin, Milan) they have often focused on heavy-duty vehicles (HDVs) and delivery vehicles (e.g.
London, Stockholm). In the case of London, the introduction of passenger cars in the LEZ is now
planned. In Paris the first phase of the LEZ focused on HDVs but was recently expanded to include
light-duty vehicles (LDVs) and motorcycles.
In Mexico City, diesel HDVs (including heavy trucks, buses, and freight vehicles of above
3.8 tonnes) are responsible for close to 17%, 24%, and 38% of PM10, PM2.5 and NOX emissions
respectively (SEDEMA 2014) and the figures are likely to be much higher on the basis of real-world
emissions testing. This suggests a strong case for an LEZ that would, at least in a first phase, focus on
reducing emissions from these vehicles. With the I&M programme and windscreen sticker system forclassifying vehicles according to their environmental performance, key tools are already in place foradministering such a scheme. LEZs in Germany, for instance, have been implemented using a similar
colour windscreen identification system and manual enforcement by the police. Nonetheless, as with thecurrent HNC, the use of automatic number plate recognition (ANPR) cameras would make enforcement
more effective. These are already used to enforce speed limits on some of the city’s urban motorways.
The cost of enforcement with ANPR is driven largely by the data management system required to meetthe local legal standards of proof for identification of drivers in infraction (see ITF, 2010).
International experience has shown that to be effective the area covered by a LEZ needs to berelatively large in relation to the total extent of a city (see Chapter 2). London currently has the largest
LEZ, covering most of Greater London. Maintaining the current area of Hoy No Circula scheme for theestablishment of an LEZ (i.e. the whole of the ZMVM) might be a good option. The ZMVM accounts fora significant share of the total vehicle-kilometres travelled by freight vehicles for the whole country sothis could serve a second purpose of incentivising the introduction of new technologies in the national
fleet (particularly in the surrounding States that are part of the CAMe).
Low emission zones can completely ban certain categories of vehicles, which is the case of LEZs in
Stockholm and Paris. Alternatively, these can also impose a charge for entering the designated area forvehicles that do not meet a certain emission standard, as in London. In each case, introducing such ascheme through progressive phases, announced well in advance, has been important. Box 1.5 shows thedifferent phases for implementation of the LEZs in Paris and London. In the case of the Metropolitan
Area of Valle de México, either approach or a combination of the two could be implemented. Whatever
the exact design of the scheme, this should have a clear objective of accelerating introduction of Euro VI
and phasing out HDVs without effective OBD systems and particle filters. Experience in London showsthat in the case in which a charge for entering the area is set, this should be set at a level where thecompliant vehicle becomes the cost effective option, i.e. where frequent users will find paying the charge
every time they need to go in more expensive than changing their vehicle.
A number of programmes have been introduced in Mexico to promote fleet improvement andrenewal for diesel HDVs (the Clean Transport Programme, the Auto regulation Programme, the Vehicle
Substitution Scheme, and the Programme for Modernising the Federal Road Transport Fleet). These

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32 – 1. AIR POLLUTION MITIGATION STRATEGIES

could be linked to an LEZ, which would facilitate introduction of the policy and accelerate vehicle
turnover while reducing the economic impacts for vulnerable groups.
Shifting from the HNC to alternative restrictions for light-duty vehicles
The vehicle fleet in the ZMVM has increased significantly over the last decades (Figure 1.3).
Private cars and SUVs have shown particular growth and today represent over 75% of vehicles in thearea. There has also been a significant increase in the fleet of taxis and motorcycles (Figure 1.4). In
Mexico City, LDVs (including taxis and SUVs) are estimated to be responsible for 12%, 7% and 26% of
PM10, PM2.5 and NOX emissions respectively (SEDEMA, 2014). As in many cities, pollution isexacerbated by high shares of vehicles with limited emission control technologies and, particularly as
motorisation grows and road space becomes scarce, increasing congestion. Passenger cars in the ZMVM
are mostly gasoline fuelled, which in principle is an advantage compared to cities that have high sharesof diesel cars. Many of the larger SUVs are diesels and it is important to note that new gasoline direct
injection engines in jurisdictions like Mexico where they are not subject to regulation to limit particle
numbers produce more ultrafine particles than the latest diesel cars.
Figure 1.3. Registered vehicles in circulation 1986-2014
6 000 000
5 000 000
4 000 000
3 000 000
2 000 000
1 000 000-

Mexico City

State of Mexico

ZMVM

Source: SEDEMA (2017).

This information was provided by the Ministry of Environment in Mexico City and corresponds tothat collected during I&M procedures. The numbers are significantly lower to those reported by theInstitute of Statistics and Geography (INEGI), presumably due largely to the fact that data reported by
INEGI does not take into account deregistration of vehicles. Contrarily this is better reflected in datacollected through the I&M system since only vehicles in circulation are enrolled in the programme. Also,
the number of vehicles shown corresponds to the definition of the ZMVM that includes Mexico City and
18 municipalities of the State of Mexico, rather than the area defined by CONAPO.
Light-duty vehicles (and motorcycles in several cities) have been made subject to restrictions in
LEZs or to pollution charges as a way for accelerating introduction of new technologies and limiting theentrance of the most polluting cars into certain areas. In Berlin the LEZ bans all vehicles (including

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1. AIR POLLUTION MITIGATION STRATEGIES – 33

passenger cars) that do not have a 4 (green sticker) classification. In terms of passenger cars category 4
corresponds to vehicles that comply at least with Euro 1 standards and have a catalytic converter. In
Paris, Pre-Euro 2 cars and all cars registered before 1997 are banned from the LEZ. Starting in July 2017
this will also apply to Pre-Euro 3 diesel cars, as well as those registered before 2001.
Figure 1.4. Registered vehicles by type in ZMVM 1990-2014
5 500 000
5 000 000
4 500 000
4 000 000
3 500 000
3 000 000
2 500 000
2 000 000
1 500 000
1 000 000

1990

1992

1994

1996

1998

2000

2002

2004

2006

2008

2010

2012

-

-

-

-

-

-

-

-

80

221

233

427

551

Motorcycles

27 97831 35232 72542 81761 13165 74972 90093 927

109 444

123 407145 698172 162262 212

Vehicles more 3 tons

37 74549 71454 45254 20256 55481 30088 36894 365145 580

147 778

162 991

168 176

173 822Buses

21 60320 207

23 67223 97423 05725 07731 70434 74047 85944 30447 00950 73447 136

Trucks44 62156 34049 66753 33351 01738 76842 50047 61853 27554 98569 78274 30579 187

Vehicles less 3 tons

41 71547 41250 57352 33357 45863 64873 11476 20920 92224 17527 02143 59746 967

Pick Up146 623156 162

157 551

151 342159 058

161 812171 271

140 769304 122347 082398 276402 546

400 329

Microbuses

16 41831 07733 10733 24932 72233 06233 44836 39434 04032 75331 62535 17524 113Van

29 356

19 64321 09421 117

5 594

7 942

24 36523 21945 14245 16545 80173 58452 165

Taxis

66 15067 87169 74592 222

96 639109 792

112 452

113 510178 342179 535

200 769

247 562210 168

Cars and SUV

1 656 644 1 847 334 1 995 991 1 984 434 2 211 798 2 435 720 2 809 007 3 188 555 3 172 965 3 550 708 3 831 425 3 744 482 3 962 903

BRT

2014

Source: SEDEMA (2017).

Implementing policies that target congestion and road-use explicitly
In the case of Milan, a first scheme involving driving restrictions was implemented in 2008 as apollution charge called ECOPASS. The central ring road of the city was the area chosen as the perimeter
where the pollution charge would be levied. Free entrance was granted to the cleanest vehicles (class I:
hybrid, electric, LPG, and CNG vehicles; and class II: gasoline car Euro 3 and 4, diesel car Euro 4 withadvanced particulate filters, gasoline light-duty freight Euro 2, 3 and 4; and diesel light freight Euro 4
with advanced particulate filters). Entrance to all other vehicles was granted only on payment of acharge, which increased according to the level of emissions. The measure had significant effects inaccelerating the transition to better technologies. In the initial stages traffic levels were also reduced. A
significant modal shift towards public transport in the area (on average 23 000 additional passengers on
the underground metro line) was one of the reasons behind this. The reduction in congestion was in turnbeneficial to surface public transport, which saw an increase in its commercial speed (about 13% for the
tramway and 20% for bus and trolleybus).

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34 – 1. AIR POLLUTION MITIGATION STRATEGIESBox 1.6. Phases for implementing LEZs in London and Paris
London
The London low emission zone (LEZ) is an area that covers most of Greater London (1 572 square miles). It
operates 24 hours per day, every day of the year, and is controlled with cameras that read number plate; this tells
automatically whether the vehicle meets the LEZ emissions standards, is exempt, is registered for a discount, or if it
must pay the daily charge.
Date

Type of vehicle

2008

Heavy vehicles
Heavy Vehicles

2012

Delivery Vans

Vehicles that must pay a charge to enter
Euro III or lower for PM10 and vehicles registered as new before 2000.
The daily charge is GBP 200.
Euro IV or lower and vehicles registered as new before 2005
Euro 3 or lower for PM10 and vehicles registered as new before 2001. The
daily charge is GBP 100.

An ultra-low emission zone (ULEZ) was announced in 2015 and will be implemented by 2020 in Inner London.
This will restrict the circulation of all vehicles.
Cars and smalldelivery vans
Large delivery vansand minibuses
Heavy vehicles
Motorcycles

Petrol, Euro 4 or lower + registered as new before 2006 or daily charge of GBP 12.50.
Diesel, Euro 6 and registered as new before 2015 or daily charge of GBP 12.50.
Petrol, Euro 4 or lower + registered as new before 2007 or daily charge of GBP 12.50.
Diesel, Euro 6 and registered as new before 2016 or daily charge of GBP 12.50.
Euro VI or lower and registered as new before 2014 or daily charge of GBP 100.
Euro 3 or lower and registered as new before 2006 or daily charge of GBP 12.50.

In June 2016, the Mayor of London announced new air quality measures including the intention to levy an emissions
surcharge (known as the “T charge”) on older vehicles entering or driving in Central London through an addition to
the existing Congestion Charge and to bring forward implementation of the ULEZ to 2019 and expand it. The
proposal is to expand the ULEZ zone to all of Greater London for heavy vehicles and extend it for all vehicles fromthe small central zone to the North and South Circular Roads. A public consultation was held in the last quarter of2016 (TfL, 2016).
Paris
The LEZ introduced by the Mairie de Paris in September 2015 covers the City of Paris, the central part of themetropolis, covering an area of 105 km2.
Date

Type of vehicle

September 2015

Heavy vehicles
Private vehicles andlight-duty vehicles

July 2016

Motorcycles
Heavy vehicles

July 2017

Private vehicles andlight-duty vehicles
Heavy vehicles

Vehicles that are banned
Pre-Euro III and vehicles that entered circulation before 1
October 2001. All days from 8:00 to 20:00.
Pre-Euro 2 and vehicles that entered circulation before 1
January 1997. From 8:00 to 20:00 on working days.
Euro 1 and motorcycles that entered circulation before 1
June 1999. From 8:00 to 20:00 on working days.
Pre-Euro III and vehicles that entered circulation before 1
October 2001. Every day from 8:00 to 20:00.
Pre-Euro 3 diesel and vehicles that entered circulation
before 2001. From 8:00 to 20:00 on working days.
Pre-Euro 4 and heavy vehicles that entered circulation
before October 2006. Every day from 8:00 to 20:00.

By 2020, the goal is to restrict the use of all diesel vehicles and to tighten restrictions on gasoline vehicles:
Motorcycles
Cars
Light-duty vehicles
Trucks and buses

Euro 3 or lower and vehicles that entered circulation before 2007.
Euro 4 or lower and that entered circulation before 2011.
Euro 4 or lower and LDV that entered circulation before 2011.
Euro V or lower and vehicles that entered circulation before 2014.

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1. AIR POLLUTION MITIGATION STRATEGIES – 35

Nonetheless, not levying a charge on road usage but rather on pollution meant that as a higher shareof vehicles became compliant with standards, gaining free entrance, traffic reductions declined. In theinterests of targeting congestion specifically, the authorities made the transition from the ECOPASS
system to the “Area C” scheme in 2012. The new scheme is a combination of a LEZ, banning entrance tothe inner ring for the most polluting vehicles, and a congestion charge, levied on all other vehicles when
they enter the zone.
In the case of London, traffic restrictions have been introduced both to incentivise cleaner
technologies and to reduce congestion. The LEZ was established with the first objective making freightvehicles cleaner. An ultra-low emission zone (ULEZ), setting much tighter standards for free entrance
into the central area of the city and covering all vehicle types is planned to be implemented by 2020 (seeBox 1.5). London also implemented a congestion charge in 2003 for both light and heavy vehicles. The
scheme has a flat rate to be paid when entering or traveling within an inner city zone and is enforced
through closed circuit TV and automatic number plate recognition. The introduction of an emission
surcharge as a supplement to the congestion charge has been proposed as a transition stage in introducing
the ULEZ.
The congestion charge in London had significant effects in reducing congestion during its first
decade of implementation. Modal shifts from private to public and active modes of transport were asignificant part of this result. However, since 2012 vehicle speeds on major roads in Central London
have been falling and journey time reliability within the area has worsened (Transport Committee, 2017).
There are multiple reasons behind this. There has been a significant reallocation of road space inaccordance to more sustainable and inclusive mobility goals, i.e. prioritising pedestrian, cyclists andpublic transport users. This has off-set to a certain degree the decrease in private car use. Going back on
those policies would not be desirable. Transport for London has identified a number of actions with thepotential to reduce congestion further. For example, better managing delivery services (e.g. with delivery
consolidation centres and “click and collect” deliveries by supermarkets at Tube and rail stations in thesuburbs, where commuters can pick up goods on their journey home) to control the rapid increase of vandelivery traffic; and better regulating private-hire vehicles (which are rapidly growing in number and are
not subject to the congestion charge).
A report by the London Assembly proposes that in order to increase its effectiveness, the congestion
charge scheme should be modified, introducing differential charge rates, becoming closer to a roadpricing scheme. With the current flat rate, the system fails to price road usage according to theavailability of road space during the day or to distance driven. Thus it also falls short in incentivisingshifts in road usage towards higher capacity times and better matching demand and capacity during theday (Transport Committee, 2017).
Mexico City and the wider ZMVM will need to develop further policies to reduce congestion andpromote modal shift in their pollution reduction strategies as well as maintaining incentives for fleet
renewal. Policies that do not explicitly price road space usage are not a solution to congestion in thelonger run, and the HNC programme, or an alternative LEZ, is no exception. Like London, Mexico Cityis changing road space allocation towards use by pedestrians, bicycles and public transport. The
reduction in road space dedicated to car use will need to be accounted for in evaluating effectiveness ofschemes to restrict car use.
There are a number of ways in which elements of the vehicle restriction schemes in London, Milan,
Paris and Germany could be used in Mexico City and the ZMVM. Alternatives could include creation ofa wide-area LEZ for heavy-duty vehicles, incorporating light-duty vehicles into later phases while

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36 – 1. AIR POLLUTION MITIGATION STRATEGIES

retaining the HNC system for responding to peak pollution episodes. Road pricing might be introducedon highly congested corridors and/or areas where traffic diversion can be contained.
Any scheme should be based on analysis of sufficient detail to identify what types of vehicle traffic
are most relevant to generating congestion and pollution and the levels of charges needed to incentivise
fleet renewal and modal shift, where alternatives to car use are available. Improving and updating data
and analysis will be necessary. Both the latest study on traffic activities and the origin-destination travel
survey realised at metropolitan level are more than 10 years old. Ex-post evaluation is also relevant for
modifying schemes and implementing complementary policies as conditions change.

General traffic management
Parking
The current PROAIRE program in the ZMVM puts an appropriate emphasis on managing traffic toreduce congestion and stop-go driving conditions and improve the flow of vehicles on the city’s roads,
including through intersection alignments, managing traffic lights and preventing unauthorised roadsideparking. Containing the number of vehicles on the road to levels that can be accommodated by thephysical capacity of the system is fundamental. Especially for big cities, parking policies are the starting
point and a powerful tool. Charging for the consumption of valuable road space for parking is essential.
Evidence across the world demonstrates that efficient parking prices can significantly reduce traffic
flows, reducing cruising and encouraging modal shift towards public and non-motorised modes. In someUS cities, 30% of the cars in congested traffic have been found to be cruising in the search for parking
spaces (Shoup, 2007). Parking pricing can help achieve the optimal level of unoccupied parking spaces(15%) required to minimise the amount of cruising time in urban areas (Shoup, 2005; Kodransky andHermann, 2011). In addition, adjusting supply of both on-street and off-street parking according to
supply of public transport services and availability of walking and cycling facilities can help cities inattaining modal shift from private vehicles to these modes of transport.
Mexico City and the ZMVM need to develop an effective strategy for managing parking. As a firststep the Ecoparq programme, which has introduced parking meters in western central areas of Mexico
City, should be expanded to cover all of the city and the ZMVM. An important improvement to current
parking pricing (both for on-street and garage parking) is moving from fixed to differentiated rates that
could better reflect the value of public space in different areas (according to demand and land-use) andincentivise modal shift in areas that are well served by public transport and have good facilities for using
active modes. An important obstacle to doing this in the ZMVM is that maximum on-street parking fees
are set in State fiscal codes. Regulations are needed to give city administrations flexibility to establish
variable parking prices.
Cities like Lisbon, for example, have established parking rates for different areas of the citydepending on demand. The charge is higher in zones with high demand and higher provision of public
transport. In San Francisco, authorities have taken advantage of mobile communications technologies tointroduce smart parking meters with real-time fare adjustments in several of the busiest commercial
neighbourhoods in the city. Evaluation of the SF Park project show significant success. For instance,
target occupancy rate (60-80%) was met 31% more often; incidence of blocks with no available parking
were reduced 16%; and the average time spent searching for parking decreased 43% (5 minutes). In
addition vehicle travel and greenhouse gas emissions from cruising while searching for parking isestimated to have decreased 30%. It is important to highlight that average meter rates dropped (by 4% foron-street meter rates and by 12% for garage rates) as peak rates were introduced. Removing legal

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restrictions to allow flexibility in tariffs for on-street parking will be crucial for authorities in the ZMVM
for setting efficient pricing policies.
Parking space regulations should set an objective of reducing supply where density and land-use
mix is high and public transport, walking and cycling facilities are available. With this objective, cities
like Zurich and Hamburg have implemented parking caps in business districts that have good access topublic transport (OECD, 2015).
International experience also suggests that minimum requirements for parking space in buildings
should be abandoned. Eliminating minimum parking requirements is increasingly common in
metropolitan areas that seek to move away from car-oriented development and achieve moretransit-oriented development patterns. Examples include Denver, Nashville and Sao Paulo. New York,
Portland and Oregon have in addition established maximum parking spaces for property developments incentral areas. In Paris and Ottawa, regulations are also linked to the availability of public transport. The
London Plan (the spatial plan that guides development in London), uses an index measuring public
transport accessibility (PTAL) for calculating recommended parking capacity in new developments
under the principle that higher PTAL level areas provide less parking spaces, in line with the overall goalof encouraging modal shift towards public transport (TfL, 2015).
Speed limits
Fortuitously, speed limits were lowered across Mexico City’s roads in 2015 under improved roadsafety policy. Speeds on urban freeways were reduced to 80 km/h, trunk roads are restricted to 50 km/h
and feeder roads 30 km/h with a 20 km/h limit on sensitive streets, for example near schools. These are
the limits internationally recognised as appropriate to these roads on the basis of damage andsurvivability in collisions and the typical mix of users on these types of roads. These speeds are also
close to optimal for maximising the flow of vehicles on congested roads. On a crowded highway,
vehicles interfere with each other particularly when changing lanes. The result is a need for longer gaps
between vehicles and frequent braking to avoid collision, both of which reduce flow. Monitoring traffic
in these conditions shows that lowering speeds cuts stop-go conditions, increases flow and reduces
average journey times. Reduced speeds are used routinely to manage congestion and increase flow onurban freeways in a number of cities, for example on London’s M25 ring road where speeds are reduced
from 70 to 50 mph. They are also used to cut pollution during smog episodes, for example in Paris on its
Périphérique ring road and on its radial motorways where limits are reduced 20 km/h below the usuallevel. Speed limits are an effective short-term measure for cutting emissions, to the extent they are
enforced and respected; they smooth traffic, moderate the cycle of braking and acceleration, reduce hard
accelerations and cut excess speeds – all factors associated with excess emissions.
The impact on air pollution of speed restrictions has been modelled and monitored in a number ofcities. Goncalves et al. (2008) model the effects of the introduction of an 80 km/h speed limit on trunk
roads in Barcelona. This found small improvements in NO2, SO2, PM10, PM2.5 and CO emissions for theregion as a whole and a marginal impact on O3 concentrations in the air. The small overall change inemissions was thought to be due to congestion keeping speeds down even before introducing the limit
and the relatively small part of the air catchment area over which the limits apply. Close to the main
roads, improvements were significant: 5.7% for NO2, 5.3% for SO2 and 3.0% for PM10 for 24-hour
average concentrations. The reduction in NOX emissions resulted in a local increase in O3 concentrations
as, like Mexico City, in Barcelona O3 formation is limited by VOC concentrations (and NOX breaks
down ozone on balance in the absence of sunshine); nevertheless downstream in the pollution plume O 3
concentrations were unaffected.

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38 – 1. AIR POLLUTION MITIGATION STRATEGIESBel and Rosell (2013) measure the impact of changes in speed limits in Catalonia by sampling datafrom the air pollution monitoring network before and after changes to speed limits in the region. Changes
in government resulted in a complicated sequence of changes in to the limits. In July 2007 the regional
government of Catalonia passed an Action Plan for Improving Air Quality in the Barcelona Metropolitan
Region, which included a reduction in the maximum speed limit to 80 km/h on motorways. Limits werereduced from 120 and 110 km/h to 80 km/h for the region, although roads were already limited to
80 km/h or lower in Barcelona. This policy was overturned in 2011 but at the same time the national
government reduced maximum speed limits from 120 km/h to 110 km/h. The 2007 Action Plan included
an experiment with variable speed limits on the two southern access roads to Barcelona that began in
2009. The variable limits adjust to traffic congestion, weather, crashes and other incidents that affectflow in real time to maintain as smooth a traffic flow as possible. Speed limits are signalled on variable
message signs and enforced by radar and automatic fines. Speeds are adjusted in increments of 10 km/h
between 80 km/h maximum and 40 km/h minimum. The new government progressively extended thesystem to other main roads at the same time as overturning the general 80 km/h limit. Bel and Rosell
found the generalised 80 km/h limit to be counterproductive but the variable speed limits highly effectivein cutting emissions, because of the reduction in stop-go traffic conditions on top of the overallmoderation of speeds. The variable speed policy was found to have reduced NOX and PM10
concentrations at monitoring stations near the controlled roads by 7.7 to 17.1% and 14.5 to 17.3%
respectively.
Dijkema et al. (2008) assessed the impact on air quality of lowering speed limits on the motorways
around Amsterdam. In November 2005, the national Transport Ministry reduced the maximum speed
limit on specific sections of urban highway from 100 to 80 km/h. The national maximum speed limit forheavy-duty vehicles was already 80 km/h. The National Transport Research Center estimated emission
reductions would be 14% for PM10 and 10–15% for NO2 leading to an improvement in atmosphericconcentrations of 0.5–1% for PM10 and 2–4% for NO2 adjacent to the ring road. The Dijkema study
assessed the impact of the speed limit change with data from the air quality monitoring network before
and after the change, adjusting for differences in weather and traffic flows. The study found reductions inparticulate matter emissions on all parts of the road network, probably related to incentives for cleanercars, but much larger reductions in PM10 and black smoke at the road sections with the lower speed
limits. The observed reduction in the mean roadside concentration of PM10 at the speed controlled
sections was 7%, much larger than predicted by the model. This might even be an underestimate as anoise wall was installed at the test site just prior to the introduction of the speed limit; the wall probably
acts to raise concentrations of particulates close to the road. In contrast to particulate matter, no clear
effects on nitrogen oxides were observed but confidence intervals were wide, owing to the highday-to-day variation of the measured NOX concentrations. Overall the authors conclude that the study
demonstrates a significant reduction of PM10 and PM1.0 as a result of reducing the speed limit at the urban
ring road.
In France, the impact of speed limits on air pollution has been measured around the western city ofRennes, where speed limits on the city’s ring road and link motorways were reduced in 2016 from 110 to
90 km/h to reduce air pollution. This followed a year of experimentation during which sections of theroads were also limited to 70 km/h. Impacts on noise, air pollution, congestion and crashes wereassessed. The reduction of speeds to 90 km/h saw NO 2 emissions fall by up to 40% whilst reductions to
70 km/h saw mixed results. As a result 90 km/h has been adopted as the limit across the network.
In the United Kingdom, Highways England is considering a 60 mph (96 km/h) limit on motorways
around Sheffield and possibly other cities to reduce air pollution, following a draft report from the
National Institute for Health and Care Excellence in December 2016 (NICE, 2016). The report concluded
that accelerating or decelerating too rapidly leads to inefficient driving and fuel consumption withSTRATEGIES FOR MITIGATING AIR POLLUTION IN MEXICO CITY — © OECD/ITF 2017

1. AIR POLLUTION MITIGATION STRATEGIES – 39

harmful emissions being released into the environment unnecessarily and sets out guidance on a strategic
range of evidence-based practical measures to encourage low or zero emissions transport. The focus of
the draft guidelines is on a local level, where actions taken by councils and transport providers will havea greater impact across local communities. The guidelines cover planning, clean air zones, congestion
charging, reducing emissions from public transport and government fleets, smooth driving and speed
reduction and cycle routes. In addition to lowering speed limits on urban motorways the report suggests
more 20 mph (32 km/h) speed limits in congested residential areas, re-designing speed bumps to stopcars speeding up and slowing down between them, restrictions on engine idling during short stops suchas outside schools and hospitals, more charging points for electric cars in residential areas and training
drivers to be more fuel efficient by driving more smoothly. The NICE report includes a review of
evidence on the efficacy of such measures. Mandatory air quality objectives
Mandatory air quality objectives have been a useful tool for improving air quality in the UnitedStates, in the form of National Ambient Air Quality Standards Non-Attainment Areas. Air quality limits
were set and a timeframe for attainment agreed, with penalties for non-compliance in the form of
withheld federal funds for non-compliant cities. This drives negotiation over budgets within local
government for measures to meet the objectives and provides the framework for communicating on theissue.
Similarly the European Union’s Ambient Air Quality Directive requires national governments for
air quality management areas in regions where standards are not met and sets timeframes for
improvement. Member States that miss deadlines are ultimately liable to substantial fines. The system
might be adopted in Mexico where the ZMVM is not the only metropolis to suffer chronic air pollution
problems but the only region to have adopted an air quality management and pollution alert system.

Enhancing and promoting sustainable transport alternatives
Containing demand for private car use and providing good quality alternatives through public
transport and cycling is an essential part of strategies to limit air pollution. Planning land use
development around investments in public transport is fundamental to limiting the growth of transportdemand as the metropolitan population increases and incomes rise. Creating urban environments that are
more accessible on foot and by non-motorised modes of transport also alleviates the need for using cars.
Metropolitan co-ordination
The lack of integrated, long-term transport and spatial planning in the ZMVM has been central tocreating unmanageable sprawl and car-dependency that exacerbate congestion and pollution. To reverse
this trend, improving co-ordination between jurisdictions and between authorities in charge of different
modes of transport is a first-order priority. In addition, integrating planning of transport and land-use isalso key.
International experience has shown that transport authorities that plan and regulate mobility acrossthe whole of a metropolitan area and have authority over different transport modes tend to be more
successful. This kind of authorities has been developed in London, Paris, Singapore and Curitiba, forexample. In Mexico the national legal framework does not allow this possibility, although proposals tomodify the law that regulates human settlements in this direction have already been put forward. In themeantime, improving the current metropolitan framework to co-ordinate planning and policy
implementation should be prioritised.

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40 – 1. AIR POLLUTION MITIGATION STRATEGIESMetropolitan governance for transport in the ZMVM was supposed to be led by the Metropolitan
Commission for Transport (COMETRAVI), which was created in 1994 and had objectives such as
improving transport services and road infrastructure in the metropolitan area, promoting standardisationof legal frameworks for transport, and providing information for the development of a Transport Master
Plan for the ZMVM. However, the commission fell short in meeting its objectives and its activities are
currently suspended. Restoring this institution would be important to construct an effective metropolitan
framework for transport planning and policy implementation.
One shortcoming with the COMETRAVI was the lack of permanent staff and financial resources.
Ensuring that these two elements are part of a restored Metropolitan Transport Commission will be key.
The institution would of course need to be effectively co-ordinated with CAMe activities and build on
the standardisation of transport-related policies across the CAMe region that this institution has alreadyadvanced. As an alternative to restoring the transport commission, CAMe could be assigned theobjectives that were originally set for COMETRAVI. In this case, adequate human and financial
resources for carrying out the corresponding activities should be assigned to CAMe.
Among the key pending issues related to metropolitan governance are:

Harmonising the legal frameworks across the ZMVM. A New Mobility Law for Mexico City
was issued in 2015 that explicitly resets priorities for allocating investment and road space infavour of pedestrians, cyclists and public transport, then freight delivery and lastly private
vehicles. Legal frameworks across the ZMVM also need to reflect these new priorities.

Integrating transport services across jurisdictions. Co-ordination between the authorities in the
ZMVM is needed to develop a metropolitan wide transport network, fostering physical,
operational and financial integration across modes and corridors that cross multiple
jurisdictions, including the Metrobus and Mexibus BRT systems, priority bus corridors and themetro. Reconfiguration of bus routes according to origin-destination demand, regardless ofadministrative boundaries is also needed.



Development of a Mobility Master plan for the ZMVM. All major conurbations in Europe now
have long-term urban transport development plans contiguous with their commuting
hinterlands. A Mobility Master Plan for the ZMVM has yet to be completed. This is key tosetting out a long-term, shared vision for more sustainable mobility and identifying the fundingthat will be needed to deliver it. Funding allocation, both from local administrations and federal
funds (Fondo Metropolitano, PROTRAM) should be linked to the priorities set out in the plan
(OECD, 2015).

Improving co-ordination between transport and land-use authorities
An important short coming for urban development in the ZMVM has been the persistent division
between spatial and transport planning. In particular the development of poorly connected, isolated andlow-density housing in the peripheries has generated high shares of long-distance trips that are served byeither highly polluting microbuses or cars (in many cases relatively old and also highly polluting). The
lack of integrated transport and land-use planning has also resulted in high and unanticipated costs forthe population. In some peripheral areas of the ZMVM (e.g Huehuetoca and Zumpango), lack oftransport accessibility has played a crucial role in a high number of homeowners abandoning houses on
which they had already started paying monthly credit fees. In addition this has placed unnecessaryfinancial stress in transport systems like the suburban rail, that due to the lack of adequate
complementary land-use planning operate at significantly lower than projected demand.

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Linking construction permits to the conclusion of agreements with developers on strategies togenerate sufficient transport capacity and cope with negative impacts on traffic and air pollution iscentral to integrating land-use and transport planning. The New Mobility Law for Mexico City
introduced mobility impact assessments for this purpose; effective development of this framework,
making it an integral part of the process for awarding construction authorisations, will be important. This
will require co-operation between the City’s Ministry of Urban Development and Housing and theMinistry of Mobility.
Financial capacity for investing in sustainable mobility
Authorities in the ZMVM also need to enhance their financial capacity for investment in public
transport and in walking and cycling infrastructure. Public transport systems need more sustainablefunding models. Firstly, regular, planned and modest fare adjustments should replace the practice of
maintaining fixed rates for long periods followed by unexpected increases. This will provide operatorswith greater certainty for future cost recovery and allow authorities to set concession terms based on cost
structure rather than by negotiating fixed levels of profits, which has contributed to financial stress in bus
rapid transit projects. Secondly, replacing generalised subsidies with targeted subsidy schemes could
help reconcile quality and affordability. Following other cities in Latin America, the ZMVM could
benefit from the introduction of smart cards to deliver subsidies for travel to lower income and othervulnerable groups. The framework developed by Mexico’s Prospera poverty alleviation programme
could be used to identify beneficiaries. Tariffs that differentiate between peak and off-peak travel would
also improve financial sustainability.
Overall, a more transparent and balanced model for subsidising public transport is required. Fundingis currently characterised by two extremes: repeated calls on “temporary” funding for projects that had
been expected to operate without subsidies, as is the case in various BRT corridors; and higher thannecessary overall levels of subsidy based on overestimates of needs for large segments of the population,
who could pay rates closer to cost-recovery. The relatively low contribution from fare box revenues
undermines budgets for maintenance and upgrades, particularly for the metro.
The funding base for investment in sustainable transport might also be enlarged by earmarking
revenues from charges on private vehicles (fines for contravening HNC restrictions and parking fees, aswell as any future charges linked LEZs or road pricing schemes). Lowering or eliminating the thresholds
for vehicle ownership taxes (tenencia) across the ZMVM is also important. For many years the revenues
from this tax were allocated to public transport. In 2014 the implicit subsidy from exempting cars with avalue below these thresholds amounted to about half of the gap between the resources received and theresources requested by the public company operating the metro.
Finally, authorities could make more use of land value capture mechanisms to fund public transport,
an approach used in many cities including London, for example, which uses Community Infrastructure
Levies added to business tax rates to fund specific investments. Betterment charges (contribución demejoras) have been available are since 2014 for funding pubic and non-motorised transport projects
inside Mexico City and the model could be extended to other States of the ZMVM.
Accelerating bus reform and making sure replaced microbuses are scrapped
BRT corridors were first introduced in Mexico City in 2005. Central to this has been the progressive
shift from a bus system operated by a large number of small under-regulated operators to one run bylarger and more professional enterprises which are now subject to higher quality and safety standards.
The process has also brought important environmental and air quality benefits since funds from the

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vehicle substitution programme have been used to incentivise the substitution of high polluting
microbuses previously operating in the corridors with BRT buses.
Overtime, the BRT system in Mexico City (Metrobús) has been expanded (six corridors are now
implemented). A similar system (Mexibus) has been implemented in municipalities of the State of
Mexico in the ZMVM (four corridors). In addition several Bus Rapid Service corridors (bus services
with preferential right of way) are being introduced in Mexico City. Making sure that microbuses
replaced are effectively scrapped has been a challenge in the expansion of the BRT system and theintroduction of BRS corridors, compromising air quality and environmental objectives. In addition,although the ZMVM has made important progress, shifting the whole of the microbus system into newconcession rules is still far from completion. Microbuses still account for the majority of total public
transport trips in Mexico City, and thus are important contributors to air pollution. In line with theobjective of advancing bus reform, the New Mobility Law in Mexico City establishes that new bus
concessions can only be granted to companies.
Accelerating bus reform throughout the ZMVM is an important priority. It is in particular relevant
to make sure scrapping of microbuses operating in routes that are shifted to operation by more
professional and regulated companies are effectively scrapped.
Among the main challenges to continue bus reform are the following is building on regulatory
expertise acquired and continuing to expand it. As in other cities that are going through bus reform,
negotiations with incumbent operators have proven challenging. Concession terms agreed have in manycases compromised financial sustainability of the system. In particular payment for operation toconcessionaires has tended to be agreed under the logic of ensuring pre-reform revenues to incumbent
microbus operators (now incorporated into the companies in the new systems) rather than based on an
evaluation of operation costs. Nevertheless, in the case of Mexico City, terms agreed by the public
regulator (also called Metrobús) have shown adjustments in the right direction as new corridors havebeen implemented, which reflects the progressive expansion of regulatory capacity. In this case having a
regulatory body with specialised staff has been an asset.
Expansion of Mexibus, as well as of BRS systems and other feeder services that will make part of
the new bus system will need to build on this experience. Co-ordinating regulation of all the different
services will be a relevant challenge, especially since, on the one hand, there is a multiplicity of
regulatory agencies in Mexico City: the BRT system is regulated by Metrobus; BRS and other new bus
services are meant to be regulated by a new institution (the Regulatory Body for Transport, ORT), andthree other entities are in charge of the metro, trolley-buses and existing publicly owned buses. On theother hand in the State of Mexico no specialised regulatory agency has been set up for new transport
services. In the short-run effective co-ordinated mechanisms should be established through: a) the
Committee for the Integrated Public Transport System, which has been created under the New Mobility
Law for Mexico City and has been assigned responsibility to co-ordinate planning and regulation of allservices operated in Mexico City; and b) the restored Metropolitan Transport Commission or CAMe, toensure coordinated regulation between services across the ZMVM.
Establishing clear rules for granting concessions and setting and adjusting tariffs is a second
challenge. BRT concession terms remain highly discretional. Moving towards concession terms based ona solid methodology built on benchmarking of operating costs to determine cost-recovery rates andnecessary subsidies if needed is key. In addition, while social and political contexts can set challenges,
moving to an open and competitive tendering process for granting concessions must remain an objective,
and a clear schedule for this must be established. During the transition period, authorities can encouragecompanies formed by incumbent operators to meet similar conditions as those they would encounter in a

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scenario with open competitive tendering (e.g. setting cost and performance information requirements,
and/or introducing quality incentive contracts similar to those used by Transport for London). Also,
while not effectively an open competition; authorities could set competitive tendering between existing
companies for tendering future corridors, as it is done in Bogotá.
The new system needs to serve origin-destinations adequately. While not meeting high quality,
safety and environmental standards, microbuses account for a high share of trips and provide services ina huge area of the ZMVM. Any transition to a system with better rationalised routes and higher quality
standards must also make sure that origin-destination trips are served and provide alternatives to groups
that risk being cut-off from transport services.

Communication strategies
Comprehensive policies for mitigating air pollution involve short term costs for parts of the
population that naturally produces opposition. Generating support for traffic restrictions and new charges
or taxes is challenging. Designing effective communication strategies to accompany this type of measureis important and can be decisive for effective implementation and sustaining measures introduced rather
than reversing policy in response to disapproval.
Surveys conducted in four mid-sized European cities that either introduced congestion charging
systems (Stockholm and Gothenburg) or had developed solid plans to do so (Helsinki and Lyon) are
instructive in regard to messages that can be central to support for traffic restrictions and demand
management measures (Eliasson, 2015). Firstly, effective communication strategies need to address
public perceptions from two perspectives present in every individual: 1) the consumer perspective (orself-interest), i.e. direct impacts on time, money, convenience, etc.; and 2) the citizen perspective, or theindividuals’ view of social issues such as equity, procedural fairness and environmental concerns that arelinked (or seen as linked) to a given policy.
Regarding the consumer perspective, a key finding is that the price that an individual will pay as aresult of a new policy is very important for determining the support that he/she will give the policy.
Nonetheless, the relationship between the price paid and the opposition to the policy is not linear; thegreatest shift from a supportive to an opposing attitude occurs between those not paying and those paying
something. Beyond this threshold opposition grows more slowly when moving to those groups that will
pay the most. Other perceived costs and benefits are also relevant and could in some cases off-set the
impact of price in the attitude towards the policy. In the case of congestion charging, time savings
appeared to be highly valued. Correctly identifying the costs and benefits of a policy for different groups
is therefore important for authorities to pinpoint initial opposition or support. In turn, the strategy forcommunication must identify and highlight benefits that are highly valued by individuals.
In terms of the citizen’s perspective, support or opposition is dependent on attitudes towards theperceived objective of the policy, the rules set by the policy and trust in the government. Messages
communicated on the strategy should take on board the following lessons regarding each of these factors(ITF, 2017):


The perceived objective of the policy: Communication strategies need to ensure that policies
implemented with the objective of improving air quality are effectively perceived as such,rather than as measures intended to raise revenues. In particular, if the scheme is seen as a tax it
will be closely linked to perceptions of taxes in general and especially where residents thinktaxes are too high and/or badly used acceptance of the policy will be undermined. To achieve
clarity on the objective of congestion charging both London and Stockholm invested heavily in

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information campaigns to prepare citizens for implementation. In both cases, the introductionof the scheme was discussed as part of a wider long-term plan with clear objectives for air
quality improvement.
The rules set by the policy: Introducing new measures often means introducing new rules, suchas restricting access to road space in areas that used to be accessible to all or, as in the case of acongestion charge, introducing a price for the use of the resource. Individuals often initiallyconsider these new rules unfair. Communication strategies can play a crucial role in changing
this perception by firstly establishing the need for rationing a resource to achieve the objective
and then explaining the advantages of the measure chosen over other mechanisms. Results fromthe surveys carried out in the four cities showed that individuals had a general tendency toconsider introduction of a pricing mechanism to restrict driving access as unfair until facedwith the task of recommending a better option (alternatives included queuing, government
allocation, and a lottery).



Trust in the government: Even when the main purpose of implementing traffic restrictions andcongestion or environmental charges is not raising revenue, these are not necessarily revenue
neutral. Attitudes to the government’s trustworthiness in allocating any revenues raised are also
a determinant of support or opposition. It is important to make clear that the main objective is
not to raise revenues. It is also useful to communicate that any revenues raised will be used in a
way that makes sense to the population. Investing this revenue in improving sustainabletransport alternatives has shown to be effective for increasing acceptance, both because
investing in these modes is seen as positive for attaining air quality objectives and because
providing good quality transport alternatives to the car is seen as equitable.

In cases like London and Stockholm improving public transport in step with implementing traffic
restrictions helped gain the support of the population. In London bus capacity was increased by 24% onroutes affected by the congestion charge. In Stockholm, EUR 170 million were spent on new buses.
Stockholm set a seven-month trial period which helped dispel public scepticism, leading to positive
support in a referendum for making the charge permanent. In London, the contest for re-election of the
Mayor was seen effectively as a referendum on the congestion charge because of its prominence among
the policy initiatives taken; the Mayor was re-elected (ITF, 2010).
International experience also shows that to be successful, communication strategies need to createawareness of the health risks of contaminated air and establish a clear relationship between air quality
and the measures chosen to cut pollution. Various tools have been developed in London to achieve thisand motivate behavioural change. Pollution information alerts are issued the day before high levels of air
pollution are forecast, with advice on how to minimise exposure risks. Alert information is displayed on
variable message road signs with instructions to switch engines off when stationary to reduce emissions.
Alert information is also displayed at bus stops on the signs that indicate waiting time and at theentrances to underground stations. Information on TfL’s website provides details of new policies being
considered and their estimated impacts well in advance of implementation. Public consultations onprospective measures are a key component. Special communications programmes targeting selectedgroups have also been undertaken with the aim of creating awareness of particular health risks andresponses for avoiding them. For example, campaigns to encourage taxi drivers to avoid idling bydeploying people to talk to drivers at taxi ranks.
Paris set up a “citizen jury” consisting of 20 people, representative of a broad range of people, whowere provided with detailed information on health issues related to pollution and possible mitigation
strategies over four days. The results of this pilot exercise showed that the public was generally poorly
informed and that once citizens discovered the impacts of pollution they supported behavioural change
and many of the proposed measures: lowering speeds to 30 km/h, a car-free day, public transport
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investment, expansion of protected bike lanes, implementation of shared electric bikes, expansion of theelectric car sharing scheme, shared electric vans for last mile deliveries, education programmes forschools and enforcement on the basis of on-road emissions monitoring. In addition to social networks
and the media, Paris also communicates using a large hot air balloon that offers rides to the public in apark in the inner city; the balloon changes colour according to the concentration of pollutants in the air,providing a constant reminder of the purpose of pollution counter-measures.
Figure 1.5. Paris’ Clean Air Balloon

Note: The balloon takes tourists for rides. The monuments depicted on the balloon change colour with the quality of the air:green in good quality air, passing through yellow and orange to red when air quality is bad.
Source: Ballon de Paris, http://www.ballondeparis.com/fr/ballondeparis/i12-la-couleur and Meet my Paris, http://www.meet-myparis.fr/visiter-paris-de-maniere-insolite/

Recommendations
Mexico City and the ZMVM have developed stringent air pollution mitigation measures with afairly comprehensive set of measures similar to policies developed in some cities in other OECD member
countries. Radical solutions to pollution from mobile sources, such as large-scale electrification oftransport, are expensive and will take time but a series of measures can be taken to strengthen, modify
and improve implementation of the air pollution mitigation measures adopted in the metropolis andnationally. The two measures with the most potential in the short term are reducing speeds on trunk roads
and reducing the sulphur content of fuel.
Immediate steps
Implementing traffic management measures that bring vehicle speeds to more constant levels
on motorways and ring roads is the most effective approach available to local governments for
reducing traffic emissions. Speed limits are an important part of these measures and produce
immediate reductions in emissions at very little cost. The 80 km/h speed limit on urban

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motorways and ring roads introduced in Mexico City in 2015 should be adopted across the
ZMVM and enforced to ensure vehicles operate in the 50 to 90 km/h range in which emissions
control technologies work best. Limiting speeds to below 80 km/h also helps maintain free flow
traffic for longer as congestion builds.


Improving fuel quality by reducing sulphur content would immediately reduce emissions fromall vehicles on the road. Ultra-low sulphur gasoline and diesel are available. International
experience suggests that tax differentiation to ensure that the price at the pump of ultra-low
sulphur fuels is competitive would produce a shift to 90% clean fuels in the space of one or two
years.

The Federal Environment Ministry has proposed adopting EPA 2010 / Euro VI emissions
standards for heavy-duty vehicles for introduction in 2019. A decision has been delayed while
the potential value of transitioning through Euro V standards is assessed. Given the very small
reductions in emissions achieved in practice on the road by Euro V standards in Europe and thevery large improvement achieved with Euro VI standards, the deliberations should conclude
rapidly that a transition through Euro V standards would be counterproductive and Euro VI
standards should be agreed on without further delay for implementation as early as possible.



Maintain both on-board diagnostic (OBD) testing of emissions and tailpipe exhaust gas testingunder the mandatory vehicle inspection and maintenance programme. Both are requiredconsidering their relative advantages. OBD interrogation detects deficiencies, diagnoses faults
and helps in avoiding fraud, whilst dynamic tailpipe exhaust testing ensures that emissions arewithin the current limits and can be used to reject vehicles with illegally altered OBD. Tailpipe
emission tests are also an alternative for those vehicles that do not comply with current OBD
requirements or do not have OBD. A report on the importance of both tests to achieving theenvironmental objectives of the law on inspection and maintenance should be prepared todefend the test procedure in court where it has been challenged on constitutional grounds.

Emissions control
National vehicle emissions standards


Mexico’s proposed national EPA 2010 / Euro VI heavy-duty vehicle emissions standards for
new vehicles should be adopted without delay and without transitional arrangements for the
much inferior Euro V standards. The crucial change in the Euro standard is a new on-road test
for in-service compliance with type-approval regulations, together with a more realistic test
cycle and inclusion of cold start conditions in the type approval test.



EPA Tier 3 / Euro 6 standards for new light-duty vehicles should be adopted nationally as soon
as possible and incorporated in incentives under pollution mitigation programs in the ZMVM
ahead of national implementation. The US standards are most effective in controlling fugitive
VOC emissions; the OBD II requirements under the US standards will also provide for more
effective OBD-based inspection and maintenance; the Euro 6 standard includes a particle
number limit to control emissions of ultrafine particles from gasoline direct injection engines.
In order to assure OBD homologation for all vehicles sold in Mexico, NOM–042SEMARNAT-2003 should be updated as soon as possible..

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Emission control system retrofits
Continue the bus diesel particulate filter retrofit program with strict certification and testing in
use and extend it to other vehicles including garbage trucks. Ensure an appropriate inspection
and maintenance program for these retrofit filters to prevent their removal.



Ensure certification and accreditation for retrofits of three-way catalytic converters, including
conversion efficiencies compatible with current emission standards, coverage of durability andfree replacement in case of defective performance on inspection.

Off-road mobile sources and special vehicles
Control non-road mobile machinery emissions, introducing EU regulation 2016/1628.

Extend incentives for cleaner vehicles, retrofit programs and restrictions on use during
pollution alerts to construction equipment and other off-road vehicles.

Non-mobile sources of emissions of volatile organic compoundsStrengthen measures to control emissions of volatile organic compounds from non-mobile
sources because ozone formation in the ZMVM is generally limited by these precursor
emissions and mobile sources contribute only a fifth of total emissions.

Incentives for cleaner vehicles
Incentives for purchase of EPA 2010 / Euro VI heavy-duty vehicles ahead of the new national
standards, as already applied for example through the voluntary truck inspection andmaintenance program, should be expanded, for example to buses.



EPA Tier 3 / Euro 6 standards should become reference standards for the vehicle inspection
and maintenance certification system, reserving 00 certificates for Tier 3 / Euro 6 light-duty
vehicles in the near future, even ahead of their incorporation in national standards.



Differentiate between 00 and 0 vehicle classes in the restrictions on light-duty vehicle use
under pollution alerts. Reserve the 00 class for Tier 3 / Euro 6 light-duty vehicles when thisstandard is adopted nationally for sales of new models and consider early differentiation aheadof the date the new standard becomes binding once an implementation timetable is agreed.

Differentiate the vehicle ownership tax (tenencia) according to emissions class.

Ultra-low sulphur fuels


The Federal government should introduce tax incentives for ultra-low sulphur gasoline anddiesel as switching to these fuels will produce immediate reductions in emissions from all
vehicles on the road.

Inspection and maintenanceSafeguard and continue to improve the current centralised system for homologation, quality
control and conformity of vehicle inspection centres in order to guarantee the reliability of test
results. Consider adopting California’s best practices including those to guard securely against
fraud.

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48 – 1. AIR POLLUTION MITIGATION STRATEGIESContinue with the remote surveillance, as well as periodic audits of the equipment used inemissions test centres; use of unmarked control vehicles could also be introduced as anadditional check on fraud in licenced concessions.

Continue to refine how OBD data (such as readiness indicators) are used during the inspection
process to improve inspection accuracies and to deter fraud.

Work to ensure that all inspection jurisdictions within the ZMVM apply best practices forinspection and maintenance so that motorists cannot obtain inspections of lesser stringency
depending on where within the region they seek to get their vehicle inspected.

Incorporate motorcycles into the I&M system and make them subject to vehicle restrictions.

Restricting vehicle use

The environmental benefits of regular restrictions on vehicle use under the Hoy No Circula(HNC) system should be reinforced by measures that incentivise fleet renewal and reduce
congestion. In the long term, a combination of such measures might substitute for the HNC
system outside of peak pollution episodes.



There is a case for implementing a low emissions zone that would, at least in a first phase,
focus on heavy-duty vehicles including buses and microbuses, using the current vehicle
certification and identification systems.

Light-duty vehicles could also be incorporated into a low emissions zone, with occasional use
of more polluting vehicles permitted against payment of an access fee. This would replace
access according to number plate. Charges for access to low emission zones should be set toensure regular users have an incentive to switch to cleaner vehicles and shift to public transport.

Specific mechanisms to reduce congestion will also be needed. Road pricing and congestion
charges are effective tools for this.



The CAMe should co-ordinate the development of the low emission zones already underconsideration by cities in the region to ensure restrictions are based on emissions standards andprovide incentives for the cleanest vehicles. The very small scale of the schemes currently
under consideration means they will have little impact on air quality in the ZMVM as a whole
and larger scale zones are recommended.

Modifications to restrictions should be supported by analysis of sufficient detail to identify
which categories of vehicle traffic generate most pollution and congestion and the levels of
charges needed to incentivise fleet renewal and modal shift. Ex-post evaluation of theperformance of restrictions is also important for modifying schemes and implementing
complementary policies as conditions change.

Enforcement
Use the Regional Environment Commission as a forum to negotiate reciprocal arrangements
between the States in the CAMe region for the payment of fines for contravening inspection
and maintenance regulations and restrictions on the use of vehicles.

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Traffic management
ParkingExtend the Ecoparq on-street parking controls to other parts of Mexico City and to other areasin the ZMVM.



Differentiate parking charges according to demand and availability of public transport services.



Abolish minimum requirements for off-street parking in building codes.

Speed limitsThe speed limits differentiated by road type introduced for road safety in Mexico City in 2015
should be extended across the whole of the ZMVM as in addition to cutting road trauma theytend to result in smoother traffic flow, lowered excess emissions generated in stop-go traffic,
excess acceleration and excess speed.

Enhancing sustainable transport alternatives

Renew efforts to develop a framework for metropolitan governance of transport in the ZMVM
and carry out strategic planning of public transport as set out in the 2014 PROAIRE program.
In the short run restore the Metropolitan Commission for Transport or assign its
responsibilities to CAMe, making sure adequate financial resources and permanent staff forcarrying out these responsibilities are also made available to any of these institutions.



Authorities should also work in adjusting the legal and institutional frameworks forestablishing a metropolitan transport authority for the ZMVM in the longer term.

Metropolitan governance should focus on:Harmonising the legal framework across the ZMVM, particularly to make explicit priorities
for investing and allocating road space in favour of public and non-motorised modes.

Integrating transport services across jurisdictions.



Developing a Mobility Master Plan for the ZMVM and linking funding allocation topriorities set by the plan.

Improve linkages between land-use and transport planning. Implement the property
development Mobility Assessment procedure provided under Mexico City’s 2015 Mobility
Law and link it directly to the process of awarding construction authorisations. Expand thisframework across the ZMVM.

Continue to invest in improving the quality of public transport services, including access tometro and rail stations, BRT platforms and bus stations, and continue to invest in infrastructure
for safe cycling and walking. Viable alternatives are essential to the success of restrictions on
the use of cars. To enhance the financial capacity for this investment:Move to more sustainable models for public transport tariff systems, making fareadjustments on a regular, planned basis with more modest increases rather than large,
sporadic hikes, and replace generalised subsidies with subsidies targeted to low income and

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vulnerable users. Tariffs and subsidies should be set based on solid evaluations of operating
costs and affordability of the population.



Earmark revenues from charges for the use of private vehicles, including fines for failure tocomply with the No-driving day and inspection and maintenance systems and any future
traffic restriction schemes, and also the vehicle ownership tax, to investment in public
transport and walking and cycling facilities.



Make use of land-value capture mechanisms, such as the existing betterment charge(Contribución de mejoras) for investment in public transport.

Accelerate bus reform throughout the ZMVM and where agreements are made to scrap
microbuses and operate routes under consolidated concessions with higher standard vehicles,
ensure the old vehicles are actually scrapped and do not continue to be used in competition with
the new services.

Air quality management plansThe Federal government should establish air quality monitoring systems and management plans
for areas in Mexico beyond the ZMVM that do not meet national ambient air quality standards.

Communication
Run campaigns to raise awareness of the health risks of contaminated air, the steps individuals
can take to reduce air pollution, and the investments made by government to provide
alternatives to the use of polluting vehicles, including public transport.



Invest in information campaigns to prepare citizens for modifications to pollution mitigation
policies, stressing the air quality and health benefits targeted. Once revenues are earmarked toflanking measures such as investment in public transport, this should also be stressed.



Subject policy proposals to public consultation.



Report regularly on the achievements of the policies adopted.

These recommendations, although not exhaustive, cover the broad range of measures that should betaken. Table 1.8 maps the different measures according to the broader policy category to which they
belong, as well as the time frame for implementation. For the purpose of the table, short, medium andlong term correspond to the periods of 1-3 years, 3-5 years and 5-10 years respectively. Whilst this report
does not attempt cost benefit analysis or a regulatory impact assessment of the measures, a rough idea of
their potential, relative costs and the timeframe over which they yield benefits, as well as particularchallenges and additional steps needed is also provided in Table 1.9.

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Table 1.8. Map of recommended measures and time frame for implementation
Short term (1-3 years)

Medium term (3-5 years)

Emissions control
Implement national HDV Euro VI
Adopt national HDV Euro VI
standard.
standard.
Implement national LDV EPA Tier
Adopt national LDV EPA Tier
3/Euro 6 standard.
3/Euro 6 standard.
Introduce EU regulation 2016/1628
Develop an I&M for Bus DPF
for non-road mobile machinery
Retrofit.
Certification and accreditation for LDVemissions.
retrofits (three-way cc).
Extend incentives for cleaner
technologies and restrictions on use
during pollution alerts toconstruction and off-road sources.
Negotiate tighter VOC standards fornon-mobile sources.
Incentives for clean vehicles
Incentives for purchase of Euro VI /EPA Differentiate vehicle ownership tax
according to emission class.
2010 buses.
EPA Tier 3 / Euro 6 standards reference
for “00” category in I&M anddifferentiate between “00” and “0”classes in restrictions on vehicle use
under pollution alerts.
Fuel quality
Introduce tax incentives for ultra-low
sulphur gasoline and diesel.
I&M
Introduce periodic audit and use ofunmarked control vehicles.

Introduce test result centralisation
into the I&M system.

Incorporate motorcycles.
Maintain primary reliance on OBD
testing and develop support to defend
this in court.

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Long term (5-10 years)

52 – 1. AIR POLLUTION MITIGATION STRATEGIES

Table 1.8. Map of recommended measures and time frame for implementation (continued)
Short term (1-3 years)

Medium term (3-5 years)

Long term (5-10 years)

Implement LEZ for HDV
including buses and microbuses.

Incorporate LDVs andmotorcycles to the LEZ in
combination with roadpricing/congestion charges.

Vehicle use restrictions

Use HNC restrictions forpollution episodes only.
General Traffic Management
Expand speed limits to the whole of the
ZMVM.
Extend Ecoparq on-street parking
controls to the whole of the ZMVM.

Abolish minimum requirements foroff-street parking in building
codes.
Set differentiated parking charges.

Enforcement
Use CAMe to negotiate reciprocalarrangement for the payment of fines forcontravening I&M regulations,
restrictions on the use of vehicles, andother traffic regulations.

Air quality plans
Establish air quality monitoring
beyond the ZMVM and require
management plans for areas that do
not meet national ambient air
quality standards.

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1. AIR POLLUTION MITIGATION STRATEGIES – 53

Table 1.8. Map of recommended measures and time frame for implementation (continued)
Short term (1-3 years)

Medium term (3-5 years)

Long term (5-10 years)

Make the necessary adjustments inthe national legal framework toallow establishing Metropolitan
Transport Authorities.

Establish a Metropolitan
Transport Authority for theZMVM.

Enhancing and promoting sustainabletransport modes
Restore COMETRAVI or assign its
responsibilities to CAMe (with adequate
staff and financial resources).
Work on harmonising legal frameworks,
integrating transport services acrossjurisdictions and in developing a Mobility
Master Plan for the ZMVM.
Implement the property development
Mobility Assessment (in Mexico City’s
2015 Law) and link it to the process ofawarding construction authorisations;
expand across the ZMVM.

Replace generalized subsidies withsubsidies targeted to low income
and vulnerable users.

Move towards public transport tariffs withregular and planned fare adjustments.
Develop solid methodologies for calculating
costs and affordability and determine theExplore use of other land value
need for subsidies accordingly.
Earmark revenues from private vehicle
charges (including fines for noncompliance with I&M and HNC) toinvestment in public and active modes.

capture mechanisms for investingin public transport and activemodes.

Make use of betterment charges for public
transport investments.
Accelerate bus reform and ensure
microbuses replaced are effectively
scrapped.

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54 – 1. AIR POLLUTION MITIGATION STRATEGIES

Table 1.9. Summary of recommended measures and responsible authorities
MeasureDecision andimplementation
time frame

Responsible
authorities

National HDV EPA2010 /Euro VI standard
National LDV EPA Tier3 /Euro 6 standard
Restrictions on non-road
machinery during alerts
I&M for Bus Retrofits

Short

SEMARNAT

Short

SEMARNAT

Negotiation with car industry

Short

CAMe/States

Short

StatesCertification andaccreditation for retrofits LDVs
Non-road mobile machinery
emissions standards
2016/1628/EU
Tighter control of nonmobile VOC sources
Euro VI/EPA 2010 bus
incentives
I&M class revisionI&M 00-0 classdifferentiation
Vehicle ownership tax
differentiation

Short

States

Negotiation withconstruction industry
Negotiation withconcessionaires
Quality assurance

MediumSEMARNAT

Short

CAMe

Short

States

Short
Short

CAMe
CAMe

Short

StatesFuel quality

ULS fuels

Short

SEMARNAT

I&M

I&M audit and checking

Short

CAMe/States

Incorporate motorcycles
into I&M and vehicle
restrictions
I&M test result
centralisation

Short

CAMe/States

MediumCAMe

Emissionscontrol

Incentives
for cleaner
vehicles

Challenges and additional
steps

Negotiation withconstruction and vehicleindustry
Negotiation with a range ofbusinesses
Negotiation with bus
concessionaires
Communication with public
Communication with public
Communication with public,
fiscal neutrality or
earmarking
Achieving fiscal neutrality

Introduce in conjunction withthe renewal ofconcessionaires for I&M
testing
Communication with the
publicNegotiation with I&M
concessionaires

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Table 1.9. Summary of recommended measures and responsible authorities (continued)

Restrictions
on vehicle
use

Generaltraffic
management

MeasureDecision andimplementation
time frame

Responsible
authorities

Challenges and additional
steps

Wide scale LEZ for HDVs

MediumStates/CAMe

Wide scale LEZ for all
vehicles with HNC
restrictions used forpollution episodes only

Long

CAMe

Road pricing/congestion
chargeLong

StatesSpeed limits

Short

StatesEcoparq extension

Short

States

Effective communication
with public.
Design based on detailed
analysis ofrestrictions/charges on fleet
renewal and ultimately on
pollution.
Consideration of possible
economic negative effects
and action to mitigate them.
Effective communication
with public.
Design based on detailed
analysis ofrestrictions/charges on fleet
renewal, modal shift andpollution.
Consideration of possible
socio-economic negative
effects and plan for actions
to mitigate them.
Design based on detailed
analysis for estimated effects
of charges on travel
behaviour and modal shift,
and ultimately oncongestion.
Consideration of possible
socio-economic negative
effects and plan for actions
to mitigate them.
Effective communication
with public.
Effective communication
with public.
Co-ordination between landuse and transport authorities.

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Table 1.9. Summary of recommended measures and responsible authorities (continued)
MeasureDecision andimplementation
time frame
MediumResponsible
authorities

Challenges and additional
steps

StatesEnd minimum parking
requirements in buildingcode

MediumStatesEnforcement

Reciprocal enforcementof fines

Short

States/CAMe

Effective communication
with public.
Co-ordination between landuse and transport authorities.
Removal of legal barriers.
Effective communication
with public.
Co-ordination between
authorities in charge of landuse and transport.
Communication with the
public.

Air quality
plans

National air quality
monitoring andrequirements for
management plans forareas that do not meetnational air quality
standards
Restore Metropolitan
Commission forTransport or assign its
responsibilities to CAMe
Develop the Mobility
Master Plan for the
ZMVM

Short

SEMARNAT
and States

Negotiation with the States

Short

FederalGovernment
and States in
the ZMVM
States plus
Metropolitan
Commissionin charge

Agreement of States toallocate adequate resources
and assign dedicated staff.

Operational and financial
integration between
transport modes andacross State boundaries
in the ZMVM
Property development
mobility assessment
procedure

MediumStates plus
Metropolitan
Commissionin charge

Long

Introduce tariff systems
with regular and planned
fare adjustments

Short

States (landuse andtransport
authorities),
Metropolitan
Commission
StatesGeneraltraffic
management(continued)

Enhance andpromotesustainabletransport
modes

Differentiated parking
charges

MediumData collection andimproving analysis tools.
Co-ordination withTerritorial Plan (POZMVM).
Link fund allocation (federal
and State funds) to priorities
set by the Master Plan.

Communication withproperty developers.

Communication with public.

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1. AIR POLLUTION MITIGATION STRATEGIES – 57

Table 1.9. Summary of recommended measures and responsible authorities (continued)

Enhance andpromotesustainabletransport
modes(continued)

MeasureDecision andimplementation
time frame

Responsible
authorities

Challenges and additional
steps

Shift from generalised totargeted subsidies

MediumStatesEarmark charge and finerevenues to public
transport
Betterment charges forsustainable transport
investment
Explore other land value
capture mechanisms

Short

StatesDevelop framework foranalysis on affordability(could build on Prospera
programme) and linking
smartcards to award of
subsidies.
Negotiation with fiscal
authorities.

Short

StatesMediumEstablish a Metropolitan
Transport Authority for
the ZMVM

Long

FederalGovernment
and States
FederalGovernment
and States

Accelerate bus reform
and make suremicrobuses are
effectively replaced andscrapped

Short

STRATEGIES FOR MITIGATING AIR POLLUTION IN MEXICO CITY — © OECD/ITF 2017

StatesCommunication withproperty developers.

Adjust legal and institutionalframework for allowing
establishment of
metropolitan transport
authorities.
Negotiation with bus
concessionaires

58 – 1. AIR POLLUTION MITIGATION STRATEGIES

Figure 1.6. Broad indication of relative impact and cost of selected measures
Impact

Wide
scale
LEZ

Euro VI
Euro VI
EPA2010 HDV EPA2010 bus
standard
incentives

Vehicleownership tax
differentiation
I&M classmigration

Non-road
machinerystandard

ULSG
limit

Non-road
machinery alert
restrictions

LDV
HC traps
Speedlimits

ULSD
limit

Non-mobile
source VOC
controls

HDV
retrofits

Tier 3 / Euro 6
LDV standard

Reciprocal
fines

Cost

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2. AIR POLLUTION AND MITIGATION MEASURES IN MEXICO CITY TODAY – 59

2. Air pollution and mitigation measures in Mexico City today
Introduction: The current situation and the high ozone concentration episodes of 2016
The World Health Organization (WHO) estimates that in 2012, air pollution in Mexico caused
17 000 premature deaths (WHO, 2016). In Mexico City (just the central part of the metropolitan area), it
is estimated that if the WHO recommendations on air quality were observed, more than 1 400 of these
deaths could be avoided each year (INECC, 2016b). A series of measures have been taken to address thisserious public health problem, which has considerably reduced pollutant concentrations in comparison to
those observed in the mid-80s and the beginning of the 90s. However, despite the improvements
observed in lead, carbon monoxide (CO), sulphur dioxide (SO2) and nitrogen dioxide (NO2)concentrations, air quality standards for ozone and for PM10 and PM2.5 particulates have not been met,
and air pollution is still a challenge for both authorities and inhabitants.
Geographic and institutional context
The Metropolitan Area of Valle de México (ZMVM) is situated in the central area of the country ina basin with an altitude of between 2 200 and 2 800 metres above sea level, and surrounded by mountainelevations that reach above 5 000 metres (INEGI, 2014). This situation contributes to the generation ofhigh pollutant concentrations. The altitude reduces the efficiency of combustion processes, the relief
makes the dispersion of pollutants difficult and the intensity of solar radiation fosters the formation ofozone and other secondary pollutants.
Box 2.1. Metropolitan Area of the Valle de Mexico









20.1 million inhabitants
Motorisation index: 250 vehicles per 1 000 inhabitants in 2014
5.3 million vehicles: 80% private (cars, SUVs, motorcycles), 13% freight, 7% public transportation
Energy consumption: 543 PJ directly from oil products, of which over 50% are transport fuels
2 410 regulated trades and services
1 935 regulated industries (from a total of 5 200)
5 fuel storage depots
5.8 million residences

Source: Secretariat of Environment of Mexico City (SEDEMA) (2016).

Administratively speaking, the ZMVM comprises three jurisdictional entities: Mexico City
(16 territorial delegations), part of the State of Mexico (59 of its 125 municipalities) and part of the Stateof Hidalgo (one municipality). The State of Mexico’s municipalities cover the greatest territorial
proportion (6 000 km2 vs. 1 500 km2 occupied by Mexico City) and population (12.2 vs. 8.8 million
inhabitants) (SEDEMA, 2016a). This administrative division implies that strategies to combat pollution
must involve authorities from all three States as well as representatives from the municipalities. As somepollution sources are regulated by federal agencies, including Federal Environmental authorities is alsoessential.

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Co-ordination among these authorities began in 1990 with the Comprehensive Programme against
Atmospheric Pollution (Programa Integral contra la Contaminación Atmosférica, PICCA). The
programme included an air quality assessment and review of emission sources, commitments made inorder to reduce pollution (such as the introduction of catalytic converters) and a calculation of the cost ofthese commitments. Two years later, preparations began for a commission to co-ordinate the institutions
at all government levels to combat pollution. Finally, in 1994, the Metropolitan Environmental
Commission (Comisión Ambiental Metropolitana, CAM) was created. The commission included all
16 territorial delegations of Mexico City (then a Federal District), 18 municipalities from the State of
Mexico, and the former Secretariat for the Environment, Natural Resources and Fishing (Secretaría deMedio Ambiente, Recursos Naturales, SEMARNAT) in the Federal government.
The CAM was responsible for co-ordinating actions for improving air quality for almost 20 years,
as well as issuing the Air Quality Improvement Programmes (Programas para Mejorar la Calidad delAire, PROAIRE) for the ZMVM. In 2013 it became the Environmental Commission for the Megalopolis(Comisión Ambiental de la Megalópolis, CAMe). It now includes, in addition to the 16 delegations(boroughs) of Mexico City, every municipality within the states of Hidalgo, Mexico, Morelos, Puebla
and Tlaxcala, since they either have an impact on or are affected by the air quality of the ZMVM. The
commission is in charge of developing the Environmental Alert Programmes to address high pollutant
concentration episodes and co-ordination between State and Federal authorities to design and enforce
emission control programmes.
Box 2.2. Atmospheric Monitoring System (Sistema de Monitoreo Atmosférico - SIMAT)The ZMVM has over 40 monitoring and meteorological stations distributed between four sub-systems:

Atmospheric Monitoring Automatic Network (Red Automática de Monitoreo Atmosférico - RAMA):
Started operation in 1986. It currently has 29 monitoring stations with continuous devices to measure
SO2, CO, NO2, ozone, PM10 and PM2.5, as well as a maintenance and calibration laboratory for its
equipment.



Atmospheric Monitoring Manual Network (Red Manual de Monitoreo Atmosférico - REDMA):
11 monitoring sites with manually operated equipment for particle sampling (carried out every six days).



Meteorology and Solar Radiation Network (Red de Meteorología y Radiación Solar - REDMET):
19 sites with continuous surface meteorological variable measuring equipment for temperature, relative
humidity, wind direction and velocity, solar radiation and atmospheric pressure.



Atmospheric Deposit Network (Red de Depósito Atmosférico - REDDA): 16 sampling sites withsemi-automatic equipment used to collect dry and humid deposit samples every seven days.
The Atmospheric Monitoring System (SIMAT) is supported by the Environmental Analysis Laboratory(Laboratorio de Análisis Ambiental - LAA), formed by laboratories that perform elemental analyses, gas
chromatography, gravimetric and aerosol studies for the samples that each network collects. The Air Quality
Information Centre (Centro de Información de la Calidad del Aire - CICA) stores, validates, processes and issues
data generated by the monitoring programs.
Source: SEDEMA (http://www.aire.cdmx.gob.mx/default.php?opc='ZaBhnmI=').

Every action under these programmes is based on the air quality assessment carried out by the
Atmospheric Monitoring System for Mexico City (Sistema de Monitoreo Atmosférico de la Ciudad de
México, SIMAT). This system has continuously recorded pollutant concentrations within the Mexico
City Valley area since the late 1980s working with over 40 monitoring stations distributed around themetropolitan area of Mexico City (Box 2.2). These measurements are recorded, processed and

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communicated through yearly reports, on websites on an hourly basis, through mass media and, recently,
through a smartphone application.8 When SIMAT records concentrations that exceed the thresholds
established by the PCAA, it notifies the CAMe in order to activate the corresponding measures. The
Secretariat for the Environment of Mexico City’s Government administers the SIMAT and its component
systems, including monitoring stations located in the State of Mexico (SEDEMA SIMAT, n.d.).
Box 2.3. Websites for information on air quality and pollution counter-measures
PROAIRE

Air pollution monitoring: http://www.aire.cdmx.gob.mx/default.php?opc=Z6BhnmI=&dc=aA==

Air pollution counter-measures: http://www.gob.mx/comisionambiental

Current air quality: http://www.aire.cdmx.gob.mx/default.php?opc=%27YqBhnmI=%27
CAMe

Air quality standards and trends
The Air Quality Index (Índice de Calidad del Aire, formerly known as IMECA) is used tocommunicate air quality conditions to citizens. It is calculated based on monitoring station measurements
of atmospheric concentrations through an algorithm defined by a local regulation (NADF-009-AIRE2006). The 100-point value corresponds to the acute exposure limit defined under health protection
regulations.
Table 2.1. Air Quality Index breakpoints in Mexico and the US
AQI
0–
50
51 –
100
101 –
150
151 –
200
201 –
300
301 –
400
401 –
500

Air quality category
MX
Buena

US
Good

RegularModerateMala

Muy Mala

Unhealthy
Sensitive
GroupsUnhealthy

Extremadamente
Mala

Very
Unhealthy
Hazardous

O3(ppb 8-hour)
MX US
0
54
55
70
71
85
86
105
106
200

O3
(ppb 1-hour)
MX
US
0
70
71
95
96
125
154
164

PM10
(µg/m3 24-hour)
MX
US
0
0
40
54
41
55
75
154
76
155
214
254

PM2.5
(µg/m3 24-hour)
MX
US
0
0
12
12
12.1
12.1
45
35.4
45.1
35.5
97.4
55.4

155
204
205
404
405
504
505
604

215
354
355
424
425
504
505
604

97.5
150.4
150.5
250.4
250.5
350.4
350.5
500.4

165
204
205
404
405
504
505
604

255
354
355
424
425
504
505
604

55.5
150.4
150.5
250.4
250.5
350.4
350.5
500.4

Sources: SEDEMA, http://www.aire.cdmx.gob.mx/default.php?opc=%27ZaBhnmI=&dc=%27aQ==; US Electronic Code ofFederal Regulations, Part 58, Ambient Air Quality Surveillance,
http://www.ecfr.gov/cgi-bin/retrieveECFR?gp=&r=PART&n=40y6.0.1.1.6#sp40.6.58.f

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The index adopts the methodology developed by the US EPA, with an identical categorisation of the
Air Quality Index (AQI) but locally determined breakpoints for each pollutant. These were last updated
in Mexico for ozone, PM10 and PM2.5 in 2014 (under NOM-020-SSA1-2014 and NOM-025-SSA1-2014).
Current breakpoints for these pollutants are summarised in Table 2.1.
Although the concentration levels for most atmospheric pollutants in Mexico City are below theacute exposure limits set by health regulations, ozone and particulates concentrations still regularly
exceed national air quality regulations. Figure 2.1 shows concentration trends for ozone since 1986.
The improvement for this pollutant since 1992 is remarkable. However, as noted in the latest, 2014,
report on air quality for Mexico City ozone concentrations do not comply with regulated Mexican limits
for chronic and acute exposure (SEDEMA, 2015). Figure 2.1 also shows a slight increase inconcentrations since 2014. Figure 2.2 shows concentrations recorded within the metropolitan area
compared to limits prescribed by the Ministry of Health to protect public health, as well as those set by
the World Health Organization (WHO) and the United States’ Environmental Protection Agency(USEPA).
Figure 2.1. Trends in ozone concentrations, annual average (1986-2016)

Source: SEDEMA, SIMAT.

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Figure 2.2. Ozone concentrations vs. Mexican, WHO, and US air quality limits.
Ozone (ppb), WHO recommendation = 100 μg/m3

250
192

200

150
112

109
100
75

70
50

50

0
NOM-020-SSA1-2014(5th 8h-max)

WHO (8h max)*

Limit

USEPA (three-year
average of 4th max
conc)

Mexico City Met Area

Source: SEDEMA.

Although most recent acute pollution episodes in Mexico City are related to high ozone
concentrations, air quality concerning particulate matter is also troubling. The 2014 SIMAT report
indicates that PM10 concentrations have decreased since 1992, but they still do not comply with Mexican
health protection regulations. PM2.5 concentrations have remained practically at the same level since they
started being measured in 2004. Figure 2.3 shows trends for particulate matter concentrations andcompares them against health protection limits. It should be noted that PM2.5 and PM10 exceed chronic
exposure limits under Mexican and WHO standards.

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Figure 2.3. Annual average concentration tendencies for PM10 y PM2.5, and compliance with Mexican,
WHO and US regulation suggestions
3

PM10 (μg/m )3

PM2.5 (μg/m )Source: SEDEMA (2015).

Main pollution sources
Since ozone is a secondary pollutant, reducing its atmospheric concentration is a complex challenge.
Pollution counter-measures need to be based on an analysis of the sources of emission of precursor
gasses (nitrogen oxides and volatile organic compounds) as well as the geographic and meteorologicalconditions that promote its formation. Figure 2.4 summarises the emission sources for local pollutants
included in the most recent emissions inventory for Mexico City (2014). As can be seen, the main
sources of emissions of nitrogen oxides (NOx) are motor vehicles, contributing 80% of the emissions.
According to assessments from the Ministry of Environment for Mexico City, about 5.3 million vehicles
circulate in the Metropolitan Area of Valle de México, of which 80% are gasoline fuelled private cars,
SUVs and motorcycles, 13% are heavy-duty freight vehicles, mostly using diesel, and 7% are public
transportation vehicles (mostly diesel).
Most light-duty vehicles run on gasoline and are relatively new; 70% are between 0 and 10 years
old. These, as described in Chapter 3, comply with NOx and hydrocarbon emission limits, corresponding
to the more relaxed US Tier 2 standard limits (bins 7-10) and, for European manufacturers, Euro 3emissions standards.

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Figure 2.4. Atmospheric pollutant emissions in the ZMVM (2014)
Total emissions (tonnes/year)

Contribution to volatile organic compound emissions

Source: SEDEMA (2016a).

Figure 2.5. Ozone precursor emissions from mobile sources (tonnes/year)

100%

2 505

5 280

90%

5 950

80%

44 26314 349

70%
60%
50%

16 10740%
46 46230%
20%

45 809

10%
0%

NOx

VOC

Motorcycles
Heavy duty vehicles (trailers, transit buses, freight trucks over 3.8 tons, BRT units)

Medium duty (microbuses, pickups and trucks below 3.8 t)
Light duty vehicles (cars, SUV, vans, taxis)
Source: SEDEMA (2016a).

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Figure 2.5 shows the total emissions of precursors for ozone formation from mobile sources. As canbe seen, the contributions of light and heavy-duty vehicles to NOx emissions are roughly the same.
Whilst light-duty vehicles contribute most of the VOC emissions from mobile sources, other sources
contribute more to overall emissions (Figure 2.6). Combustion of liquefied petroleum gas releases
significant quantities of un-burnt propane and butane, mostly from residential heating (which constitutes
65% of the total consumption for this fuel). In addition, 8.6 million tonnes of solid waste is generated
every year in the city, which produce about 280 thousand tonnes of methane (SEDEMA, 2016a). The
contribution from these sources is especially important for ozone formation in the Mexico City
metropolitan area, since the scientific evidence collected on several field assessments carried out in 2006
showed that the formation of ozone in the city is very sensitive to VOC concentrations (INECC, 2016a).
High ozone pollution events
The ozone pollution season in Mexico City’s metropolitan area usually begins in late February andends in June. During these months, high solar radiation, longer daylight hours, atmospheric stability andlow humidity contribute to ozone formation and accumulation. Historically this is the period during
which the highest ozone levels have been registered, activating ozone alerts. Figures 2.6 and 2.7 illustrate
the way peak pollution levels have declined; Figure 2.6 presents a series of maps showing the highestozone concentrations recorded in 1995, 2000, 2005, 2010, 2015 and 2016, using the current air quality
index. As it can be seen, although high levels of ozone continue to be experienced, the peak levels havedecreased over time in response to pollution mitigation measures.
The ozone concentration at which the Atmospheric Environment Alert Program (Programa deContingencias Ambientales Atmosféricas, PCAA) is activated has changed over time, as Table 2.2
records. The latest modification to the PCAA included eliminating the warning, pre-alert, stage andreducing the alert activation threshold (from 180 points/185 ppb to 150 points/155 ppb).
Table 2.2. Modifications to the Atmospheric Environment Alert Program
Activation thresholds

Ozone limit

Points on the Air Quality Index (IMECA)
Pre-alert

Alert Phase 1

Concentrations equivalent to
151 IMECA points
1-hour average

2005

200

240

250 ppb

August 2012

200

240

250 ppb

October 2014

151

181

185 ppb

April 2016

Eliminated151

155 ppb

Source: SEDEMA, http://www.aire.cdmx.gob.mx/descargas/ultima-hora/calidad-aire/pcaa/pcaa-modificaciones.pdf

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Figure 2.6. High ozone events over time

Note: the number inside the circles represents the ozone hourly concentration in ppb.
Source: SEDEMA SIMAT (2016).

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Figure 2.7. Number of days on which maximum hourly ozone concentration exceeded 155 ppb(150 points on the IMECA air quality index today)

350
300

315
290

281

303
287

275

268

258 253

250

248
225
193

200

181

150

119

100

77 79
50
34 27
21 20

50

12

4

15

18

8

7

2012

2013

2014

2015

2016

04/11/2016

18/11/2016

02/12/2016

16/12/2016

30/12/2016

2011

2010

2009

2008

2007

2006

2005

2004

2003

2002

2001

2000

1999

1998

1997

1996

1995

1994

1993

1992

1991

1990

0

Source: SEDEMA.

Figure 2.8. Daily Air Quality Index during Ozone season in 2016

200

150

100

21/10/2016

07/10/2016

23/09/2016

09/09/2016

26/08/2016

12/08/2016

29/07/2016

15/07/2016

01/07/2016

17/06/2016

03/06/2016

20/05/2016

06/05/2016

22/04/2016

08/04/2016

25/03/2016

11/03/2016

26/02/2016

12/02/2016

29/01/2016

15/01/2016

001/01/2016

50

Source: SEDEMA SIMAT.

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Measures to control vehicle emissions
A number of complementary instruments have been developed in Mexico to control emissions fromthe vehicle fleet. The key mitigation mechanisms for the ZMVM are outlined in this section. At anational level, the federal government (through the Ministry for the Environment and Natural Resources,
SEMARNAT) is authorised by Mexican environmental law to issue emission control regulations for new
vehicles and vehicles in use. The Federal Attorney's Office for Environmental Protection (PROFEPA)
supervises compliance with the regulations for new vehicles. The governments of states andmunicipalities have the responsibility for enforcing regulation of emissions from vehicles in use. The
Ministry of Communications and Transport (SCT) ensures compliance with heavy vehicle emission
regulations for vehicles registered with a federal number plate. Table 2.3 shows the current regulations
for each type of vehicle.
The vehicle fleet in the ZMVM is comprised of vehicles subject to a variety of regulatory regimes
and regulatory authorities corresponding to the place where they are registered and the type of vehicle(see Figure 2.9), with the heavy-vehicle fleet particularly heterogeneous.
Figure 2.9. Vehicle distribution in ZMVM according to jurisdiction

Source: SEDEMA (2016a).

At a local scale, Mexico City has developed a Mandatory Vehicle Inspection Programme (Programade Verificación Vehicular Obligatorio, PVVO), a No-driving day programme (Hoy No Circula [HNC]),
the Environmental Atmospheric Alert Programme (Programa de Contingencias Ambientales
Atmosféricas, PCAA), the Diesel Vehicle Self-Regulation Programme (Programa de Autorregulación de
Vehículos a Diésel), an Alternate Fuel Programme (Programa de Combustibles Alternos), theComprehensive Programme for Reducing Pollutant Emissions (Programa Integral de reducción deemisiones contaminantes, PIREC) and the School Transport Programme (Programa de Transporte
Escolar). In addition, through joint action with the federal authorities and the State of Mexico, three Air
Quality Improvement Programmes for the ZMVM (PROAIRE initiatives) have been issued, introducing
measures to reduce emissions from a range of sectors. The latest programme, PROAIRE 2011-2020,
covers eight areas. Strategy 4 addresses mobility, focusing on the systematic planning of transport
networks, integration of the transport systems of Mexico City and the State of Mexico and improving the

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fluidity of traffic flows. Specific measures promote integrated planning with an emphasis on intermodal
journeys, traffic monitoring and management, additional express lanes for public transport, promotion of
cycling and rationalisation of freight distribution (Government for the State of Mexico et al., 2016).
Table 2.3. Current vehicle emissions regulations and competent authorities

Vehicles in circulation

New vehicles

Vehicle type

Regulator

Light duty(cars, SUVs)

SEMARNAT

Heavy duty
freight andpassenger

SEMARNAT

Heavy andlight duty in
Mexico City,
Hidalgo, Stateof Mexico,Morelos,
Puebla, andTlaxcalastates.
Light duty(cars, SUVs)
for the rest of
the country

Heavy duty
(freight andpassenger
transport)

SEMARNATSEMARNATSEMARNAT

Current regulations
NOM-042-SEMARNAT-2003
Limits equivalent to those from Tier 1
and 2 USEPA standards, and Euro 3 and
4 (2006 models and on); should have an
On-board diagnostics system (OBD II
and EOBD)
NOM-044-SEMARNAT-2006
Limits equivalent to EPA 2004 and EuroIV (year-models from 2008 and on)
NOM-EM-SEMARNAT-167-2016
Valid until January 2017.
On-board diagnosis system (OBD)
check; ASM testing method for vehicles
without OBD system, method equivalent
to a BAR 90 for heavy gasolineoperating vehicles or those using otherfuels; opacity test for diesel-operating
vehicles, both heavy and light.

Enforced by

PROFEPA(document review)

PROFEPA(document review)
States or municipalities(depending on local
legislation) through Vehicle
Inspection and Maintenance
Programs
Federal Ministry ofCommunications andTransport (for heavy vehicles
with federal number plate)

NOM-041-SEMARNAT-2015
ASM testing method, equivalent to BAR
97; for vehicles that cannot be used on a
dynamometer, BAR 90 (static method) is
authorised. On-board diagnostics system
check.

States or municipalities(depending on local
legislations) through Vehicle
Inspection Programmes

NOM-045-SEMARNAT-2006
Opacity measurements

Vehicles registered withfederal number plates:
Ministry of Communications
and Transport
Vehicles registered with local
plates – state or municipal
authorities (depending on
local legislations)

Source: Own elaboration with information from Transportpolicy.net

Mandatory vehicle inspection programme and No-Driving Day system
Mandatory vehicle inspection
In the ZMVM the mandatory vehicle inspection programme (PVVO) and No-Driving Day (HNC)
programs are linked: the result of the emission inspection procedures determines the way in which avehicle has to comply with the provisions of the HNC system. The last digit of the vehicle’s number
plate determines the color-coded category of the HNC system to which the vehicle belongs. This
determines the month in which inspections should be carried out (twice per year) and the day of the week
on which use of the vehicle is prohibited, when a restriction is applicable.

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Until 2015, every inspection program outside Mexico City was based on a static test (equivalent to a
US Bureau of Automotive Repair test using 1990 criteria – BAR 90 test). That year, SEMARNAT issued
the NOM-041-2015 regulation, requiring all States to use an Acceleration Simulation Mode (ASM)
dynamic test (equivalent to a BAR 97 test), which was already in use in Mexico City since themid-1990s, to measure NOx emissions from all vehicles in use in Mexico. The static test method can
now only be used as an exception and States have until 2018 to complete updating of test equipment andprocedures.
In the central area of the country, the States of Mexico, Hidalgo, Morelos, Puebla and Tlaxcala havealigned their programs with that of Mexico City in order to avoid restrictions on vehicles entering
Mexico City or the municipalities of the State of Mexico that are within the ZMVM for non-compliancewith the HNC system. However, few cities in other states have a Mandatory Vehicle Inspection
Programme (PVVO). In 2012, only 21 cities had inspection programs and many of these were notmandatory (SEMARNAT, 2012). Their scope and the level of compliance are difficult to determine.
Vehicles circulating in Mexico City but registered in these cities or cities that do not have a mandatory
inspection programme are likely to have higher emissions on average than those registered in the
ZMVM, with a negative impact on the air quality of Mexico City. The use of these vehicles is also
therefore restricted once they enter Mexico City or municipalities of the State of Mexico within the
ZMVM.
The vehicle inspection programme in Valle de México is the oldest and most mature in the country.
It came into effect in 1989 and has been adjusted to adapt to changes in the vehicle fleet and conditionsin the city. In 2010, the Mario Molina Center carried out a comprehensive assessment and found that thecompliance level for this programme was close to 80%, with most vehicle owners undergoingverification procedures in due time, as required by local regulations (Centro Mario Molina, 2010).
Measurements carried out with remote sensing devices9 in cities across the country show that theemissions from the vehicle fleet circulating in the ZMVM are lower than those in cities with inspection
procedures that use static tests or where there is no inspection programme at all (Figure 2.10).
The inspection tests applicable to different generations of light-duty vehicles are summarised inBox 2.4, with the currently applicable tests and emissions limits. Heavy-duty vehicles are also subject toinspection. Vehicles that pass the tests are awarded corresponding certificates and windscreen stickers
classified from 00 (cleanest vehicles) to 2. Vehicles that fail inspection can undergo repairs and retesting
and may qualify for retrofits of three-way catalysts.

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Box 2.4. Mandatory inspection and maintenance tests (NOM-EM-167-SEMARNAT-2016 standards)
1.

New vehicles:a) Mandatory check of On-board diagnostics system on the following five points:i.
Inappropriate Cylinder Combustion Conditions detection system
ii.
Catalytic Converter Efficiency systemiii.
Fuel System
iv.
Oxygen Sensor Systemv.
Comprehensive Component System.
Every monitoring point has to be functional and must present no failures.
b) If this condition is complied with, the vehicle is granted a Double-Zero (00) sticker as well as an
exemption from inspection for up to two years, renewable for another two years.

2.

Vehicles equipped with a three-way catalytic converter and a second-generation On-board diagnostic
system (OBDII or EOBD) (model-year 2006 on, according to regulation NOM-042 for new vehicles):a) Check of the On-board diagnostic system on the mandatory five points
Measurement of emission levels through dynamic testing. Emissions should not exceed thefollowing limits:
Maximum allowable limits for gasoline vehicles
Test

HC (ppm)

CO (%vol)NOX (ppm)

Dynamic

80

0.4

250

Static

100

0.5

NA

CO+CO2 (%vol)
Min

Max

13

16.5

O2 (%vol)(lambda)

0.4

1.03

2

1.03

b) Vehicles that comply with both conditions can obtain a zero (0) holographic sticker. If not, they canbe granted a one (1) holographic sticker or rejection, according to their emissions test results.
3.

Vehicles with electronic injection systems (model-year 1994 to about 2005):a) Visual smoke detection check-up carried out at 24 km/hb) Emission level measurements carried out through dynamic tests should not exceed the following
limits:Maximum allowable limits for gasoline vehicles
Test

HC (ppm)

CO (%vol)NOX (ppm)

Dynamic

100

0.7

700

Static

100

0.5

NA

CO+CO2 (%vol)
Min

Max

13

16.5

O2 (%vol)(lambda)

2

1.03

2

1.03

c) Vehicles that comply with both criteria can be granted a one (1) holographic sticker. If not, they canbe granted a two (2) holographic sticker or rejected, according to their emissions test results.
4.

Vehicles with mechanical injection systems (model-year 1993 and earlier, approximately)a) Emission level measurements through static or dynamic tests should not exceed the following limits:
Maximum allowable limits for gasoline vehicles with mechanical injection system
Test

b)

HC (ppm)

CO (%vol)NOX (ppm)

Dynamic

350

2.5

2000

Static

4000

3.0

NA

CO+CO2 (%vol)
Min

Max

13

16.5

O2 (%vol)(lambda)

2

1.05

2

1.05

Vehicles that comply with both criteria can be granted a two (2) holographic sticker or rejected,
according to their emissions test results.

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Figure 2.10. Comparison of nitrogen monoxide (NO) emissions from vehicles in use in States with andwithout an inspection and maintenance programme
25

gr NO/kg fuel

20
15
10
5
0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

No IM

Antiquity (Years)
Static IM

D.F.

Note: “No IM” = cities with no PVVO; “Static IM” = cities that enforce programs based on static tests; “DF”= Mexico City andits metropolitan area.
Source: Eastern Research Group, Inc., (2016).

The inspection program was modified in 2015 and again in 2016. As already noted, legal challenges
to including vehicle age in the conditions for awarding I&M certification were upheld by the Supreme
Court in 2015. The system was therefore modified to award certificates purely on the basis of test result,which resulted in an estimated 1.3 million vehicles being reclassified from class 1 to class 0 (thereby
escaping restrictions on circulation). The programme was modified again for conformity with theemissions limits established by the emergency regulation, NOM-EM-167-SEMARNAT-2016, issued by
the Federal Environment Ministry on 2 June 2016 in response to the episodes of high ozone
concentration that occurred between February and May in the ZMVM. This regulation is applicable for
Mexico City, as well as the States of Mexico, Hidalgo, Morelos, Puebla and Tlaxcala, coming into effecton 1 July 2016 and renewed for a further six months in January 2017 with a view to nationwide
application thereafter.
The 2016 regulation established a number of additional tests depending on the vehicle’s emission
control technology. The new standard focused on reducing NOx emissions in particular, reducing limits
for vehicles from 2006 model year on from 500 to 250 ppm; for vehicles from the 1994 model year
onwards from 1 500 to 700 ppm and for older vehicles from 2 500 to 2 000 ppm (see Box 2.4). As can beseen in Figure 2.11, the number of vehicles in the 1 category had collapsed as a result of the 2015 ruling,with more than three quarters of vehicles classified 0 in the first half of 2016. The new regulation has
reduced 0 certification to 47% of vehicles tested with 23% in class 1. The CAMe estimates that overall
1.9 million vehicles will lose 0 certification as a result of the change.
Vehicle inspection programs in the CAMe States are currently undergoing modification to make useof OBD inspection across the region, in alignment with procedures in Mexico City. The new tests will befully operational in mid-2017. At the same time, a failure of vehicle manufacturers and distributors tocomply with legal requirements to equip vehicles with second generation OBD systems since the 2006
model year has resulted in major problems for OBD-based inspection. In the second half of 2016 (to5 December) 111 000 vehicles were rejected by I&M centres in Mexico City because of inoperable OBD
or monitoring disabled by the manufacturer (see Table 2.4). The demand for retesting caused congestionin the processing system and delays. Adjustments were made to the process to reduce the need forretesting in October but legal action to enforce the regulation requiring second generation OBD on new
vehicles is clearly indicated.

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Figure 2.11. Classification of vehicles under I&M testing in 2016

1

st

2

nd

3%

4%

75%

47%

6%

23%

2%

2%

14%

24%

Source: Adapted from SEDEMA data.

Table 2.4. Causes of rejection under I&M testing in Mexico City 1 July to 5 December 2016
Cause of rejection

Number of vehicles

Share

Excess emissions

182 756

42%

Inoperable OBD or disabled monitoring

110 937

26%

OBD faults

79 92818%

Other causes

62 621

14%

Source: SEDEMA.

Figure 2.12. Classification of vehicles under I&M testing in 2nd half of 2016 by vehicle cohort
90000080000070000060000000

50000004000001300000

73%

23%

4%

2
Fail

2000001000000
2006-2017

1995-2005

1994 and older

Source: Adapted from SEDEMA data.

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No-Driving Day system
The No-Driving Day (HNC) system was introduced in Mexico City in the last quarter of 1989, in
response to persistent high concentrations of atmospheric pollutants, prohibiting the use of vehicles one
day a week and applicable to all vehicles regardless of emissions control technology or age, and set
according to the last digit of the vehicle’s number plate. Like the other programmes described, it has
undergone modifications according to the results and recommendations of technical studies. Currently,
the HNC system restricts vehicle use according to the category awarded (00, 0, 1 or 2) under the periodic
mandatory inspection programme. This is indicated by a holographic windscreen sticker. This and thecolour of the sticker, which is based on the last digit of the number plate determines on which days of theweek use is prohibited. Table 1.7, taken from SEDEMA’s website shows the vehicle use restrictions that
apply according to holographic windscreen sticker and number plate. Double zero and zero stickers
exempt vehicles from restriction.
The holographic windscreen sticker awarded depends on the vehicle’s emissions control technology
and the results of the tests carried out under the mandatory inspection and maintenance program, as set
out in Box 2.5 (SEDEMA, 2016b). A check on catalytic converter operation is also carried out; if its
efficiency has undergone a considerable decrease the vehicle is subject to a converter replacement
procedure under the Comprehensive Pollutant Emission Reduction Program (Programa Integral de
Reducción de Emisiones Contaminantes) (PIREC).10
Certification and windscreen sticker categories are currently awarded as shown in Table 2.5 forvehicles that comply with the inspection and maintenance tests. The system was last updated in 2016
when, significantly, no-fault OBD test compliance was introduced for all diesel vehicles eligible for
0 certification. This was done to align requirements with the emergency regulation issued by the Ministryof Environment for the ZMVM in April 2016 in response to elevated ozone levels (NOM-167).
Table 2.5. Summary of vehicle categorisation under emissions testing
ExemptElectric and hybrid vehicles.

00

New vehicles for individual use under 3.857 tonnes using gasoline or natural gas.
New vehicles over 3.857 tonnes using diesel that meet Euro VI / EPA 2010 emissions standards and areequipped with particle filters (heavy vehicles using gasoline are not eligible for 00 certification).

0

Vehicles using gasoline, natural gas, LPG and alternative fuels equipped with a three-way catalytic
converter and second generation OBD (effectively 2006 models and more recent cars).
Diesel vehicles from model year 2008 that pass a smoke test (1.0m-1 light absorption) and present no
OBD faults.

1

Vehicles using gasoline, natural gas, LPG and alternative fuels with electronic injection.
Diesel vehicles that pass a smoke test (1.2m-1 light absorption).

2

Vehicles using gasoline, natural gas, LPG and alternative fuels with mechanical injection.
Diesel vehicles under 3.857 tonnes that pass a smoke test (2003 models and older 2.0m-1, 2004 models
1.5m-1)
Diesel vehicles over 3.857 tonnes that pass a smoke test (1990 models and older 2.25m -1, 1991 models
1.5m-1)

Source: Ciudad de Mexico (2016).

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Figure 2.13. Windscreen sticker (left) and No-Driving Day information display on
the Aire mobile phone application (right).

Compliance with the emission limits as well as with the On-board diagnostic system check is madethrough authorised Vehicle Inspection Centres. Additionally, measurements are carried out on the streetswith remote sensing equipment, on visibly polluting vehicles. Penalties for not complying with the
PVVO are significant. Vehicle owners that present their cars late receive a penalty and, in case they aredetected by a traffic officer, their vehicle can be detained or confiscated; in addition, the vehicle ownermust pay the corresponding fine. Vehicles that do not comply with vehicle inspection requirements canrepeat the inspection after repair, but if they fail to comply with the established dates, they are
sanctioned.
Vehicles from other states can undergo inspection procedures voluntarily under the Mexico City
scheme and be granted their corresponding windscreen stickers, according to their technology andemissions. This is not a requirement, but verification procedures make it possible for them to circulate
every day, according to the No-Driving Day provisions.
The HNC system is applicable across all of Mexico City, as well as in the 18 municipalities of theState of Mexico included in the HNC system.11 The traffic authorities are in charge of supervising thecompliance of this program. In case of non-compliance, vehicles are withdrawn from circulation and sent
to a vehicle pound. In order to retrieve them, the owner must pay the corresponding fine, and if violation
took place on an environmental alert day, they must wait to retrieve their vehicle until the alert is over(Mexico City Government, 2014).
Vehicles with plates that come from states that do not have an agreement with Mexico City and thathave not been subject to voluntary inspection in Mexico City cannot be driven in the City Monday
through Friday from 5:00 to 11:00 or on Saturdays from 5:00 to 22:00 and, according to the last number
on their plates, one day of the week, from 5:00 to 22:00 hours. Circulation restrictions are stricter whenthe Atmospheric Environmental Alert Program is activated.
Although it has been observed that the HNC system has encouraged households to purchaseadditional vehicles to escape restrictions and thus increased the number of vehicles circulating in the city,
the vehicle fleet in Mexico City is cleaner and more modern than that in the rest of the country (as shownin Figure 2.10). This program, along with the PVVO, has probably resulted in an accelerated renewal ofthe vehicle fleet (due to the advantages accorded the most recent vehicles). This is consistent with a

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study of the vehicle restriction program for Santiago de Chile, where they found that due to exemptions
being granted to vehicles with advanced emission controls, the program had encouraged vehicle fleet
renewal (Barahona et al., 2016).
Atmospheric Environment Alert Program (PCAA)
This program includes a series of measures to cope with episodes of high concentrations of ozone orparticulate matter (PM10) recorded by the Environmental Monitoring System (SIMAT). These measures
are applicable within the 16 territorial delegations of Mexico City as well as 18 municipalities of theState of Mexico included in the HNC system. Until April 2016, this program included three stages:
pre-alert, Stage I Alert and Stage II Alert. The pre-alert stage was activated when pollutant
concentrations reached 150 IMECA points. The programme was established in 1988; since then, its
activation thresholds and response measures have undergone modification. From June 2008 on, limits forboth pre-alert and alert phases were lowered, and in April 2016 the pre-alert stage was eliminatedaltogether and in December 2016, air quality forecast was introduced as part of the programme(SEDEMA, 2016c).
The alert program includes measures to reduce exposure to pollution (for instance restriction of
outdoor activities), restrictions on the use of some vehicles and measures to reduce emissions from othersources. These include controlling PM10 and ozone precursor emissions in the service sector (roadsurfacing and repair, wood combustion, and a 20% reduction in the distribution of liquefied petroleum
gas for vehicle refuelling) and in the industry sector (aiming at a reduction of 30-40% of particulate andozone precursor emissions by restricting the activity of un-controlled fixed emissions sources ).
Table 2.6. Mobility restrictions during environmental alerts

Alert
level

Stage I

Stage II

Activation
points(Air Quality
Index)
Ozone PM10

Mobility restrictions

Over 150- Vehicles with class 1 holographic windscreen stickers restricted onalternate days according to the last digit of their number plate, odd oreven. Vehicles with class 2 holographic windscreen stickers are
restricted on all days during the alert.
(Class 0 and 00 vehicles are exempt from restrictions but wererestricted on alternate days during the alerts between April and July2016).
- Freight transportation (federal or local plates) prohibited between
06:00 and 10:00.
Trucks carrying perishable products restricted to operate between
22:00 and 05:00 in Mexico City

Over 200- Every vehicle with a 1 or 2 holographic windscreen sticker
prohibited. (Type 0 and 00 exempt).
-Freight vehicles restricted on alternated days according to the last
number on their plate (local plates) and third number (federal plates).

Source: SEDEMA (2016c).

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Alertsuspension
pointsEqual orless than
150 and air
qualityforecast

78 – 2. AIR POLLUTION AND MITIGATION MEASURES IN MEXICO CITY TODAYThe SIMAT records concentrations and alerts for the CAMe, which in turn issues alerts. From themoment an alert it is declared, environmental pollutant concentrations are continuously evaluated with
reports issued to the public at 10:00, 15:00 and 20:00.
Currently, Environmental Alerts are declared within the hour following the recording of ozone andparticulate concentrations at any SIMAT monitoring station that generates the Air Quality Index
activation point levels indicated in Table 2.6. Emergency service vehicles, transport for disabled people,
school buses, refrigerated trucks, concrete mixers, funeral vehicles and motorcycles are not subject tothese restrictions. In the case of particulate matter alerts, a regional alert is declared if high concentration
values are only recorded by the monitoring station in the area, and an alert for the entire metropolitan
area declared if there are two or more zones recording high levels, this determines the territorial extent
for application of restrictions.
Other emissions control measures
Several additional pollution mitigation measures in the transport sector have been introduced asfollows (SEDEMA, 2016d):
Voluntary diesel vehicles programme (Programa de autoregulación): This program is designed
for freight and public transport. Under the programme, owners of these vehicles agree toundertake preventive maintenance and measure vehicle emissions (on a bi-annual basis for
freight and on a quarterly basis for public transport) in exchange for an exemption from the
HNC program. The self-regulation program also comprises a vehicle renewal program in orderto replace existing units with cleaner, more efficient vehicles, such as EURO VI and EPA 2010
compliant trucks, or retrofit emission control systems (oxidation catalysts and particle filters).
In November 2016 there were 9 235 vehicles registered under this program, belonging to
30 own-account operators and 13 passenger transport companies.



Retrofit program for buses: Since April 2015, pilot tests have been carried out for the
installation of particle filters on vehicles. Filter installation is programmed for 540 public buses
and school busses, aiming to achieve an estimated reduction of 8 tonnes/year of PM10 and
7 tonnes/year of PM2.5. In May 2016, the Official Gazette published the call for tender for"Authorization as a distributor of oxidation catalysts and diesel particulate filters for vehicles
circulating in Mexico City". Four authorisations had been issued for particle filters as of May
2017 and one for oxidation catalysts; the call is still open.

Comprehensive Pollutant Emission Reduction Program (Programa Integral de Reducción deEmisiones Contaminantes - PIREC): Under this program a pilot in the second half of 2014provided for free replacement of catalytic converters for light-duty vehicles that are over
15 years old, and replacement of catalytic converters on more recent vehicles where failures
were detected during vehicle inspection tests. In 2014, at no charge, 30 221 converters were
installed on light-duty vehicles that were older than 15 years and in the last two years
14 703 catalytic converters were fitted on vehicles rejected in emissions testing through sevencompanies at 126 workshops. In March 2016 a call for authorised distributors of catalytic
converters for vehicles with second generation on-board diagnostic systems (OBDII) was
published in the Official Gazette, in order that replacement converters are available for vehicles
that present faults in their emissions control devices. Catalytic converters reduce NOx, CO andHC emissions more than 70%.

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School transportation program: This program establishes that elementary and junior highschools with over 490 students should implement a mandatory collective school transport
program for all their students, making an exception for those who arrive walking or on bicycle,
those who have any disabilities, those who are not covered by established bus transport routes
or whose families work on campus. This program initiated in2009 in schools with over
1 240 students and, since 2011, is being implemented in schools with over 670 students,
progressively incorporating more schools. Currently, 63 schools participate in this program.

Results of the measures
Currently, Mexico City has about 66 inspection centres with 340 vehicle verification lines. Eachsemester about 1.8 to 2 million units are tested. Reports issued by SEDEMA indicate that models 2006
and on are mostly granted a type 0 windscreen sticker, while 1994-2005 models are granted
type 1 windscreen stickers and 1993 or older get a type Two sticker (SEDEMA, 2016c).
The Ministry of Environment of Mexico City grants authorisations to operate inspection centres anddetermines maximum prices for inspection. The last tender for inspection centres was published on
3 July 1996, from which 71 Vehicle Inspection Centres are still in existence and operating. These havesince renewed their authorisations, but these will all expire on 31 December 2017.
For the last semester (1 July to 5 December 2016), the rejection rate was 23%, with over
436 000 vehicles. For the most part (65%, 284 300) of these were model-year 2006 and on, despite
having three-way catalytic converters and On-board diagnostic systems as required by the Mexican
regulation. The most frequent rejection cause was non-compliance with the limits, followed by rejections
due to the fact that the On-board diagnostic system was not enabled by the manufacturer, or a failure on
the unit connector that impairs communication with the on-board computer system (SEDEMA, 2016c).
This is, to a great extent, attributable to inadequate maintenance.
Even though the most recent vehicles (year 2016 and 2017 models) should be able to obtain a
Double-Zero type windscreen sticker, statistics from the second semester of 2016 show that over 20% of
these vehicles did not obtain their two-year verification exemptions; 8% were rejected, 13% were granteda type Zero windscreen sticker (due to emissions exceeding the limits for 00 stickers) and 2% were
granted a type One holographic sticker for the same reason. The top ten manufacturers with a highpercentage of new vehicles that were unable to obtain type Double-Zero stickers were: Renault (Kangoo
94%, Fluence 94%), Fiat (Palio, 79%), Chrysler (Vision, 79%), Toyota (Yaris, 73%), Ford (Lobo, 67%),
Ram (700 Club Cab, 66%), Toyota (Corolla, 64%), Ram 700 (60%). The main cause of rejection in mostcases was connection errors or “non-completed” monitoring. However, SEDEMA has detected brands
that have recurring issues with their Cylinder Connection Inadequate Situation Detection systems(SDCIIC), or with their fuel system monitor (SC), or with their integrated component system (SEDEMA,
2016c).
Table 2.7. Emissions testing pass and fail rates, Mexico City 2016

Number plate

5+6

7+8

3+4

1+2

9+0

TOTAL

Approved

317 314302 535

290 049294 424

296 680

1 501 002

Missing

49 17156 69458 83056 65957 353278 707

Missing %Source: SEDEMA.

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80 – 2. AIR POLLUTION AND MITIGATION MEASURES IN MEXICO CITY TODAY

It is important to mention that the measures to regulate emissions have become stricter in Mexico
City. This has reduced the vehicle fleet registered in the city, since automobile owners have changed theregistration and plates of their vehicles to those from other States where regulations are lax. Work forhomogenising regulations is currently taking place.
Table 2.8 shows the number of vehicles that were approved through the vehicle inspection
programme during the second semester of 2016, categorised according to the last digit of their plate, andwhich in turn defines the colour assigned. The table also shows vehicles that were not processed in thevehicle inspection programme during the second semester but did go through testing during the firstsemester of the year.
The vehicle fleet inspected during the second semester included about 300 thousand vehicles fromeach colour code. This includes vehicles with holograms “00”, “0”, “1” and “2. About 50 000 vehicles
from each group did not go back to the programme in the second semester. A similar deficit wasobserved in roadside testing with a remote sensing device in the ZMVM. Figure 2.15 shows the place ofregistration of the vehicles tested; Figure 2.14 summarises the results of emissions testing.
Figure 2.14. Vehicles tested on the road with a remote testing device in the ZMVM in 2015 and 2014

Federal648
2%State of
Mexico13 59539%

Metropolitan
324
1%

Other
562
2%

2014

Federal Other
527 1 569
2%
1%

State of
Mexico35 42651%

Mexico City
(CDMX)
19 30656%

2015

Mexico City
(CDMX)
32 49746%

Source: SEDEMA.

From Figure 2.15, the following can be observed:


Vehicles registered in the State of Mexico show higher emission concentration levels thanthose registered in Mexico City for the three criteria pollutants. The sample for each state is ofabout 18 000 vehicles.

Vehicles with the highest CO concentrations were those registered in Michoacán, Tlaxcala andGuanajuato; those with the lowest concentrations were those registered in Morelos, Puebla andJalisco.



The highest HC concentration level was shown by vehicles registered in Michoacán while thelowest concentrations were shown by vehicles in Morelos, Jalisco and Nuevo León.



In the case of NOx emissions, the highest concentration was also shown by vehicles registeredin Michoacán, while the lowest by vehicles from Morelos and Guanajuato.

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Figure 2.15. Exhaust gas emissions concentrations for vehicles tested in the field in the ZMVM by place ofregistration (Median values for the month of testing)CO (% volume)

HC (ppm)

0.35
0.3
0.25
0.2
0.15
0.1
0.05
0

256
128
64
32
16
8
4
2
1

NOX (ppm)
512
256
128
64
32
16
8
4
2
1

Source: SEDEMA.

Low emission zones
Recently, some cities within the Megalopolis12 have started designing and developing pilot
programs in order to implement low emission zones (LEZ). LEZs are fairly common in European cities.
Although there is not an exact definition, since their design has some variation by city, these zones are
generally geographic areas within which a certain type of motor vehicle has restricted access.
Commonly, these are the most polluting vehicles. It should be noted that the effectiveness of an LEZ
depends mostly on the appropriate definition of at least the following three characteristics:
1. Type of vehicle use restriction: Generally LEZs impose a complete prohibition for those vehicles
that fail to comply with required specifications. However, some schemes allow access in
exchange for a significant payment.13 In addition, it is necessary to define days, schedules, air
quality limits and extraordinary situations, such as peak pollution episodes, that would beapplicable to the LEZ.

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2. Regulated vehicles: Since the regulation can be applicable to combinations of passenger andfreight vehicles, diesel and/or gasoline vehicles, etc., it is of the utmost importance to analyse
whether the application to any particular sector would have a greater impact, if its
implementation would be made easier, or if there are any elements on the current regulation
framework that could have an effect (positive or negative) on the effectiveness of the LEZ.
3. Geographic area: The main European cities where these zones have been established havedefined fairly extended areas. Since their goal is to reduce population exposure to pollutants, thesize of the LEZ should be one that guarantees minimum pollutant dispersion within it but also
encourages an accelerated vehicle fleet renewal, thus extending the effects of this program tozones outside it.
Cities such as Cuernavaca and Toluca have extended the concept of the LEZ and are working on theimplementation of eco-zones. Inspired by the LEZ, these zones aspire not only to reduce pollutant
emissions, but also to improve urban spaces, promote non-motorised mobility, reduce road accident rates
and encourage economic activities within the area. Table 2.8 presents the definition, objectives and therelation with air quality of the proposals in Cuernavaca and Toluca.
Table 2.8. General description for Cuernavaca and Toluca eco-zones
Cuernavaca

Toluca2

Coverage area
Specific definition andeco-zone objective, as
defined by the city

1.8 km , centre of the city
The eco-zone is an area of intense
urban activity. The goal is toimplement actions in order to reduce
polluting emissions and recoverenvironmental value areas.

Implementation
details

There are currently no specificprograms; the city is still analysing
applicable alternatives.

Air quality specificdetails

According to their preliminary plan,
one of the main goals within the ecozone is to reduce those pollutants the
population is exposed to, thus
mitigating negative health effects.

2.6 km2, centre of the city
The eco-zone is an environmental priority area;
its goal is to improve living quality for its
inhabitants and residents through theimplementation of comprehensive actions that
reduce pollution, improve public spaces andpromote sustainable mobility.
Eco-zone programs are divided into sevencategories: public lighting energetic efficiency,
solid waste management, public spaces, urban
development, environmental education,
pollution and smart mobility.
The current plan does not contemplate any
action related to internal combustion vehicles,
except for parking control on the smart mobility
program.

Undoubtedly, eco-zones could be an important tool for urban economic and environmental
management. However, the pursuit of numerous objectives through a single tool demands additional
efforts in order to guarantee that the necessary elements for achieving each objective are effectively
included in the regulatory design.
Without undermining the other goals pursued by the eco-zones, Mexico City would benefit most if
they first design an LEZ to improve air quality. This would not prevent additional mechanisms being
included gradually in the LEZ over time. One advantage of concentrating on air quality resides in theinternational experience available in the design of an effective instrument. Table 2.9 shows basic design
elements for some of the European LEZ.14

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Table 2.9. Low emission zone basic characteristics in European cities

Stockholm

LondonMilan

BerlinImplementation
year
Regulated vehicles

1996

2008

2011

2008

Trucks and buseswith a weight over
3.5 tonnes and overeight years old

Trucks, buses andpassenger cars

Trucks, buses andpassenger cars

Fuel

Diesel only

Trucks with a grossweight over 3.5 tonnes.
Buses with a grossweight over 5 tonnes.
Vans and pick-ups
based on their grossweight and antiquity
Diesel onlyDiesel and gasoline

Low emission zone
dimensions
Operative hours

30 km2~1 000 km2

Diesel andgasoline~1 100 km2

Permanently, allyear round

Permanently, all year
round

Permanently, all year
round

Optional fees*

Not allowed

Fines*USD 120

Between USD 85
and 513

USD 90

Verification

Monitoring carriedout by the police,based on thevehicle’s certificates

Allowed
Between USD 140 and
240 a dayUSD 360-1 440(50% reduction if it ispaid within the first 14
days)
Electronic system withplate recognition
camerasDifferentiateddaily schedule.
Variations
according to themonth of the year
Not allowed

Monitoring
carried out by thepolice, based on
the vehicle’s
certificates

Monitoring carriedout by the police,based on the color of
their windscreen
sticker

88 km2

Not allowed*Fees and fine amounts correspond to information from April 2016. Local conversion to USD is based on the average exchange
rate for the same month.
Sources: General characteristics of European regulations, available at: http://urbanaccessregulations.eu/

The cases of Stockholm, London, Milan and Berlin and other cities show that despite theirdifferences, two common elements can be identified and should be taken into consideration if case
Mexico City aspires to implement a LEZ:
1. The surface of the LEZ must be proportionate, regardless of its absolute size, and sufficient inextent compared to the total area of the city if it is to be effective. Size varies from about 30 km2
for Stockholm to 1 000 km2 for London.
2. Restriction of access for heavy diesel vehicles - trucks and buses - is common to every LEZ.
Some eco-zones regulate light-duty gasoline vehicles as well, but the greatest focus is on
heavy-diesel vehicles.
Accordingly, an LEZ that focuses on heavy-diesel vehicles in Mexico City could be an effective
tool for local pollutant reduction. Those diesel vehicles are responsible for over 90% of particulate matter(PM2.5) emissions from traffic in Mexico City and for about 50% of nitrogen oxide (NOX) emissions(SEDEMA, 2016a).

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It is suggested that the implementation strategy considers a range of actions for both the short andlong term. Figure 2.16 shows these elements graphically. As a central short term action, theestablishment of a regulatory provision for an LEZ for heavy vehicles operating on diesel is the maingoal. Taking that as a starting point, parallel actions are developed, including the definition of the area tobe covered, schedules, monitoring and surveillance systems.
It is important to observe that in the medium term, the inclusion of light-duty vehicles and ofadditional programmes within the LEZ can be considered. However, in order to avoid hindering theregulation process and thus deferring benefits from emission reduction including the immediate healthimpact, it is suggested that actions that have proved to produce results in other cities have the highest
priority. Finally, it is important to carry out an assessment of the relevance and feasibility of linking
Mexico City’s LEZ with other programmes that have already been established and could enable theimplementation of the LEZ and create synergies.
Figure 2.16. Low emission zone implementation framework

Programmes focused on the freight sector that will be the main subject for this analysis include thefollowing initiatives (German Cooperative for Development et al., 2015):
1. Clean Transportation Program: This is a voluntary program from SEMARNAT that has the
purpose of making freight and passenger transport more efficient, through the adoption ofstrategies, technologies and better practices. Transport companies as well as users of freighttransport record actions taken in order to reduce their emissions as well as their fuelconsumption, in exchange for consultations, training and, occasionally, financing for theincorporation of new technologies.
2. Vehicle Substitution Scheme: This programme operates under the Decree for the Substitution
and Vehicle Renewal Scheme (Decreto para el Esquema de Sustitución y Renovación Vehicular)
issued on the Official Gazette on 30 October 2003 (Decree), by which a fiscal incentive isgranted to the contributor (heavy vehicle assembly plants and distributors) taking as a reference
the compared value of the destroyed unit against the value of a semi-new or new unit to bepurchased.

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3. Federal Auto-Transportation Fleet Modernisation Program: Operated by Nacional
Financiera (NAFIN), its goal is to enable the renewal of the freight and passenger federaltransport fleet on a national level. Through this mechanism, transport companies can accessfinancing in order to purchase semi-new and new trucks of less than six years. In order toincrease credit granting and thus enabling more unit renewal, the Federal Government offers
counter-guarantees to the interested financial intermediaries.

Outline of other policies considered for development of a new strategy to reduce air
pollution
Following the episodes of high pollutant concentrations in the first semester of 2016, several
institutions developed documents with recommendations for additional measures to reduce ozone
concentrations in the ZMVM and avoid these episodes. The Autonomous National University of Mexico(UNAM) presented a series of suggestions through a press release, synthesised as follows (Dirección
General de Comunicación Social de la UNAM, 2016):


Implement a selective control for those sources that emit volatile organic compounds (VOCs)
that promote ozone formation, instead of indiscriminately reducing vehicle emissions.



Include those industries or services that make profuse use of organic solvents, such as furniture
manufacture, metal-working and car painting repair.



Broaden the application of the emissions controls programmes to the 42 municipalities from theState of Mexico that are not currently included but are part of the same atmospheric zone that
Mexico City belongs to. Accordingly, impose a control system for fugitive VOC emissions
from petrol fumes at gas stations in these municipalities.



Promote safe, high quality public transport in order to avoid additional vehicle acquisition.

Demand that vehicle manufacturers comply with stricter emission standards. Mexican Federal
Government should guarantee better quality for fuel supplies as well as verify vehicle and fuelregulation is complied with.

Strengthen and maintain monitoring networks and strengthen the capacity of federal agencies
that are part of the CAMe.

Fight corruption in verification centres.

In May 2016, the Mario Molina Center presented six priority strategic lines for reducing emissions(Centro Mario Molina, 2016):
1.

Accelerate the development of low emission public transport systems of high quality andintegrated at a metropolitan scale. Extend BRT mass transportation systems by at least 40 km
each year and integrate the systems of Mexico City and the State of Mexico in order toharmonise service quality and prices, focusing on surrounding municipalities in the State of
Mexico. Immediately initiate pending projects such as the subway network expansion, eight
Metrobus lines and five Mexibus lines.

2.

Promote more rational use of cars as well as clean technologies. Fix prices for fuel that reflect
their externalities, at rates that discourage car use, introduce congestion charges and introduce
parking space limitations and a tax or rent associated to the value of parking spaces and related
to the vehicle’s dimensions and emissions. Encourage a technological transformation fortransportation (with incentives for electric and hybrid vehicle acquisition, programmes for the
installation of particle traps on buses, accelerate catalytic converter replacements).

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3.

Drastically reduce freight emissions. Update the NOM-044 regulation for new vehicles as well
as extending the parameters and procedures of NOM-045 for vehicles in use; guarantee astrategic supply of ultra-low sulphur diesel on priority corridors; establish schedules and routes
for access and circulation of freight within the ZMVM; generate incentives in order tostrengthen vehicle scrapping programmes for obsolete, heavy vehicles and limit the entrance ofvehicles from outside ZMVM.

4.

Update regulations on vehicle inspection to guarantee compliance.

5.

Reduce pollutant emissions that come from industrial activities as well as fuel distribution; andprevent and avoid fires. Update emission regulations for specific sources; assess the closure or
relocation of industrial sources that affect high population density areas; generateenvironmental auditing emergency programmes that focus on reducing VOCs, NOx andparticulate matter; control liquefied petrol gas as well as natural gas leakages, control vapour
fumes generated by diesel and gasoline in service stations; control forest fires.

6.

Contain the expansion of the urban area in order to reduce mobility demand. Develop a
Territorial Regulation Program on the megalopolis scale and update the Urban Development
General Program for the city, focusing on mixed land use and consolidation aroundpoly-centres, in order to de-concentrate activities and travel.

The CAMe and its technical consultants are currently analysing these and other measures in order toreduce the occurrence of critical atmospheric pollution episodes and improve Mexico City’s air quality inthe long and short term.

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3. Real-world vehicle emissions
The current state of affairs in Europe15
Real-world vehicle emissions differ from the legislative emissions limits for a number of reasons. In
most cases emissions, in grams per kilometre, are higher than the type-approval, or factory value. But
emissions can also be substantially lower. This section aims to outline the main reasons for the deviations
and the implications for managing air pollution. The European situation is taken as example.
In the past attention was directed mainly at the reduction of the emissions of heavy-duty vehicles.
However, the latest generation of Euro-VI diesel trucks are very clean. They typically perform better onroad than the type-approval limits. Basically, the average modern 30-tonne truck has a lower Nitrogen
Oxide (NOx) emission than an average modern diesel passenger car. Combined with the increased shareof diesel passenger cars in the total fleet attention has shifted to these diesel passenger cars and to lightcommercial vans. The separation between light-duty and heavy-duty emission legislation lies at
3.5 tonnes in Europe.
Only recently, with the influx of these Euro-VI diesel trucks from 2014 onwards, has the impact ofheavy-duty vehicles on the total NOx emissions declined. Trucks were responsible for more than half theNOx emissions in many traffic situations on urban roads, despite the small fraction of trucks among thevehicles, 5% or less. The selective catalytic reduction (SCR) emission after-treatment system, used since2007 on trucks, functioned only in circumstances similar to the European Transient Cycle (ETC) typeapproval test. The corresponding on-road circumstances are heavy-loaded driving on the motorway. In
urban conditions the SCR system remained too cold to function and the NOx emissions of Euro-V trucks
are typically threefold to fivefold higher than the regulated limit.
With Euro-VI legislation for heavy-duty engines, there are three important changes. First, the newengine test, the World Heavy-duty Transient Cycle (WHTC), uses a lower engine load more comparable
to on-road usage. Second, a cold start is included in the test protocol. Finally, and maybe most important
for the success of Euro-VI legislation, the in-service conformity (ISC) test is no longer an engine test in
the laboratory but an on-road test with the vehicle in normal use. The NOx emissions of the first Euro-VI
trucks were extremely low; in a number of cases close to the bounds of measurement uncertainty.
Moreover, with continued testing emissions remain, in general, low for Euro-VI trucks with aging of thefirst vehicles and with new engines coming onto the market.
There are minor concerns for high emissions in special urban use, such as refuse trucks andinner-city busses, which still operate mainly outside the in-service conformity test regime.

Robust emission control technologies
In the last thirty years there have been two emission control technologies that have changed thelandscape for vehicle emissions. These are the three-way catalyst for petrol cars, and the diesel
particulate filter for diesel vehicles. Around 1990 the three-way catalyst was introduced forspark-ignition vehicles, such as petrol cars. This decimated the emissions of hydrocarbons (HC), carbon
monoxide (CO) and nitrogen oxides (NOx) of these vehicles (emissions of particulates [PM] were alreadylow for petrol vehicles), and it left diesel vehicles as the main polluters from 1992 onwards. Apart fromcold starts, aging and some failures in engine control systems, especially prior to 2000, the emissions of

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88 – 3. REAL-WORLD VEHICLE EMISSIONS

petrol cars have been very low. A catalyst requires time and fuel to warm up. The cold-engine start yields
higher initial emissions before the catalyst is warm. For petrol cars these so-called cold-start emissions
dominate total emissions, in particular for HC emissions.
The diesel particulates filter (DPF) has been standard for diesel passenger cars since 2009 and fortrucks since 2014. The addition to the European regulations of a particulate number emission limit,
accompanied with a measurement procedure which can detect particulates accurately in the lower end of
the size range, ensured appropriate application of DPF technology. The change in particulate emissions
with the introduction of the filter has been dramatic. The particulate mass limit was reduced by a factorof five for diesel passenger cars between Euro-4 (2005) and Euro-5 (2009) standards but the real-world
emissions decreased by at least a factor of fifty. Prior to the widespread application of DPFs, the averagereal-world particulate emissions of diesel cars were somewhat higher than the limits. For vehicles with a
DPF the emissions are far below this limit. The actual values are often around 0.5 mg/km, close to themeasurement uncertainty, while the limit is 5 mg/km.

The type approval test as the standard for compliance
The type-approval test for light-duty vehicles is executed on the prototype of a new vehicle model,
and repeated occasionally in the conformity-of-production tests on new vehicles directly from thefactory. The type-approval test is a well-defined protocol, with limited power demand on the vehicle,
such that all vehicle models can undergo the same test. Hence the demand on the engine during thetype-approval test is only a fraction of the typically available engine power in a modern European
light-duty vehicle. If vehicles in use are taken from the road to undergo these tests, the emissions areusually slightly higher but the performance on the type-approval test is generally satisfactory.
Occasionally, high emissions from in-use vehicles on the type-approval test occur due to malfunctioningor poor maintenance of the vehicle.
Contrary to light-duty vehicles, the engine demand in the type-approval test of a heavy-duty vehicle
is on the high side of the engine demand profile for normal use of trucks. For heavy-duty vehicles thetype-approval emission test applies to the engine rather than the whole vehicle, and is based on the rated
power of the engine. With the general increase in engine power over the years, the engines have beentested with higher and higher engine loads, while the real-world engine load remained more constant, andunrelated to rated engine power.
Thus the type-approval test for light-duty vehicles is focuses on the weakest link, low-powered
vehicles, while the heavy-duty engines are tested on high engine loads matched to engine power. Bothtype-approval tests therefore cover only a particular part of the engine load spectrum observed inreal-world usage.

The two separate worlds of type-approval and on-road in-use testing for light-duty diesel
vehiclesIn the real world, emissions can be much higher than on the type-approval test. This is particularly
the case for light-duty diesel vehicles. Recently, the “dieselgate” scandal with modern vehicles switching
to a customised emissions control strategy during type-approval and conformity of production tests
caught everyone’s attention, but there has been a steady increase in the difference between the real-world
emissions of light-duty diesels and the type-approval limits for at least a decade. This increase coincides
with the increasing complexity of emission control strategies and the electronic sensor and control
systems of the vehicle. Engine control nowadays is related to gear selection, ambient temperature, fuelquality and so on. Within the full span of driving behaviour, vehicle payload and ambient conditions the

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3. REAL-WORLD VEHICLE EMISSIONS – 89

specific conditions of the type-approval test are a smaller and smaller subset, with an increasing numberof parametric dependencies. Optimising emissions control technology on this subset of operating
conditions leads to a larger and larger area where emission control is of limited effectiveness. Around theyear 2000, high emissions were typically only observed under hard acceleration. Nowadays,
temperatures below 20°C, high engine speeds, high engine loads, speeds above 120 km/h, use of runninglights can all result in cases where disproportional increases in vehicle emissions are observed.
In particular over recent decades, real-world NOx emissions from diesel vehicles have remained
high, at about 0.6 g/km, despite the emission limit changing from 0.97 g/km (combined NO x andhydrocarbons [HC]) for Euro 1 legislation in 1992 to 0.080 g/km (NOx alone) for Euro 6 standards in2014. Seemingly, the applied emission control technology, which performs excellently in thetype-approval tests, has limited effectiveness in any other circumstance than the type-approval test. NOxemissions from light-duty diesels are high in almost all normal conditions on the road and for all vehicle
models until 2016.
Very recently some well-performing vehicles have entered the market, with on-road emissions
approaching the type-approval limit of Euro-6.

Designed, or optimised, for the type-approval test
Given the precise protocol and the limited demands on engine power in the type-approval test, sometechnologies can be designed for the type-approval testing that are less suitable for other vehicle use
conditions, in particular for higher engine power and dynamic driving. For example, an after-treatment
system can be designed for a maximum exhaust gas flow or a maximal amount of pollutants that can be
reduced. If this maximum is related solely to values occurring on the type-approval test, the emissions
will increase substantially in the real world with higher flows resulting from harder accelerations andhigher payloads.
Also engine temperature management is a complex matter, where the optimal operation of anengine, including durability considerations, can be at odds with the emission control system. Most diesel
vehicles use exhaust gas recirculation (EGR) to limit the NO x emissions during combustion. The
combination of more inlet exhaust gas and less oxygen (fresh air) in the cylinder reduces the combustion
temperature and hence the production of NOx. The amount of recirculated exhaust gas depends on the
power demand, the inlet pressure and temperature and other factors which depend strongly on the precise
operating conditions. Therefore, the EGR rate is dynamically controlled, and in the case of high power
demand, it can be restricted. NOx emissions can increase easily by a factor of three or more when the
EGR rate is reduced. Such circumstances may not occur in the type-approval tests but can be common in
on-road situations. The particulars of EGR control strategies have been key to the high real-world NOx
emissions of Euro-5 diesel cars, sold in Europe between 2009 and 2015. The real-world emissions ofthese vehicles are on average four times higher than the type-approval limit.
Around 2010 a number of vehicles showed high NOx emission levels in independently executed
type-approval test carried out at a laboratory temperature of 15°C instead of the 20°C to 30°C windowprescribed in the type-approval procedure. The rest of the test protocol was identical but the emissions
were about three times higher than at 20°C. It was considered an improper emission control strategy tohave such a large increase for such limited variation outside the test protocol. On the other hand, there
was no implementing regulation which set a precise limit on the acceptable increase in emission whiledeviating outside the operation region of the type-approval protocol.

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90 – 3. REAL-WORLD VEHICLE EMISSIONSWith Euro 6 compliant control technologies the situation is even more complex, in addition to EGR
most vehicles are equipped with additional after-treatment technology for NOx reduction. This is
typically a lean NOx trap (LNT) or a selective catalyst reduction (SCR) system. The latter uses a urea
solution (AdBlue) to reduce NOx to harmless components. For most Euro 6 vehicle models real-world
NOx emissions are still very high, but occasionally models are found with low emissions. The reasons
why a large number of diesel Euro 6 vehicles perform poorly on NOx emissions tests in many real-world
conditions vary from specific design and optimisation for the type-approval test to the limited robustnessof the emission control technology for the circumstances encountered in the real-world tests. In the firstcase the technology will never work properly in the full spectrum real-world usage. In the second caseimprovements may be expected. For the petrol three-way catalyst it also took about ten years for theemission control strategy to mature to full robustness, which also copes with emissions during most hard
accelerations.

Normal conditions of use as part of type-approval
European legislation already included a provision in 2007 to introduce on-road testing if theregulation based on type-approval tests in the laboratory proved insufficient to yield low real-world
emissions, described in the legislation as “normal conditions of use”. In 2011 the European Commission
started to develop real driving emissions (RDE) legislation because of the failure of Euro 5 cars andvans, sold from 2009 onwards, to reduce the on-road NOx emissions of diesel vehicles.
The RDE legislation took a long time to develop because of the stakeholders’ involvement in theprocess. However, since 1 September 2017 all new vehicle models should be tested on-road. Since the
manufacturer has freedom in the execution of the RDE test with the prototype vehicle, an essential
ingredient of RDE legislation is to challenge the declaration of compliance of the manufacturer by doing
independent testing in other, possibly more demanding conditions than chosen by the vehicle
manufacturer in consultation with the type-approval authority. The change in the regulations on
1 September 2017 is not expected to yield significant change for some time as new vehicle models canbe added to existing type-approvals. Only from 1 September 2019 will all new vehicles have to comply
with the RDE regulation and RDE tests become unavoidable for manufacturers to sell new vehicles.
There is optimism that RDE legislation will deliver a substantial reduction in NOx emissions andensure real-world emissions consistent with the type-approval limits for the foreseeable future. But RDE
legislation still lacks two important provisions. First, the final part of the RDE legislation, which covers
challenges to RDE type-approval declarations of compliance, has yet to be finalised. Second, there is noprovision for reform of European type-approval authorities, which is needed to make pan-European
enforcement of vehicle emission legislation possible. Moreover, the finer details of the RDE legislation
will determine how robust it is and this will only become apparent as it is implemented.

Impacts of driving conditions on emissions
Driving behaviour, congestion and speed limits can all affect the emissions of a vehicle
significantly. For vehicles already in use, influencing driving conditions is one of the few means bywhich exhaust emissions can be reduced.
The problem with congestion is the low velocity and the high vehicle dynamic range (acceleration
and braking). Below 50 km/h most emissions of a modern vehicle are associated with keeping the engine
running, rather than propelling the vehicle forward. Below 50 km/h therefore, halving the velocity
roughly doubles the emissions per kilometre. Simply said, the engine is operating twice as long if thevelocity is halved. The second effect is the higher dynamics associated with congestion. A large number

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3. REAL-WORLD VEHICLE EMISSIONS – 91

of stopping or braking events means that a larger part of the energy produced by the engine is not used
for getting from origin to destination but is converted into heat in the brakes. The low velocity and theincreased braking may double the emissions per kilometre in congested urban situations.
Hybrid vehicles are designed to deal more efficiently with the low velocity and high dynamics ofcongested traffic. In the case of hybrid vehicles the emissions do not increase as dramatically withincreasing congestion.
Reducing congestion to reduce emissions is seldom simple. In many cases the bottlenecks in the
traffic capacity of a road network are simply shifted in position rather than removed by measures tomanage congestion. This will shift the source of the emissions to a new location. In some cases shifting
the traffic congestion to another location is warranted, when it can reduce the actual exposure of citizens.
On the other end of the velocity range, above 90 km/h, engine power demand increases rapidly withspeed because of the air-drag on the vehicle. From 100 km/h to 150 km/h the fuel consumption typicallymore than doubles, and given the limited optimisation of the emission control technology for highvelocities the pollutant emissions will increase in many cases many times that amount. A factor of five or
more increase in pollutant emissions is not exceptional for velocities above 100 km/h.
Altogether, for modern light-duty vehicles driving constantly between 50 km/h and 90 km/h will
yield the lowest fuel consumption and the lowest pollutant emissions. In the Netherlands an 80 km/h
speed limit on motorways was introduced for the beltways of Amsterdam and Rotterdam to reduce
air-quality problems in the neighbourhoods within one kilometre of these motorways. Motorways have alarge effect on local air quality due to the 100 000 or more vehicles that can pass per day.

Emission measurement and modelling
The measurement of real-world emissions had to shift from laboratory tests to on-road emission
tests because of the elaborate vehicle emission control strategies. Even without an illegal defeat device,
vehicles can have very different emissions in normal on-road conditions than in the laboratory. Hence inthe assessment of the emissions performance of vehicles it is essential to replicate as well as possible thevariety of normal conditions on the road. A shift from a simple test to monitoring of vehicle emissions
over a longer time is important for grasping the effects over the full span of on-road conditions.
Since 2009 for heavy-duty vehicles and since 2011 for light-duty vehicles, on-road emissions
measurements are part of the determination of the average vehicle emissions for in Dutch air quality
models. The official emissions factor model, developed by TNO, is updated annually with the newmeasurement results from the previous year of emissions testing. Test results from at least ten different
common vehicles in the same emissions class are needed to provide a confident prediction of emissions
in a variety of circumstances, with as a rule of thumb, each vehicle undergoing at least a day of testingover about 600 km.

Impacts of malfunctioning and tampering
Occasionally a test vehicle performs very poorly because of malfunctioning, tampering,
deterioration, or poor maintenance. It is difficult to point to a single factor responsible for high emissions
from an older vehicle. Design, maintenance, usage and fuel quality all play a role. Hence, even with alarge measurement program it is difficult to have cars banned from the road because of measured highemissions. The manufacturer will point to the user, who, in turn, will point to the garage undertaking
maintenance. The garage will point to the annual inspection procedure and the inspection authority will

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92 – 3. REAL-WORLD VEHICLE EMISSIONS

point to the legislation. Eventually, nobody will have full responsibility for a poorly performing car.
Unlike safety issues, emission performance seems hardly enforceable in Europe. Even in the aftermath of
the scandal around diesel vehicles, and the common knowledge that certain vehicles have extremely highemissions, there has not been a backlash in enforcement. Basically, there is no proper legal framework todeal with violations of emission regulation.
The prohibition of the wilful removal of a diesel particulate filter, the use of inferior replacement
parts, or the switching-off of the EGR or AdBlue injection of an SCR system, can be enforced. However,it requires good legislation to separate harmless adaptions of the vehicle from adaptions which increase
emissions. Only a technically skilful enforcer can establish if a breach of the legislation has taken place.
This is not a trivial matter as high punitive sanctions are needed to ensure the limited risk of detection
yields sufficient deterrence. Measuring emissions reproducibly to establish with confidence a deviation,and its underlying cause, requires a professional inspection service. The typical emission limits inperiodical inspections are factors higher than the emission limits in type approval tests.
Tampering exists in Europe, but the magnitude of the problem is largely unknown. There is noproper enforcement against tampering in place anywhere in Europe, unlike the US, where the EPA keeps
a full record of the proper state of in-use vehicles, including certification and registration of replacement
parts. The reasons for tampering are mainly cost related. The SCR is switched off to reduce the cost of
AdBlue refills. Switching off the AdBlue injection is not completely trivial, because of the on-board
diagnostics (OBD) control required by legislation. Likewise, the removal of a diesel particulate filter is
not a simple procedure. However, drivers, who drive mainly in urban areas below 80 km/h, may
encounter maintenance problems because of failed filter regeneration. Such regenerations should takeplace about every 500 kilometres and they require hot exhaust gas, produced typically with motorway
driving. If a vehicle does not enter the motorway often enough, the filter will be clogged and the engine
will stop working. Moreover, an uncontrolled regeneration may cause a vehicle fire. The expensive
maintenance of clogged filters can be avoided by removing the filter, with high particulate emissions as aresult.
Other forms of tampering are the closing off of clogged EGR that requires maintenance and the
flashing of the engine control unit for more engine power, probably at the expense of high emissions.
These two forms of tampering are usually done together as normal EGR control will not work in
conjunction with the power increase.

Impact of real-world emission performance on the effectiveness of local air quality policies
Reducing vehicle emissions with local measures to improve air quality has turned out to be difficult.
A decade of mitigation policies in Dutch cities to bring the ambient concentration levels below theEuropean air quality limits has found no silver bullets but instead many demanding measures were
implemented, each providing only a small positive reduction in emissions.
Many municipalities have introduced environmental zoning for traffic as a policy instrument forcurbing local emissions and improving air quality. In Europe many low emission zones are enforced on
the basis of vehicle emission legislation classes, banning older vehicles with higher legislative emission
limits. These limits may have little to do with the on-road emission performance of the vehicle, but they
can be properly registered and enforced.
The biggest hurdle is that vehicles, once allowed on the road, will be used for fifteen years or
longer. Any measure affecting the sales of new cars will not be effective for ten years or longer, as theolder vehicles dominate total emissions. The scrappage of older vehicles is usually not very cost effective

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3. REAL-WORLD VEHICLE EMISSIONS – 93

as a large number of older vehicles, each driven only a limited annual mileage, are together responsible
for the high emissions. The replacement vehicle in scrappage schemes may also not bring much
improvement. Measures on public transport buses, including fleet renewal or the introduction ofalterative propulsion technologies, are often most effective, as these vehicles drive a high mileage inareas where air quality is an issue.
Bringing the velocity of vehicles to a constant 50 to 90 km/h, at least on motorways, is the bestalternative that does not affect personal mobility negatively. Expanding the infrastructure capacity to
reduce congestion may yield a short-term benefit, but the increased road capacity will generally result inincreased traffic volumes within a few years. Road pricing and parking pricing may provide more
durable reductions in congestion.
The use of private cars is linked to personal freedom and economic activity. Hence the option tolimit the daily mileage of vehicles to reduce the total emissions and improve the air quality is not usuallyavailable. Other measures have to be taken to reduce the vehicle emissions. These measures come in fourgroups. The first measure is a long-term plan: stimulate new vehicles with clean technology possibly
enhanced by scrapping the oldest vehicles with the largest impact on air-quality. Second, reduce vehicle
use by stimulating clean public transport and alternatives like cycling. Third, enforce proper vehicle
maintenance and prevention of tampering. Finally, reduce congestion and bring traffic velocities to a
constant 50-90 km/h on motorways. A comprehensive package includes all four items, combined withcampaigns to generate public awareness of their personal contribution to public health and quality of life.

Conclusions
The three-way catalyst, introduced around 1990, has reduced the emissions of petrol vehicles tonegligible levels compared to diesel vehicles. The widespread application of DPFs from 2009 onwards
has reduced particulate emissions of diesels to extremely low levels, well below the emission limits.
Nevertheless real-world pollutant emissions of road vehicles are often significantly higher than thetype approval values. This is especially the case for NOx emissions from diesels. Between Euro 1 andEuro 5 standards the European NOx limit has decreased by a factor of five but real-world NOx emissions
have remained more or less constant.
High real-world NOx emissions from light- and heavy-duty diesels are the main cause of high NO2
concentrations in cities. The fact that newer light-duty vehicles are not significantly cleaner than older
Euro classes reduces the effectiveness of local policy measures, like low-emission zones, to reduce theNOx emissions of traffic. Some Euro 6 vehicles now show real-world NOx emissions closer to the limit,
but many vehicle models in real-world still exceed the limit by a factor of eight.
Given the fleet of vehicles on the road, implementing traffic measures that bring speeds to a moreconstant 50 to 90 km/h on motorways and ring roads is the most effective measure available to lower
tiers of governments for reducing traffic emissions.

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94 – 3. REAL-WORLD VEHICLE EMISSIONS

Annex 1.
TNO has undertaken emission testing for the Dutch government continuously since the 1980’s.
There are comprehensive programmes to test passenger cars, vans, trucks, buses and two-wheelers. The
main purpose of the measurement programmes is to determine the on-road, in-use emission performanceof vehicles relevant to Dutch air quality.16 The emissions factors for different road types and congestion
levels are updated annually on the basis of new measurement results. The reports and the results areavailable on-line. The table below summarises the main results for NOx and exhaust PM emissions(particulate mass).
Table A1. Main results of NOx and exhaust PM emissions

Particulates
(PM1)

NOx

Particulates
(PM1)

NOx

Particulates
(PM1)

NOx

Particulates(PM1)

PetrolDieselLight

Motorway[g/km][g/km][g/km][g/km][g/km][g/km][g/km]

Euro-1

1.29

0.108

0.72

0.067

0.47

0.00680.25

0.0025Euro-20.69

0.00460.47

0.00460.21

0.00230.20

0.0050Euro-30.21

0.00460.15

0.00460.059

0.00230.036

0.0050Euro-40.079

0.00460.054

0.00460.025

0.00230.015

0.0050Euro-50.063

0.00370.043

0.00370.020

0.00190.012

0.0050Euro-60.063

0.00370.043

0.00370.020

0.00190.012

0.0050Euro-1

1.92

0.372

1.06

0.236

0.45

0.101

0.69

0.081

Euro-2

1.10

0.162

0.80

0.111

0.55

0.045

0.67

0.092

Euro-3

1.23

0.043

0.80

0.031

0.55

0.026

0.70

0.052

Euro-4

0.69

0.051

0.43

0.033

0.38

0.016

0.51

0.035

Euro-51.00

0.00050.67

0.00050.53

0.00050.59

0.0015Euro-60.55

0.00050.43

0.00050.34

0.00050.41

0.0015Euro-6 RDE

0.31

0.00050.23

0.00050.17

0.00050.17

0.0015

pre-Euro

12.4

0.971

7.7

0.54

6.4

0.32737.0

0.27

Euro-1

8.1

0.477

5.0

0.26

4.2

0.15884.5

0.13

Euro-2

8.7

0.192

5.4

0.107

4.4

0.0771

4.6

0.067

Euro-3

10.3

0.224

5.7

0.124

3.9

0.07474.2

0.054

Euro-4

10.1

0.046

6.3

0.025

3.3

0.01383.3

0.0102Euro-5Euro-5 with
OBD

7.4

0.016

4.6

0.00992.8

0.00661.7

0.0055

7.5

0.014

4.7

0.00872.7

0.00571.8

0.0048Euro-6

0.44

0.010

0.28

0.00610.19

0.00420.17

0.0037Legislation

Passenger cars

Rural

[g/km]

Component

TrucksUrban normal

NOx

Urban congested

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3. REAL-WORLD VEHICLE EMISSIONS – 95

Table A1. Main results of NOx and exhaust PM emissions (continued)

Particulates
(PM1)

NOx

Particulates
(PM1)

NOx

Particulates
(PM1)

NOx

Particulates
(PM1)

Heavy

Motorway[g/km][g/km][g/km][g/km][g/km][g/km][g/km]

pre-Euro

33.6

2.49

21.0

1.38

15.0

0.82

13.3

0.63

Euro-1

22.1

1.29

13.8

0.72

9.9

0.41

8.5

0.32

Euro-2

23.3

0.56

14.6

0.31

10.2

0.19

8.8

0.16

Euro-3

28.0

0.55

15.6

0.30

9.4

0.17

8.3

0.13

Euro-4

24.1

0.110

15.1

0.061

7.9

0.031

7.9

0.023

Euro-5Euro-5 with
OBD

18.8

0.044

11.7

0.028

6.6

0.021

3.9

0.0162

16.3

0.041

10.2

0.026

5.6

0.017

3.7

0.0131Euro-6

1.37

0.030

0.86

0.019

0.56

0.012

0.46

0.0101

pre-Euro

27.0

2.10

16.9

1.13

12.4

0.65

11.3

0.50

Euro-1

21.6

0.90

13.5

0.48

9.0

0.31

6.3

0.22

Euro-2

19.6

0.58

12.2

0.31

8.1

0.28

6.5

0.111

Euro-3

17.2

0.43

10.8

0.23

6.3

0.19

4.4

0.109

Euro-4

13.3

0.18

8.3

0.098

4.2

0.043

3.0

0.019

Euro-5

7.18

0.153

4.5

0.075

2.3

0.051

1.6

0.051

Euro-6

1.11

0.015

0.69

0.015

0.42

0.0091

0.33

0.007

Legislation

TrucksRural[g/km]

Component

BussesUrban normal

NOx

Urban congested

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REFERENCES – 97

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102 – LIST OF PARTICIPANTS

List of participants
Mexico City Government
Miguel Ángel MANCERA
Mayor
Mexico City
Tanya MÜLLER GARCÍA
Secretary of Environment
Mexico City
Beatriz CÁRDENAS
Director-General
Air Quality Management
Candi DOMINGUEZ
Director of Sustainable Transport Programme and Mobile Sources
Air Quality Management
Vania TERRONES
Responsible for the Environmental Self-Regulation Programme for Diesel Vehicles.
Air Quality Management
Rubí E. SÁNCHEZTechnical Responsible for the Alternative Fuels Programme
Air Quality Management
César F. GÁLVEZ
Deputy Director of Sustainable Transport Promotion
Air Quality Management
Patricia CAMACHO
Director of Air Quality Programs and Emissions Inventory
Air Quality Management
Eunice CORTÉSTechnical Coordinator
Air Quality Management
Antonio GALVAN
Deputy Director of Mobile Sources
Air Quality Management
Jose Luis HERNANDEZ
Technical Responsible for the Mobile Source Measurement Programme
Air Quality Management
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LIST OF PARTICIPANTS – 103

Petra PAZ
Emissions Inventory
Air Quality Management
Olivia RIVERA
Atmospheric Monitoring
Air Quality Management
David USCANGA
Special Mobile Sources Programmes
Air Quality Management
Oscar VÁZQUEZ
Director of Climate Change Programme and Projects on Clean Development Mechanisms
Air Quality Management
International Experts
Olimpio ALVARESCAFDevelopment Bank of Latin America
Kate BLUMBERG
Senior Fellow & Mexico Lead
International Council on Clean Transportation (ICCT)
United States of America
Leo CARROLL
Hager Environmental & Atmospheric Technologies (HEAT)
United States of America
Claire CHERIYAN
Transport for London (TfL)
United Kingdom
Pan HAIXIAO
Tongji University
China
Ulises HERNÁNDEZ
International Council on Clean Transportation (ICCT)
United States of America
Nobutoshi HORIE
Senior Officer for Maintenance Promotion
Ministry of land, Infrastructure, Transport and Tourism
Japan

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104 – LIST OF PARTICIPANTS

Jorge KOGAN
CAFDevelopment Bank of Latin America
Pierre LADA
Mairie de Paris
FranceNorbert LIGTERINKTNONetherlands
Gianni LOPEZ
Centro Mario Molina, Santiago
Chile
Allen LYONS
California Air Resources Board
United States of America
Gustavo MAÑEZ
UN Environment
PanamaElsa MARTAYAN
Mairie de Paris
FranceAndreas MAYER
Technik Thermische Maschinen (TTM)
Switzerland
Aliosha REINOSOCAFDevelopment Bank of Latin America
Georg SCHMID
GIZ, Washington
Germany
Harvey SCORCIACAFDevelopment Bank of Latin America
Valentino SEVINO
Agency for Mobility Environment and Territory (AMAT)City of Milan
Italy

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LIST OF PARTICIPANTS – 105

Eduardo VASCONCELLOSCAFDevelopment Bank of Latin America
Experts from Mexico
Andrés AGUILAR
INECC
Bernardo BARANDA
ITDPFrancisco J. BARRERA
Government of the State of Mexico
Laura I. CASTILLO
Mobility System, Mexico City
José Luis CORTÉS
Government of Puebla
Verónica GARIBAY
Consultant
Rogelio GONZÁLEZ
UNAM
Martín A. GUTIÉRREZ
CAMeRodolfo INIESTRAINECCJorge MACÍAS
WRI Mexico
Stephanie MONTERO
Government of Morelos
Gabriela NIÑOConsultant
Eduardo OLIVARESSEMARNAT
Manuel F. OLIVERA
C40
Víctor Hugo PÁRAMOINECC

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106 – LIST OF PARTICIPANTS

Rodrigo PERRUSQUIAINECCBenjamín RICO
Government of Hidalgo
Sergio SÁNCHEZ
Clean Air Initiative
Judith TRUJILLOSEMARNAT
International Transport Forum
Stephen PERKINSHead of Research & Policy Analysis
Aimee AGUILAR JABER
Economist
Bernardo VAZQUEZ
Junior Consultant
Monserrat FONBONNATAssistant

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NOTES – 107

Notes

1 1

The Metropolitan Area of Valle de México is composed by Mexico City, 59 municipalities of the State of
Mexico and one municipality from the State of Hidalgo, as defined by the National Population Council(CONAPO). Some of the principal environmental protection measures, such as the periodic motor
vehicle inspection and maintenance programme, the Hoy No Circula system of restrictions on the use ofvehicles and the air pollution alert plan are applied over a smaller area, defining the ZMVM as Mexico
City and 18 municipalities of the State of Mexico.

2

The US heavy-duty vehicle standards were set in 2007 with a phase in of stricter NO x limits that became binding
only in 2010. The standards are therefore generally referred to as EPA 2010 even if this is not strictly
accurate.

3

NOx and PM control technologies on light duty diesel vehicles have also suffered performance problems in urban
use, see Chapter 3.

4Under Euro 5 light-duty vehicle standards, gasoline cars were subject to a very low mass limit for particulate
emissions, 5 mg/km. US Tier 2 and 3 regulations include a similar limit. Under Euro 6 standards thenumber of particles emitted per km is identical for gasoline and diesel cars. For heavy duty vehicles,
particle numbers have been regulated since Euro VI regulations in 2013.

5

As noted, the damage done by particulates depends on the metals and other toxic molecules attached to them.
Particle filters with catalytic surfaces have been developed, notably for use in heavy equipment for
tunnelling, which can strip off many toxic contaminants and offer a more effective approach tocontrolling particulate emissions in the future. Such filters are available for retrofit on any heavy vehicle
and have been installed for example on buses in Madrid and Barcelona. This technology promises a more
effective route to limiting emissions in all types of engine.

6

Wikipaedia provides summarises requirements in a range of countries with reasonably up to date information:
https://en.wikipedia.org/wiki/Vehicle_inspection
https://en.wikipedia.org/wiki/Vehicle_inspection_in_the_United_States

7

The governing body is composed by Minister of Environment and Natural Resources, the Mayor of Mexico Cityand the Governors of the States of Hidalgo, Mexico, Morelos, Puebla, and Tlaxcala (…).

8

Available at http://www.aire.cdmx.gob.mx/default.php?ref=Ym-Q=

9

Ultraviolet (NOx) and infrared (CO, CO2, HC) laser light absorption sampling of exhaust plumes as cars drive by
sensors installed at the roadside.

10

The Emission Reduction Comprehensive Program (PIREC) works through two main mechanisms: freesubstitution of catalytic converters for vehicles that are over 15 years old, and for more recent models
that have declared failures on their catalytic converters during vehicle verification tests.

11

Atizapán de Zaragoza, Cuautitlán, Chalco, Ecatepec de Morelos, Naucalpan de Juárez, Chicoloapan, Tecámac,Tultitlán, Cuautitlán Izcalli, Chimalhuacán, Huixquilucan, La Paz, Nezahualcóyotl, Nicolás Romero,Tlalnepantla de Baz y Valle de Chalco.

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108 – NOTES

12The Megalopolis region is comprised by 12 metropolitan areas: Mexico City, Puebla-Tlaxcala, Toluca,
Cuernavaca, Pachuca, Tlaxcala-Apizaco, Cuautla, Tehuacán, Tulancingo, Tula, Tianguistenco andTeziutlán.

13

It is important to remark that this payment is substantial enough to be used in exceptions, such as emergencies orwhen a vehicle has to access on a seldom fashion. If the payment amount is designed as an incentive tobe granted access, but a considerable number of units opt for paying it, we would stand before acongestion charge scheme and not a low emission zone.

14

The selection of these low emission zones is based on their representativeness, but it is primarily based on theirrelevance as better practice studies. Stockholm was the first LEZ implemented in Europe, so there has
been a considerable amount of time to study its effects. London is possibly the most know LEZ and themost studied one. Berlin represents the increasing number of German cities that are implementing thesezones. Finally, Milan is a case of regional implementation that has a relatively different scheme,
compared to more known LEZs across Europe.

15

For more information and reports see:https://www.tno.nl/en/focus-areas/urbanisation/mobility-logistics/clean-mobility/emissions-of-nitrogenoxides-of-diesel-vehicles/
https://www.tno.nl/en/about-tno/dossiers-in-the-news/real-world-vehicle-emissions/
https://www.tno.nl/en/focus-areas/urbanisation/mobility-logistics/clean-mobility/measuring-theemissions-of-passenger-cars-and-vans/
https://www.tno.nl/en/focus-areas/urbanisation/mobility-logistics/clean-mobility/measuring-theemissions-of-trucks-and-buses/
https://www.tno.nl/en/focus-areas/urbanisation/mobility-logistics/clean-mobility/emissions-ofparticulate-matter-from-diesel-cars/
https://www.tno.nl/en/focus-areas/urbanisation/mobility-logistics/clean-mobility/emission-factors-forroad-traffic/
http://www.ermes-group.eu/web/reports_and_publications

16

The Dutch national emission inventory can be found at:
http://www.emissieregistratie.nl/erpubliek/bumper.en.aspx
For Europe the European Environmental Agency keeps track of the state of affairs, collecting the datafrom the member states: http://www.eea.europa.eu/

STRATEGIES FOR MITIGATING AIR POLLUTION IN MEXICO CITY — © OECD/ITF 2017

Strategies for Mitigating Air Pollution
in Mexico City

2017-04/Photo credit: Mexico City on a clear day, SEDEMA/Enrique Abe

International best practice