Estimation of Paved and Un

Estimation of Paved and Un

Road Dust Emissions in M

Road Dust Emissions in M

Marty Wolf and Paula Fields Marty Wolf and Paula Fields

ERG, Inc. ERG, Inc.

Sacramento, CA Sacramento, CA

Salvador González Salvador González

-Ayala

International Communities Research Center International Communities Research Center

El Paso, TX El Paso, TX

NARSTO Emissions Inv

NARSTO Emissions Inv

Oc

Oc
Mexico National Emissio

Mexico National Emissio

Inventory Inventory 

- Characteristi

Characteristi

• Multi

-year development year development

• 1999 criteria pollutant base year inven

1999 criteria pollutant base year inven

for entire country at municipality level for entire country at municipality leve

• Multi

-phase release phase release

– Draft inventory Draft inventory 

- released July 2003 released July 2003

– Draft final inventory Draft final inventory 

- expected Spring 2

expected Spring 2

– Final inventory Final inventory 

- expected Summer 2004 expected Summer 2004
On-Road Mobile Source

Road Mobile Source

in Mexico in Mexico 

• Mexico population Mexico population - 97 million 97 million• Vehicle population Vehicle population - 18 million 18 million

• VKT estimates needed for entire coun

VKT estimates needed for entire coun

municipality municipality-level, but limited data level, but limited data 

availability availability

• No existing estimates for VKT split No existing estimates for VKT split 

between paved and unpaved roads between paved and unpaved roads
Methodology Steps Methodology Steps 

• Traffic volume and congestion modeli

Traffic volume and congestion modeli

representative urban areas representative urban areas

• Determine daily per capita VKT for ea

Determine daily per capita VKT for ea

representative urban area representative urban area

• Link

-specific traffic volumes combine

specific traffic volumes combine

with paved/unpaved road data to deter

with paved/unpaved road data to deter

paved and unpaved VKT split paved and unpaved VKT split
Representative Urban Are

Representative Urban Are

City/Town Class Population Range Represen

 Urban A

Small Town <25,000 Castaños, CoahuMedium Town 25,000 – 100,000 Río Bravo, TamLarge Town 100,000 – 250,000 Ensenada, Baja Small City 250,000 – 1,000,000 Hermosillo, SonMedium City 1,000,000 – 2,000,000 Ciudad Juárez, CLarge City 2,000,000+ Monterrey, NueMexico City Mexico City 
Traffic Volume and Traffic Volume and

Congestion Modeling Congestion Modeling 

• Ciudad Juárez disaggregated trip generation 

Ciudad Juárez disaggregated trip generation 

• Zone

-level structure developed for each are

level structure developed for each are

• Zone

-level trip generations estimated using level trip generations estimated using 

statistics statistics 

• Trip productions and trip attractions balance

Trip productions and trip attractions balance

• Roadway network developed to distribute tr

Roadway network developed to distribute tr

• Links assigned function class, flow direction

Links assigned function class, flow direction

capacity, and average daily speed capacity, and average daily speed
Zone-Level Structure Level Structure -

Hermosillo Hermosillo
Primary Roadway Networ

Primary Roadway Networ

Hermosillo Hermosillo
Traffic Volume and Conges

Traffic Volume and Conges

Modeling Modeling 

- Cont.

• Transportation engineering gravity mo

Transportation engineering gravity mo

applied applied

• Person

-trips converted to vehicle trips converted to vehicle

-trips

• Iterative solution for gravity model Iterative solution for gravity model• Generate link Generate link-level loaded network level loaded network
Loaded Network Loaded Network 

- Hermos

Hermos
Estimation of Per Capita V

Estimation of Per Capita V

• VKTlink = Volume = Volumelink × Length × Lengthlink• VKTTotal = 

Σ(VKTlink

)

• Per Capita VKT = VKT Per Capita VKT = VKTTotal/Population /Population
Per Capita VKT Per Capita VKT

Representative Urban Area Daily Per Capita V

Castaños 1.9 

Río Bravo 1.6 

Ensenada 4.3 

Hermosillo 5.2 

Ciudad Juárez 6.2 

Monterrey 9.4 

Mexico City 6.3 
Methodology for Estimati

Methodology for Estimat

Paved/Unpaved Road VKT 

Paved/Unpaved Road VKT 

• Link level VKT estimated for represen

Link level VKT estimated for represen

urban areas urban areas

• Paved/unpaved road information obtai

Paved/unpaved road information obtai

for each representative urban area for each representative urban area

• Link level VKT and paved/unpaved ro

Link level VKT and paved/unpaved ro

information overlaid to determine information overlaid to determine paved/unpaved road VKT split paved/unpaved road VKT split
Paved/Unpaved Road Paved/Unpaved Road 

Information Information

• Existing GIS Existing GIS 

- Ciudad Juárez Ciudad Juárez

• Field Mapping Field Mapping 

- Castaños and Río Bra

Castaños and Río Bra

• Satellite Images Satellite Images 

- Ensenada and Herm

Ensenada and Herm

• Aerial Photographs Aerial Photographs 

- Monterrey and M

Monterrey and M

City
Paved/Unpaved Roads Paved/Unpaved Roads 

Hermosillo Hermosillo

unpaved unpavedpaved paved
Paved/Unpaved VKT Spli

Paved/Unpaved VKT Spl

Representative 

Urban Area 

Paved/Unpaved 

Surface Area Split

Paved/U

VKT 

Castaños 0.16/0.84 0.74/

Río Bravo 0.46/0.54 0.83/

Ensenada 0.50/0.50 0.92/

Hermosillo 0.65/0.35 0.97/

Ciudad Juárez 0.49/0.51 0.95/

Monterrey pending pend

Mexico City pending pend
Mexico VKT Estimates Mexico VKT Estimates

• Total VKT = 155.0 billion VKT/year Total VKT = 155.0 billion VKT/year

• Paved Road VKT = 144.4 billion VKT

Paved Road VKT = 144.4 billion VKT

(93.1%) (93.1%)

• Unpaved Road VKT = 10.7 billion Unpaved Road VKT = 10.7 billion 

VKT/year (6.9%) VKT/year (6.9%)
Emission Factors Emission Factors

• Estimated using AP Estimated using AP

-42 emission facto

42 emission facto

equations (Sections 13.2.1 and 13.2.2) equations (Sections 13.2.1 and 13.2.2)

• Silt loading, vehicle weight, silt conten

Silt loading, vehicle weight, silt conten

soil moisture soil moisture 

- currently using values f

currently using values f

Ciudad Juárez Ciudad Juárez

• Working to incorporate the effects of Working to incorporate the effects of 

precipitation and transport fraction precipitation and transport fraction
Comparison of Paved an

Comparison of Paved an

Unpaved Road Dust Emiss

Unpaved Road Dust Emiss

Inventory Area PM10 (Mg/yr) PM2.5 

U.S. Border Paved 389,303 97

Mexico Border Paved 100,581 24

U.S. Border Unpaved 2,183,916 32

Mexico Border Unpaved 469,935 68
Summary Summary

• Methodology useful for areas with limited v

Methodology useful for areas with limited v

activity data activity data

• Emissions can be developed for a large num

Emissions can be developed for a large num

municipalities, while focusing data collectio

municipalities, while focusing data collectio

small number of representative areas small number of representative areas

• Different types of paved/unpaved road Different types of paved/unpaved road 

information can be used information can be used

• Emission estimates can be improved with m

Emission estimates can be improved with m

location location-specific data specific data