United States

Environmental Protection

Agency

Air and Radiation EPA420-P-99-002

August 1999

M6.SPD.002

Facility-Specific

Speed Correction Factors

Draft

 Printed on Recycled Paper
EPA420-P-99-002

August 1999

Facility-Specific Speed Correction Factors

Draft

Report Number M6.SPD.002

David J. Brzezinski

Phil Enns

Constance J. Hart

Assessment and Modeling Division

Office of Mobile Sources

U.S. Environmental Protection Agency

NOTICE

This technical report does not necessarily represent final EPA decisions or positions.

It is intended to present technical analysis of issues using data which are currently available.

The purpose in the release of such reports is to facilitate the exchange of

technical information and to inform the public of technical developments which

may form the basis for a final EPA decision, position, or regulatory action.
Table Of Contents

1.0 ABSTRACT AND SUMMARY ............................................1

2.0 BACKGROUND ........................................................3

3.0 VEHICLE TESTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

3.1 New Driving Cycles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

3.2 Sample Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3.3 Vehicle Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

4.0 STATISTICAL ANALYSES ...............................................7

4.1 Emitter Status .....................................................9

4.2 Roadway Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

4.3 Vehicle Class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

4.4 Emission Standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

4.5 Convergence of Freeways and Arterial/Collectors . . . . . . . . . . . . . . . . . . . . . . . 12

4.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

5.0 EMISSION LEVEL CALCULATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

5.1 Freeway Versus Arterial/Collector Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

5.1.1 High Speeds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

5.1.2 Intermediate Speed Freeways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

5.1.3 Low Speed Freeways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

5.1.4 Arterial/Collectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

5.1.5 Extremely Low Speeds and Idle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

5.2 Local Roadways and Freeway Ramps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

5.3 Special Cases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

6.0 SPEED CORRECTION FACTORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

6.1 Basic Modeling Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

6.2 Emission Offsets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

6.2.1 Freeway Emission Offset Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

6.2.2 Arterial/Collector Emission Offset Calculation . . . . . . . . . . . . . . . . . . . . 20

6.3 Calculating Speed Correction Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

6.4 Effect of the NLEV Standards and the Supplemental FTP . . . . . . . . . . . . . . . . . 21

6.5 Application in MOBILE6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

7.0 COMPARISON TO MOBILE5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

8.0 COMMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

Appendices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
DRAFT M6.SPD.002h 1 August 24, 1999

1.0 ABSTRACT AND SUMMARY

Abstract

In MOBILE5, adjustments were made to the basic exhaust emission estimates to account

for the effects of area wide average trip speeds using speed correction factors developed from a

number of driving cycles with varying average speeds. For MOBILE6 we propose to adjust for

differences in driving behavior versus roadway (facility) type and aggressive driving effects as

well as average speed. EPA has developed new facility-specific inventory driving cycles, based

on real-world driving studies, and tested vehicles using these cycles to address these purposes. 

This report describes the analysis of the new driving cycle data and presents the resulting speed

correction factors proposed for use in MOBILE6.

Summary

Although the adjustments described in this document are called “speed” correction

factors, the adjustments include all of the effects on emissions caused by differences in driving

behavior, of which average speed is the most obvious and easiest to measure. The speed

correction factors described in this document are proposed to be used in MOBILE6 to replace the

speed correction factors now used in MOBILE5 for all light duty passenger cars and light duty

trucks of all model years and technologies. The speed correction factors for heavy duty vehicles,

diesel fueled vehicles and motorcycles from MOBILE5 would be retained for use in MOBILE6. 

This document also proposes a method for applying the new speed correction factors to future

technology vehicles for which no data is yet available.

The new MOBILE6 speed correction factors specifically account for aggressive driving

behavior not represented in older driving cycles. They also allow for evaluation of vehicle

emissions by roadway type (facility) and by roadway segments (links). There are four roadway

types modeled in MOBILE6:

 Freeways

 Arterial/Collectors

 Freeway Ramps

 Local Roadways

The proposed speed correction factors for freeways and arterial/collectors depend on both

speed and basic emissions level of the vehicles. The correction factors for freeway ramps and

local roadways depend only on emission level and cannot be adjusted for average speeds

different than the national average. All speed corrections are based on new driving cycles

designed to reflect real-world driving behavior, including the effects of aggressive driving not

found in the standard vehicle FTP certification driving cycle (Urban Dynamometer Driving

Cycle) and most older driving cycles used in emission testing.
DRAFT M6.SPD.002h 2 August 24, 1999

 Since the data for this analysis was collected using the new, realistic driving cycles, an

emission impact of aggressive driving is included in the effect of the new speed correction

factors on emissions. The introduction of the new Supplemental FTP (SFTP) into vehicle

emission certification will require the reduction of the emission effects from aggressive driving

for future vehicle certification. The impact of the SFTP on emissions will be addressed in a

separate document.

Table 16 contains our proposed speed correction factors for freeways. Table 17 contains

the proposed speed correction factors for arterial/collector roadways. For MOBILE6, the

correction factor for Local Roadways and Freeway Ramps assume a national average speed and

will not have an adjustment for local average speeds. The speed correction factors for freeways

and arterial/collectors converge below 7.1 mph and at higher speeds, depending on the pollutant

and emission level. At those points the freeway and arterial/collector speed correction factors

become identical. The speed correction factors for speeds below 7.1 mph will remain the same

as in MOBILE5, adjusted to account for the difference between the old and new speed correction

factors where they intersect at 7.1 mph.

MOBILE5 did not model average speeds above 65 miles per hour. The new driving

cycles also do not address average speeds above 65 miles per hour. EPA will consider whether

sufficient information is available to model average speeds above 65 miles per hour in MOBILE6

and will present any proposals for these higher speeds in a separate document. As in MOBILE5,

MOBILE6 will not explicitly address average speeds less than 2.5 miles per hour. Idle emissions

will be assumed to be the same as the grams per hour emitted at an average speed of 2.5 miles

per hour. This “idle” emission rate will be available as an output from MOBILE6.

Table 13 shows the coefficients used to calculate the freeway ramp and local roadway

emissions from the basic emission rate. Table 14 and 15 show the additive offsets used to

calculate the adjusted basic emission rate which is adjusted by the speed correction factors. 

Appendix B has an example calculation of the application of speed correction factors to the base

emissions calculated by MOBILE6.

Figures 4a through 4c show the effect of emission level on the speed correction factors. 

Figures 5a through 5c compare the new MOBILE6 speed correction factors with selected

MOBILE5 speed correction factors. Care should be taken in interpreting these figures, since

there are many differences in how these factors are applied in MOBILE6 as compared to

MOBILE5. These figures are discussed in more detail in Chapter 7.

The report is organized into sections which address various aspects of the analysis. 

Chapter 2 gives a brief background of the need for new, facility based, speed correction

factors.

Chapter 3 discusses the development of the facility cycles and the emission testing
DRAFT M6.SPD.002h 3 August 24, 1999

sample used in the development of the proposed speed correction factors.

Chapter 4 discusses the statistical analysis of the data sample.

Chapter 5 describes the approach developed to summarize the emissions data.

Chapter 6 uses the emission levels developed in Chapter 5 to develop the proposed speed

correction factors for MOBILE6.

Chapter 7 compares the speed correction factors developed in Chapter 6 to the existing

speed correction factors in MOBILE5.

Chapter 8 describes how to contact EPA in order to comment on this document.

EPA is requesting that MOBILE model stakeholders and other knowledgeable readers

comment on the methodology and validity of the assumptions used to determine the speed

correction factors proposed in this document.

2.0 BACKGROUND

 EPA's highway vehicle emission factor model, MOBILE, is used for inventory modeling. 

MOBILE has historically been based on emission testing using the Federal Test Procedure (FTP)

used to certify all light duty vehicles sold in the United States. The FTP uses a driving cycle (the

Urban Dynamometer Driving Cycle, commonly referred to as the LA4) which simulates urban

driving on a laboratory dynamometer. Correction factors for various conditions (e.g., average

speed, temperature, fuels) are applied to emissions measured at the FTP "standard" conditions. 

The speed correction factors were based on test results for vehicles tested on both the LA4

(Urban Dynamometer Driving Cycle) and several other cycles, each having a different average

speed. MOBILE6 will address two areas not adequately addressed in previous versions of the

model. These are real world driving behavior and the expanded use of transportation models in

determination of area-wide inventories.

"Real-World Driving"

The FTP has been used for emissions certification of all light duty vehicles sold in the

United States. The Clean Air Act Amendments of 1990 mandated a closer look at "real-world

driving" - that is, driving modes that are not covered by the FTP (and the Urban Dynamometer

Driving Cycle). EPA organized the Federal Test Procedure Review Project to address this

mandate. A new Supplemental FTP (SFTP) rule was finalized in October 1996. This rule

specifies the addition of a new certification cycle with more aggressive driving and associated

standards.
DRAFT M6.SPD.002h 4 August 24, 1999

MOBILE6 must address both the emission impacts of more aggressive driving than is

covered in the driving cycles that were used to develop MOBILE5 and the effects of the new

SFTP standards on future model year vehicles. A special EPA emission testing project was

initiated to address these concerns. The results of that testing are the basis for the analysis in this

document.

Transportation Models

The current and older versions of the MOBILE model were developed to estimate areawide emission inventories using trip-based emission estimates with trip-based adjustments for

average speed. Vehicle trips are defined as all driving from key-on to key-off, including a variety

of roadways and speeds.

Local officials have begun to integrate transportation models into their regional air quality

planning processes. Most transportation models represent the roadway system as a network of

"nodes," which are usually intersections, connected by "links," which represent a particular type

of roadway or "facility." Transportation models generate link-specific estimates of speed and

traffic volume. Transportation planners have begun using MOBILE to generate link-specific

emissions estimates for planning purposes.

Recent data from instrumented vehicles and chase car studies show that some types of

facility-specific driving contain more frequent and more extreme acceleration and deceleration

than others1. Different facilities may have similar average speeds, but may differ significantly in

the amount of steady cruise. These differences suggest that there is a need to quantify the

emission differences (if any) between facilities in order to evaluate facility-specific speed related

traffic control measures in inventory modeling. 

For example, at an average speed of 25 mph, travel over surface streets is likely have a

relatively low level of traffic congestion, but will include many stops for traffic signals. Travel

on a freeway at 25 mph may indicate a high congestion level, but may include fewer stops. 

MOBILE5's trip based emission estimates do not differentiate between roadway types. If these

models are used for each roadway separately, they would not account for any differences in

emissions resulting from these differences in driving behavior.

Other Approaches

California is also updating it’s highway emission factor model. However, California has

taken a different approach to modeling the effects of changes in vehicle speeds. Rather than

attempt to discern what the driving behavior is for various facilities at various average speeds,

they divide all observed driving into speed bins. Each bin contains “microtrips” with similar

average speeds, regardless of the roadway type where the driving was observed. By weighting

the results of the various speed bins, any areawide average speed can be modeled. Changes in

driving behavior can be modeled by varying the distribution of speeds.
DRAFT M6.SPD.002h 5 August 24, 1999

This approach requires areas to evaluate their fleet activity as “trips”, where individual

vehicles travel over a variety of roadway types at varying speeds to reach a destination. These

trips are then used to develop a distribution of average trip speeds. Transportation models

generally do not produce trip statistics and transportation planners would need to adjust their

models to generate these distributions. Any changes in the roadway system resulting in changes

in average speeds on specific roadways will require a change in the full areawide distribution of

trip speeds. Evaluation of the emission impact of changes in the specific roadways will require

new estimates of the areawide emission levels.

One important advantage of California’s approach is the need for fewer driving cycles. 

Given limited testing budgets, this allows more vehicles to be tested over each cycle, thus

increasing the statistical confidence in the emission test results. Development of the driving

cycles themselves requires fewer assumptions such as decisions about where and under what

conditions the observed driving occurred. The resulting trip-based California driving cycles are

also similar in concept to the trip-based Unified Driving Cycle (or LA92), which is used by

California as the basis for the highway vehicle emission factors. The approach we have proposed

for MOBILE6 requires more driving cycles with more detailed information about driving

conditions and location.

The most important disadvantage of California’s approach is the dependence on vehicle

trip information. Since vehicle trips occur over a variety of roadways at a variety of average

speeds, evaluation of trips is most relevant for only areawide emission estimates. The confidence

in the estimate of emissions will decrease as the size of the area to be modeled is decreased or if

only specific roadways or links are to be modeled. In addition, many transportation planners do

not currently generate trip speed distributions and other trip information from their models. This

will mean that changes will need to be made in the transportation models in many cases in order

to effectively use the California emission factors. In comparison, the approach proposed for

MOBILE6 is more compatible with analysis by roadway type and link. Since most transportation

models already estimate speeds and miles traveled by link, MOBILE6 will not normally require

major changes in the output from existing transportation models. Using MOBILE6, the areawide

emissions are still able to be estimated by compiling the results from the four roadway types.

A more detailed description of the California approach or a comparison of the two

approaches is beyond the scope of this document. Readers are encouraged to obtain information

directly from California to compare with the results documented in this report.

3.0 VEHICLE TESTING

3.1 New Driving Cycles

The basis for the analysis found in this report is a set of vehicles recruited and tested in

1997. The testing included new driving cycles specifically designed to address the effects of inuse driving behavior on emissions. Table 1 gives a brief description of the new cycles that were
DRAFT M6.SPD.002h 6 August 24, 1999

used in the testing. Collectively, these new driving schedules will be referred to in this document

as “facility” cycles. The driving behavior in each driving schedule is selected from data collected

from a particular roadway type during periods of various congestion levels. These congestion

levels have been roughly grouped into “levels of service” (LOS) using letters A through G,

similar to congestion category designations used in transportation models. Briefly, LOS “A”

refers to “free flow” (uncongested) situations and the subsequent letters indicate increasing levels

of congestion. The definition of these categories is discussed in more detail in a separate EPA

report describing the development of the new facility driving cycles1

.

 Table 2 compares the new cycles’ statistics to the target population statistics for each

cycle. The statistics for each cycle will differ from the statistics of the population of driving

which the cycle is designed to simulate (or “target population”). For example, the highest

average speed of the arterial/collector cycles is 24.8 mph. We know that driving on

arterial/collectors can have average speeds higher than that. The maximum speed of the

arterial/collector cycles is only 58.9 mph, while the maximum speed of the targeted population is

74.9 mph. This is a result of the cycle development process which chooses the best combination

of microtrips to match the target population. The microtrip which contains the maximum

observed speed may over-represent certain aspects of driving behavior and cannot be used within

the confines of a single driving cycle of limited duration.

Each cycle was designed to result in emission levels representative of the emissions we

would expect from the driving behavior observed in the target population. Characteristics which

were deemed important to the match were specific power, speed, and amount of acceleration,

deceleration and idle. The factor which most affects emissions, shown from previous experience

in development of the Supplemental FTP, is the power distribution. The average speed or

maximum speed of the resulting cycles may not exactly match the target population. More

importantly, however, the cycles approximate the power distribution of the target population. 

We feel that the emissions generated from the new cycles are a true representation of the

expected emissions from the driving behavior that was observed in the target population from

which the cycle was generated.

In addition to the new cycles described in Table 1, each vehicle was also tested using the

following cycles:

- Federal Test Procedure (FTP), with an additional hot running 505 seconds of the LA4

(Urban Dynamometer Driving Cycle).

- California Air Resources Boards (CARB) area-wide Unified Cycle (LA92).

- New York City Cycle (NYCC), a low speed cycle which has previously been used for

speed correction factors in the MOBILE model.

- ST01, a cycle based on instrumented vehicle data representing the beginning of trips

which is the first 258 seconds of the vehicle certification air conditioning cycle (SC03).

 Table 3 shows more information on these additional cycles. 
DRAFT M6.SPD.002h 7 August 24, 1999

3.2 Sample Selection

The vehicle sample for this analysis came from EPA Emission Factor testing performed

at both the Automotive Testing Laboratories, Inc. (ATL), in Ohio and EPA’s National Vehicle

and Fuels Emission Laboratory (NVFEL), in Ann Arbor, Michigan, in the spring of 1997. All of

the vehicles at ATL were recruited at Inspection and Maintenance lanes run by the State of Ohio,

and were tested in an as-received condition (without repairs). At the time of this analysis, a total

of 62 1983 through 1996 model year vehicles had been recruited and had completed testing in

Ohio, and 23 1990 through 1996 model year vehicles recruited and tested in Ann Arbor. The

sample of 85 vehicles includes 22 light-duty trucks. Most of the 85 vehicles were fuel injection,

with 3 carbureted passenger cars and 4 carbureted light duty trucks.

The vehicles tested at the EPA laboratory were recruited randomly. The vehicles tested at

ATL were selected as a stratified random sample, with strata corresponding to IM240 pass or fail

outcome determined at state run IM240 inspection stations in Ohio. ATL used the final phase-in

cutpoints recommended by EPA for use in I/M programs using the IM240 test procedure to

identify vehicles in need of maintenance. Twenty of the vehicles in the ATL sample failed the

IM240 test. Proper analysis of the ATL data requires careful weighting of the passing and failing

vehicles if emitter status is not considered as a factor in the analysis.

Table 4 shows the mix of EPA vehicle emission certification standards and fuel delivery

technology in the sample used in this analysis. Table 5 lists all of the vehicles individually,

showing vehicle make and model, odometer mileage, engine size and whether the vehicle passed

or failed an IM240 test procedure using final phase-in cutpoints. Table 6 shows the mix of

model years and vehicle class (car or truck) in the sample.

3.3 Vehicle Testing

All vehicles were tested in the as-received condition using vehicle certification test fuel. 

Testing of all cycles were done in random order to reduce any order bias. Vehicles were tested at

FTP ambient conditions. Emission results were measured both as composite “bags” and in

grams second by second. Only the bag results were used in this analysis.

4.0 STATISTICAL ANALYSES

The purpose of the testing using the new facility cycles was to determine the effects of

average speed on emissions using “real world” driving cycles. Separate cycles were developed

for freeway and arterial/collector roadways to allow comparison of those two roadway types. 

The testing program also “over sampled” high emitting vehicles in order to provide a sufficient

sample size to allow separate analysis of high emitting vehicles. Although vehicle mileage (or

vehicle age) is considered important for estimating emissions, it is not thought that vehicle

mileage is a factor in the effect of average speed on emissions. Together, the following testing
DRAFT M6.SPD.002h 8 August 24, 1999

and vehicle parameters were considered as potentially important in determining the effect of

average speed on emissions:

1. Emitter status.

2. Roadway type.

3. Vehicle class.

4. Exhaust Emission Standard.

The data from the vehicles tested using the new facility cycles were evaluated to

determine if the effect of the average speed on emissions differed significantly by these

parameters. The sections below (Sections 4.1 through 4.4) discuss the statistical results for each

parameter evaluated. Section 4.5 discusses the statistical support for the convergence of the

freeway and arterial/collector estimates. Section 4.6 summarizes the conclusions derived from

the statistical analysis. Chapter 5 describes the final proposed methodology.

Other factors were considered. Although there is a large range of model years (1983

through 1996 model years), the sample size (85 vehicles) was not sufficient for analysis explicitly

by model year or age. For the analysis, the difference in model years is assumed to be captured

by the difference in emission standards. 

Table 7(a-c) shows sample means and standard deviations for the combined dataset for

each cycle, stratified into high and normal emitter levels. A vehicle may be a Normal emitter for

one pollutant, but considered a High emitter for another. In some cases the sample sizes 

(Normal and High) do not sum to 85 vehicles. This is because some test results on some vehicles

were voided due to errors in the testing or sampling and could not be used. No valid emission

test results were eliminated from the analysis.

Figure 1(a-c) graphically shows the effects of average speed on emissions. Each point is

the ratio of the mean for the emissions of each of the 14 facility cycles versus mean emissions for

the LA4 (Urban Dynamometer Driving Cycle) for the same vehicles. The data show that the

high emitting vehicles do not exhibit as much sensitivity to speed, resulting in smaller ratios. 

It was expected that as the average speed increases the difference between emissions from

cycles representing arterial/collector roadways and emissions from cycles representing freeways

would decrease. A special analysis was done to confirm the observed convergence of freeway

and arterial/collector roadway emissions versus average speed. This analysis is discussed in

Section 4.5 below.

The method of analysis of variance was used to judge the effect of the above parameters

on the relation between average speed and emissions. The dependent variables in these analyses

were chosen to be the logarithm of grams-per-hour emissions. The grams-per-hour measure is

more stable than grams-per-mile, particularly at lower speeds, where very little distance is

traveled over a long time. The log transformation yields values that better satisfy the ANOVA
DRAFT M6.SPD.002h 9 August 24, 1999

test requirements of normally distributed constant-variance errors. In the actual fitting of speed

correction factor equations, described in Section 5, gram-per-hour units were used for analysis at

average speeds less than 30 mph. However, at high speeds (average speeds above 30 mph),

using a linear fit and grams per hour units, when converted back to grams per mile, forces a curve

shape which does not match the data trends. For speeds above 30 mph, gram per mile units were

used. 

Table 8 reports the ANOVA results in terms of p-values associated with tests of the

various factors described above. The p-value gives a concise way of judging statistical

significance. The p-value of a test is the smallest level of significance at which the null

hypothesis can be rejected. In these models, the null hypothesis states that the levels of a given

factor, e.g., roadway type, have equal effect on emissions. The level of significance for this test is

the probability of Type I error, i.e., of rejecting the null hypothesis when it is true, that is, of

falsely concluding that a difference exists. By convention, the level of significance is chosen to

be arbitrarily small, typically 0.05, in order to limit the occurrence of Type I error. If p is smaller

than the chosen level of significance, the null hypothesis is rejected in favor of the claim that a

difference exists.

For example, in comparing the normal and high emitter classes of total hydrocarbons,

Table 8 reveals a p-value of 0.000 for the main effect of the emitter class. In graphical terms, the

main effect captures the intercept of a line relating (log) emissions to speed. Thus, the small pvalue agrees with the rather obvious hypothesis that high emitters have different average

emissions than normal emitters. However, for the interaction of emitter class with speed, the pvalue is 0.1411, implying that difference in the slopes (the relationship between emissions versus

average speed) of the normal and high emitter lines (regressions) is not statistically significant.

Further, more detailed ANOVA results are shown in Appendix A at the end of this report. 

We now consider the statistical results for the individual factors.

4.1 Emitter Status

The sample was separated into “emitter status groups” based on their Hot Running LA4

exhaust emissions. Hot Running LA4 are emissions that would result from an FTP test which

does not include any engine starts. These emissions are intended to be the basic unit of exhaust

emissions for use in MOBILE61

. The emitter status groups were defined by the following

pass/fail cutpoints:

 0.8 g/mi Total Hydrocarbons (THC)

 15 g/mi Carbon Monoxide (CO)

 2.0 g/mi Oxides of Nitrogen (NOx)

These are the final phase-in cutpoints recommended by EPA for use in I/M programs

using the IM240 test procedure to identify vehicles in need of maintenance. A vehicle is
DRAFT M6.SPD.002h 10 August 24, 1999

considered a Normal emitter if its emissions are less than or equal to the cutpoint level for that

pollutant. It is considered a High emitter if its emissions exceed the cutpoint level for that

pollutant. Once a vehicle is identified by emitter status for a pollutant using the Hot Running

LA4 emission results, it is always categorized that way in this analysis, regardless of its emission

results on another driving cycle. The cutpoints were not used in combination. A vehicle could

be considered as a Normal emitter for the CO analysis even if it were designated as a High

emitter for NOx or THC.

 Table 8 confirms that the average emissions differ statistically by emitter class. The

speed variable also is significant, i.e., emissions vary with average speed. However, except for

CO, the emitter class-speed interaction is statistically non-significant.

While it is not always the case that the other factors - roadway type, vehicle type, and

emissions standard - interact statistically with emitter class, engineering judgement warrant

modeling these factors separately for normal and high emitters. Statistical conclusions for these

factors are presented next.

4.2 Roadway Type

For modeling in MOBILE6, four roadway types are considered: arterial/collectors,

freeways, freeway ramps and local roads. With arterial/collectors and freeways, the range of

average speeds in the facility cycles overlaps at speeds below 30 mph. At higher speeds, only

freeway cycles are available. The interaction between roadway type and vehicle type and

between roadway type and emission standard was examined.

Figure 2 (a-c) shows the effects of average speed on emissions in terms of the ratio of the

means for the emissions versus emissions for the LA4 (Urban Dynamometer Driving Cycle) for

normal emitting vehicles. The cycles representing freeway driving and arterial/collector driving

are connected with lines to show the difference in these road types versus average speed. The

Unified Cycle (LA92), the Area-wide Non-Freeway cycle, Local Roadway cycle and Freeway

Ramp cycle results are also shown in the figures. The same vehicles were tested on all cycles, so

differences between freeways and arterial/collectors are controlled for the vehicle effect.

The emissions data were compared statistically to determine if there is reason to model

arterial/collectors and freeways separately. The ANOVA results appear in Table 8. For all

pollutants in the normal emitter class, the main effects are statistically significant. The speed

interaction effects also are significant, albeit marginally so for hydrocarbons. Among high emitter

vehicles, only NOx exhibits a significant difference between the arterial/collector and freeway

road types. 

Since only freeway cycles are represented at speeds over 30 mph, no comparisons of

roadway type are required. Local roadways and freeway ramps are represented by only a single

cycle each and therefore cannot be analyzed for the effect of average speed.
DRAFT M6.SPD.002h 11 August 24, 1999

4.3 Vehicle Class

Of the 85 vehicles in the facility cycle sample, 22 are light duty trucks. The high emitters

among the trucks number three for NOx, six for CO and 10 for THC/NMHC. In the freeway and

arterial/collector roadway categories, for the normal emitters, the ANOVA results for passenger

cars versus light duty trucks in Table 8 show significant main effects. However, the interaction

with speed effects all are non-significant. For the high emitters, none of the vehicle type

comparisons is statistically significant at the 0.05 level.

For the local and freeway ramp driving cycles, the results are mixed for normal emitter

vehicles. NOx emissions differ at the 0.05 level on both cycles and CO is significant for the

ramp cycle. Among high emitters, vehicle type is not significant for any of the pollutants on

either cycle.

4.4 Emission Standard

It was expected that vehicles certified to the new Tier 1 exhaust emission standards would

exhibit a different response to average speed than the Tier 0 vehicles. Since the facility cycle

sample contains only 12 Tier 1 vehicles, a method was developed for increasing the sample size

by reclassifying a portion of the Tier 0 vehicles in the sample. Vehicles were defined as “Clean”

Tier 0 vehicles if their emissions were less than 70% of both the NMHC and NOx Tier 1

certification standard as measured on the standard FTP test. The Tier 1 standards are:

o NMHC standard: 0.25 g/mi (< 50,000 miles), 0.31 g/mi (>50,000 miles).

o NOx standard: 0.4 g/mi (< 50,000 miles), 0.6 g/mi (>50,000 miles). 

A total of eight clean Tier 0 vehicles were identified by this criterion. One Tier 0 vehicle

(number 5016) had low FTP Bag 1 and Bag 3 emissions and technically qualified for

reassignment. However, because it had large Bag 2 and IM240 emissions, it was not considered

representative of Tier 1 emission behavior and thus retained Tier 0 status under the new

definition. The clean Tier 0 vehicles were used both in the analysis of both Tier 0 and Tier 1

emission levels. Table 9 shows the subset of 20 vehicles used to represent Tier 1 emission

behavior. Tables 11 (a-d) show the average emissions for each driving cycle in the sample of

normal emitting Tier 0 vehicles, high emitting Tier 0 vehicles and the expanded sample of

vehicles considered normal emitting Tier 1 vehicles. Figure 3 (a-c) compares the Tier 0 and the

expanded Tier 1 sample of vehicles for the difference in the effects of average speed on

emissions. Emissions are shown in terms of the ratio of the means for the emissions versus

emissions for the LA4 (Urban Dynamometer Driving Cycle).

The ANOVA results in Table 8 compare emissions of the Tier 0 and Tier 1 vehicles for

the reallocated sample. On the arterial/collector and freeway cycles, for normal emitters the

emissions standard main effect is highly significant for all pollutants, and the interaction with

speed is significant for hydrocarbons. (The results are similar for the official emission standard
DRAFT M6.SPD.002h 12 August 24, 1999

classification.) For the local and freeway ramp facility cycles, all main effects are also significant.

There were no high emitter Tier 1 vehicles for any of the pollutants, so no test of the

standard factor can be made for that emitter class.

4.5 Convergence of Freeways and Arterial/Collectors

The data show a statistical difference between the freeway and arterial/collector cycles

below 30 mph, where the data overlaps. However, there are no arterial/collector cycles above

24.8 mph and there are no freeway cycles below 13.1 mph. If the speed correction factors for

both of these roadway types are to cover the entire spectrum of average speeds available in the

MOBILE6 model (0 to 65 mph), then some assumptions about the effect of average speed on

emissions will need to be made for the speeds outside the typical range for these roadways.

Based on the facility cycle emission testing results, it appears that as average speed

increases there is a decrease in the difference between emission results for arterial/collector

cycles and freeway cycles at the same average speed. This suggests, that above a certain average

speed, the same relationship between average speed and emissions can be used for both freeways

and arterial/collector roadways.

Support for the hypothesis that mean gram-per-hour emissions of arterial and highway

driving converge in the neighborhood of 30 mph can be found in the data from tests on the cycles

that represent these two forms of driving. Consider the following model of emissions:

Y = b0 + b1X + b2*D + b3X*D

where Y is emissions (in grams/hour) of a given pollutant; X is average speed of the cycle tested;

and D is a dummy variable representing road type (D = 0 for arterial, D = 1 for highway). This

equation effectively models two lines. When D = 0, the function estimates emissions versus

speed for arterials, with slope b1 and intercept b0. When D = 1, the line represents highway

emissions with slope (b1 + b3 ) and intercept (b0 + b2). 

This model is useful for examining differences between arterial and freeway emissions. 

The basic question of whether the linear functions differ is answered by testing the coefficients of

terms involving variable D. If both these coefficients ( b2 and b3) are zero, then the road types are

judged to be the same. For the 85 car sample, tests of this hypothesis are rejected for all

categories of emission standard and emission level.

Given that arterial and highway speed-emissions lines are significantly different, we now

ask if they differ at a chosen speed, e.g., 30 miles per hour. This is answered by constructing an

appropriate function of the linear model described above. When X = 30, the function becomes:
DRAFT M6.SPD.002h 13 August 24, 1999

Y = b0 + b1*30 for arterials

Y = b0 + b1*30 + b2*1 + b3*1*30

 = (b0 + b2) + (b1 + b3)*30 for highways

The two functions are identical when the linear combination b2 + b3*30 equals zero. This

hypothesis can be tested using the ESTIMATE feature of the SAS GLM procedure.

Table 10 presents results of these tests for Tier 0 normal and high emitters, and for Tier 1

normal emitters. At the five percent level, a significant difference is found in only in one case,

for Tier 0 normal CO emissions. This gives strong support for the claim that arterial/collector

roadway and freeway emissions are similar at speeds around 30 mph, even though their

relationship at average speeds below 30 mph is different. Based on this convergence, we propose

that the relationship between average speed and emissions for arterial/collector roadways and

freeways should be the same at average speeds above 30 mph.

4.6 Summary

The statistical analysis of the important parameters resulted in the following decisions

about how the data would be grouped for the MOBILE6 analysis:

Roadway Type

There will be different equations for the two roadway types (freeways and

arterial/collectors) for CO and NOx emission at both High and Normal emitter groups. There

will be different equations for the two roadway types for THC and NMHC emissions only for

normal emitting vehicles. Since the equations converge, there will be only one equation for all

roadway types and pollutants at average speeds above about 30 mph. The exact average speed

where the equations converge varies. For high emitting Tier 0 vehicles there will be no

difference between the two roadway types for THC and NMHC emissions at any average speed.

Vehicle Class

There will not be different equations for vehicle class (car versus truck). The equations

will depend on emission level (below), which will adequately cover any emission standard

differences between cars and trucks. Splitting the data by both emission standard (below) and

vehicle class would make sample sizes much too small for any meaningful results.

Emission Standard

There will be separate equations for Tier 0 and Tier 1 emission standard vehicles for

normal emission levels. There are no high emitting Tier 1 vehicles in the sample.
DRAFT M6.SPD.002h 14 August 24, 1999

Emission Levels

The Tier 0 emission standard data will be further separated by emitter status (Normal and

High) for all pollutants with separate speed equations for each. For the purpose of analysis, this

effectively results in three samples of vehicles representing three distinct emission levels:

 Level 1 : Tier 1 (Normal emitter)

 Level 2 : Tier 0 (Normal emitter)

 Level 3 : Tier 0 (High emitter)

5.0 EMISSION LEVEL CALCULATION

Once the appropriate aggregations for the existing data were determined as described in

the previous section, least square linear regressions were fit to the emission results versus

average speed. This was done in a “multi-linear” fashion, rather than using a single line or using

another non-linear curve shape. Attempts to fit non-linear curves to the total data sample

resulted in unacceptably high error coefficients. A linear fit of smaller groupings of the data

provided a closer fit to the data. A separate linear regression was done for different groupings of

cycles based on ranges of average speeds. Together, these lines will define the change in

emissions of the sample over the entire range of average speeds.

5.1 Freeway Versus Arterial/Collector Effects

As discussed in the previous section, the data show a statistical difference between the

freeway and arterial/collector cycles below 30 mph, where the data overlap. However, there are

no arterial/collector cycles above 24.8 mph and there are no freeway cycles below 13.1 mph. If

the speed correction factors for both of these roadway types are to cover the entire spectrum of

average speeds available in the MOBILE6 model (0 to 65 mph), then some assumptions about

the effect of average speed on emissions will need to be made for the speeds outside the range for

which we have data.

Logically, both curves will converge at idle (zero mph). Idling emissions should not

depend on roadway type. Also, it is logical to assume that driving which has a high average

speed must consist almost entirely of cruise with little stopping or idle, regardless of roadway

type. This suggests a model where freeways and arterial/collector roadways have different

emissions at normal arterial/collector average speeds, but have the same emissions at extremely

low speeds (and idle) and at higher speeds. Based on this model, we have defined the following

speed/facility segments:

o High Speeds (above about 30 mph) for both freeways and arterial/collectors.

o Intermediate Speed Freeways (from 13.1 to about 30 mph) for freeways.

o Low Speed Freeways (from 7.1 to 13.1 mph) for freeways.
DRAFT M6.SPD.002h 15 August 24, 1999

o Arterial/Collectors (from 7.1 to about 30 mph) for arterial/collectors.

o Extremely Low Speed and Idle (less than 7.1 mph) for both freeways and

arterial/collectors.

 We propose to use a combined emission estimate for both arterial/collector and freeway

facilities for THC and NMHC at the highest emission level. This will mean that, at high emitting

THC and NMHC emission levels, that there will be no emission difference between the two

facility types. There would still be separate freeway and arterial/collector estimates for CO and

NOx emissions at high emitting levels.

5.1.1 High Speeds

A regression was done of emissions versus average speed for the three emission

standard/emitter groups described above for the four freeway cycles with an average speed above

30 mph (Freeway at 30.5 mph, Freeway at 52.9 mph, Freeway at 59.7 mph and Freeway at 63.2

mph) in grams per mile for each pollutant. Tables 12a, 12b, 12c and 12d show the results of

those regressions. All of the slope coefficients of the regressions are statistically significant,

meaning that the increase or decrease in emissions versus average speed is different than zero. 

These regressions will be used to estimate the emissions of vehicles on both freeway and

arterial/collector roadways at average speeds above the point where the equations converge.

5.1.2 Intermediate Speed Freeways

A regression was done of emissions versus average speed for each of the emission

standard/emitter groups described above for the four freeway cycles representing freeway driving

in the most congested conditions (Freeway at 13.1 mph, Freeway at 18.6 mph and Freeway at

30.5 mph) in grams per hour for each pollutant. Tables 12a, 12b, 12c and 12d show the results of

those regressions. These regressions will be used to estimate the emissions of vehicles on

freeways between average speeds of 13.1 mph and about 30 mph. Note that the freeway cycle at

30.5 mph was included in both the intermediate speed freeway and high speed estimates. It is

expected that the two regressions should converge at about this average speed.

5.1.3 Low Speed Freeways

None of the existing facility cycles for freeway driving have an average speed below 13.1

mph. It will be assumed that at speeds lower than 7.1 mph (the average speed of the New York

City Cycle) the effect of average speed on emissions will be the same for freeways and

arterial/collector roadways. The emissions of freeway driving for average speeds between 13.1

mph and 7.1 mph will be calculated by linear interpolation between these emission levels in

grams per hour. Tables 12a, 12b, 12c and 12d show the resulting equations representing this

interpolation. Most freeway travel will occur at average speeds well above this range.
DRAFT M6.SPD.002h 16 August 24, 1999

5.1.4 Arterial/Collectors

The freeway cycle at 30.5 mph (already included in the freeway estimate) was included in

the arterial/collector roadway estimates as well. It was shown that the two regressions should

converge at about this average speed. The New York City Cycle was also included in the

arterial/collector roadway estimates. The New York City Cycle was not derived from the same

chase car or instrumented data used to develop the other facility cycles. However, the New York

City Cycle was originally developed as a speed correction cycle and, as shown in Table 3, does

contain acceleration rates higher than the contained in the LA4 (Urban Dynamometer Driving

Schedule). It was deemed that the New York City Cycle was representative of “real world”

driving and could be included in the analysis as another facility cycle.

A regression was done of emissions versus average speed for each of the emission

standard/emitter groups described above for the arterial/collector cycles (Arterial/Collector at

11.6 mph, Arterial/Collector at 19.2 mph, Arterial/Collector at 24.8 mph) in grams per hour for

each pollutant. Included in that regression was data from the New York City Cycle (with and

average speed of 7.1 mph) and the Freeway at 30.5 mph cycle for the same vehicles. 

Tables 12a, 12b, 12c and 12d show the results of those regressions. These regressions

will be used to estimate the emissions of vehicles on arterial/collector roadways in this range of

average speeds.

5.1.5 Extremely Low Speeds and Idle

No data was collected for the vehicles in the sample at speeds lower than 7.1 mph (the

average speed of the New York City Cycle). In this range the model will assume that the effect

of average speed on emissions will be the same for freeways and arterial/collector roadways. 

Since the MOBILE5 model already has estimates for the effect of average speed on vehicles at

speeds from 2.5 to 7.1 mph, and since there is no need to differentiate this effect by facility type,

the existing speed correction factors in MOBILE5 will be used for this range of average speeds

for both freeways and arterial/collectors. 

The MOBILE5 speed correction factors do not match the new proposed speed correction

factors at 7.1 mph. This discontinuity will be resolved by adding the difference in the two

estimates to values calculated using the old MOBILE5 speed correction factors. As in

MOBILE5, emissions at idle will be assumed to be the same (in grams per hour) as the emissions

at 2.5 mph (the lowest average speed modeled).

5.2 Local Roadways and Freeway Ramps

There is only one cycle each to represent driving on local roadways and freeway ramps. 

As a result, these cycles are not included in the analysis of emissions versus average speed. 

However, the data from these cycles were separated using the same sample splits by emission
DRAFT M6.SPD.002h 17 August 24, 1999

standard (Tier 0 versus Tier 1) and emitter status (Normal versus High) as are used for the

freeway and arterial/collectors. The average emission levels were analyzed as a linear function

of the base emission rate (hot running LA4 emissions). These regressions will be used to

estimate the emission levels for these roadway types as a function of the base emission rate

calculated in MOBILE6. The coefficients for these regressions are shown in Table 13.

5.3 Special Cases

Ideally, the equations above would define a rational, smooth relationship for emissions

versus average speed for the range of 0 to 65 mph for each pollutant based on the available data. 

However due to vagaries of using real-world data and the use of a multi-linear modeling

approach, some of the equations resulting from the general approach will cause small

discontinuities in the overall relationship. For example, the intermediate speed freeway emission

level for NOx (computed in gram per hour) does not intersect with the high speed freeway

emission level estimate (computed in grams per mile) at any speed. These discontinuities, when

examined, do not cast doubt on the overall relationship, but will require special handling to be

coded mathematically. A single smooth curve could be fit to the data over all speeds. This

would generate different and more difficult problems, however, such as an unacceptably poor fit

in certain speed ranges. For MOBILE6, some basic “rules” will be used to assure that there are

no abrupt or counter-intuitive changes in emissions versus average speed.

1) If at 30.5 mph, the emission estimate for the intermediate speed freeway equation is still

higher than the emissions for freeways calculated using the high speed equation, the

emission value calculated for 30.5 mph using the intermediate speed freeway equation

will be used for speeds greater than 30.5 mph until the value for the high speed equation

for that speed exceeds the intermediate speed freeway value. This rule keeps the

intermediate speed freeway value from increasing beyond the emission level calculated at

30.5 mph, which is the highest average speed data point used in the regression (no

extrapolations).

2) When calculating the emissions of an arterial/collector roadway, the arterial/collector

estimate for emissions will be used unless the estimate for freeways at that same speed

are higher than the arterial/collector estimate. This rule defines at what average speed the

arterial/collector and freeway emission estimates will converge. Above that speed the

arterial/collector and freeway emission estimates will be assumed to be the same. All of

the MOBILE6 arterial/collector equations intersect with the freeway estimate between 24

and 34 mph.

6.0 SPEED CORRECTION FACTORS

Using the methods in the previous section, the emission data can be described as a series

of continuous, smooth functions for the two roadway types (freeways and arterial/collectors) by

emission levels for all pollutants over the entire range of average speeds in MOBILE6 (2.5 to 65
DRAFT M6.SPD.002h 18 August 24, 1999

mph). This generalized relationship between emissions and average speed for any emission level

is referred to in the model as speed correction factors. These speed correction factors are the

values which will be stored and used in MOBILE6 to adjust the basic exhaust emission estimate

for average speed. Freeway ramps and local roadways, however, have only a single cycle and

cannot vary by average speed. MOBILE6 must also estimate speed effects for groups of vehicles

with basic emission rates that differ from those in the data sample.

6.1 Basic Modeling Approach

The basic exhaust emission rate generated by MOBILE6 will be based on a hot running

LA4 emission estimate with an average speed of 19.6 mph. In MOBILE6 Freeway Ramp and

Local Roadway emissions do not depend on speed and can be determined directly from the basic

exhaust emission rate. For freeways and arterial/collector roadways, the adjustment to account

for the average speed and facility type includes an multiplicative part and a additive part. The

multiplicative part accounts primarily for the difference in emissions due to changes in average

speed. The additive part accounts primarily for the difference between the basic emission rate,

based on the running emissions for the LA4 cycle, and the running emissions on the facility at the

same average speed. In MOBILE6, we propose that the basic emission rate be adjusted using the

following general method:

Adjusted BER = (BER + EO) * SCF + AEO

Where:

BER = Basic Emission Rate (running emissions for the LA4 cycle).

EO = Emission Offset (a function of BER emissions)

SCF = Multiplicative Speed Correction Factor (a function of speed and 

emissions).

AEO = Arterial/Collector Emission Offset (a function of speed and emissions).

For freeways, the AEO would be zero, since it only applies to arterial/collector roadways. 

Using the above equation, with a BER identical to the average hot running LA4 emissions of

each sample of vehicles in each of the three emission level groupings described in Section 4.6,

the estimate of emissions at any speed for each facility will match the average emission level

predicted by the regression equations from the facility cycle data from that vehicle sample. For

cases where the BER is not identical to the average hot running LA4 emissions of any of the

facility cycle sample emission level groupings, the EO will still be calculated as a function of the

BER, however the SCF and AEO adjustments will be interpolated using the three emission level

sample estimates. The interpolation would be determined by the emission level of the sum of the

BER and the EO. There are five cases:
DRAFT M6.SPD.002h 19 August 24, 1999

o If the emissions are between the Level 1 and the Level 2 emission levels, the SCF

and AEO factors would be interpolated between those two curves.

o If the emissions were between the Level 2 and the Level 3 emission levels, the

SCF and AEO factors would be interpolated between those two curves.

o If the emissions were equal to the Level 2 emission level, the Level 2 SCF and

AEO factors would be used.

o If the emissions were equal to or above Level 3 emission level, the Level 3 SCF

and AEO factors would be used.

o If the emissions were equal to or below Level 1 emission level, the Level 1 SCF

and AEO factors would be adjusted proportionally to the change in the BER and

accounting for differences in the emission standards. This will be discussed in

Section 6.4 below.

In this way, an emission offsets and an effect of average speed can be calculated for any

basic exhaust emission rate for any average speed allowed in MOBILE6 for each facility type.

6.2 Emission Offsets

In order to appropriately apply the multiplicative (proportional) speed correction factors

(SCF) of the form described in Section 6.1, first the basic exhaust running emission rate (BER)

must be adjusted to match the emissions observed on the freeway cycles at the same speed as the

BER (19.6 mph). All other speed adjustments are applied to this new, adjusted BER emission

level.

6.2.1 Freeway Emission Offset Calculation

The emission offset is simple in concept. It is simply the difference between the average

emissions of vehicles from the Hot Running LA4 cycle (the basis of the BER) and the predicted

average emissions of the same vehicles from the regressions using the freeway cycles from

Section 5.0 above.

Emission Offset = Freeway Cycle at 19.6 mph - Hot Running LA4 Cycle

The emission offset (EO) is calculated for each of the three emission levels (see Section

4.0). Table 14 shows the emission offsets calculated for the three emission levels. As described

in Section 6.1, the EO values can be adjusted to reflect any BER emission levels greater than

Level 1 directly by interpolation. Emission levels less than Level 1 (Tier 1) are discussed in

Section 6.4 below.
DRAFT M6.SPD.002h 20 August 24, 1999

6.2.2 Arterial/Collector Emission Offset Calculation

Arterial/collector cycles have higher emissions than freeway cycles at the same average

speed. For MOBILE6, we propose to account for this difference as an additional emission offset

effect, beyond that already accounted for by the freeway emissions estimate. Since the difference

between the emissions of arterial/collector cycles and freeway cycles varies with average speed,

this additional emission offset effect will be dependent on average speed.

AEO at X mph = Arterial/Collector emissions at X mph - Freeway emissions at X mph

The arterial/collector emission offset (AEO) is calculated for each of the three emission

levels (see Section 4.0). Table 15 shows the arterial/collector emission offsets calculated for the

three emission levels at each speed. As described in Section 6.1, the AEO values can be adjusted

to reflect any BER emission levels greater than Level 1 directly by interpolation. Emission levels

less than Level 1 (Tier 1) are discussed in Section 6.4 below. The AEO is always zero below 7.1

mph and above about 30 mph where arterial/collector and freeway estimates are identical. The

AEO is also zero for Level 3 THC and NMHC emissions, since the freeway and arterial/collector

emission estimates are the same for this emission level/pollutant.

6.3 Calculating Speed Correction Factors

As discussed in Section 6.2, for MOBILE6 we propose to adjust the basic exhaust

emission rates (BER) by first adding an emission value (emission offset, EO) to adjust the BER

to the level of the freeway emissions. This EO value will be a function of the basic exhaust

emission rate. An additional offset (the Arterial/Collector Emission Offset (AEO)) is added to

the freeway emission level to account for arterial/collector driving effects. The speed correction

factors are applied to the sum of the BER and the EO.

As the data has shown, the effect of average speed on emissions depends on emission

level. Therefore, the appropriate form for speed correction would be a multiplicative adjustment,

making the change in emissions due to change in average speed proportional to the basic exhaust

emission rate.

For MOBILE6, the speed correction factor (SCF) is defined as the ratio of the predicted

emissions at any average speed to the predicted emissions at 19.6 mph for freeways for the same

vehicle. The freeway emission levels are defined for all average speeds from 2.5 to 65 mph. 

Using the emission level equations described in Section 5, a set of SCFs will be determined for

each speed in increments of 5 mph beginning at 5 mph through 65 mph and at 2.5 mph for each

of the three emission levels within MOBILE6. These increments correspond to the proposed

increments of average speed for the VMT distribution for freeways and arterial/collector

roadways which we propose as input to MOBILE6. We propose to have MOBILE6 calculate
DRAFT M6.SPD.002h 21 August 24, 1999

these speed correction factors directly from the emission levels, rather than store the resultant

speed correction factors themselves. Table 16 shows the freeway SCF sets for the three emission

levels. These SCF sets are shown graphically in Figures 5a, 5b, 5c and 5d. Table 16 shows the

freeway emissions at 19.6 mph for each emission level. Table 17 shows the arterial/collector

SCF sets for the three emission levels.

Speed correction factors for emission levels below Level 1 (Tier 1) must account for the

effects of more stringent emission standards. This is discussed in Section 6.4 below.

6.4 Effect of the NLEV Standards and the Supplemental FTP

Starting in the 2001 model year, light-duty vehicles will be certified for sale using a new

test procedure, referred to as the Supplemental Federal Test Procedure (SFTP). Vehicles

certified using this test procedure will have lower emissions during typical driving than vehicles

certified using the current test procedures, primarily by requiring reductions in emissions during

hard accelerations and with accessory loads, like air conditioning. These vehicles will also have

to meet tighter National Low Emission Vehicle (NLEV) emission standards. The effects of

speed (including aggressive driving) on NLEV may differ from current vehicles. However,

speed corrections for NLEVs cannot be determined directly from the available NLEV emission

data. Not enough data on in-use NLEV vehicles is available yet.

The basic exhaust emission rates and emission offsets for NLEV will differ from Tier 1

vehicles in several ways. In addition to lower exhaust emission standards, the emission offsets

for normal emitting NLEV vehicles will be affected by the SFTP. Although high emitting

NLEV standard vehicles will have basic exhaust running emission rate (BER) emissions higher

than Level 1 (average emissions based on the sample of normal emitting Tier 1 vehicles), the

effect of the SFTP will likely reduce the offset for these vehicles as well. The amount of this

reduction will be addressed in a separate document describing the effects of the SFTP. It is

sufficient to know here that a separate set of emission offsets will be used for NLEV vehicles

which reflect the effect of the SFTP. 

In addition to the adjustments to the EO and AEO, the multiplicative speed correction

factors (SCF) for Level 1 (Tier 1) will also be adjusted to account for the change in emission

standards for basic exhaust running emission rates less than Level 1. Using the multiplicative

Level 1 SCF without adjustment would assume that the change in standards had affected all types

of driving behavior emission effects proportionally. If we compare the Tier 1 SCFs to the Tier 0

normal SCFs (as in Figures 5a-d), the effect appears to increase as emission levels decrease. It is

likely that NLEV standard vehicles should be more sensitive to changes in average speed than

Tier 1 vehicles.

An alternative to using the Tier 1 multiplicative SCFs would be to use the same change in

emissions observed in Tier 1 vehicles versus speed (additively) to represent the effects of speed

for NLEV standard vehicles. This additive approach would match the trend in SCFs, but
DRAFT M6.SPD.002h 22 August 24, 1999

assumes that there is no effect from new standards on the emission effects from changes in

average speed. It is likely that NLEV standard vehicles are less sensitive to changes in average

speed than estimated by the additive approach.

The two alternatives (multiplicative and additive) discussed above can be summarized as

the following two sets of equations:

SCFmult = SCFTier1

BERspeed = BER * SCFmult

and

SCFadd = (SCFTier1 - 1.0) * Tier 1 Sample Average Emission Level

BERspeed = BER + SCFadd

where

BERspeed is the speed corrected basic emission rate.

SCFmult is the speed correction factor assuming a multiplicative adjustment.

SCFadd is the speed correction factor assuming an additive adjustment.

SCFTier1 is the speed correction factor for Tier 1 vehicles at a given speed.

BER is the NLEV basic emission rate, unadjusted for speed.

Rather than choose between the additive and multiplicative approaches described above

for NLEV standard vehicles, we propose to choose SCF values that lie between these two

estimates. These SCFs would be used for all NLEV standard vehicles, and other vehicles with

emission standard levels less than Tier 1, regardless of emission level. We strongly encourage

readers to comment on this issue and propose alternate solutions to selecting SCFs for NLEV

standard vehicles.

6.5 Application in MOBILE6

We propose to apply the speed corrections described in this document to gasoline fueled,

light-duty vehicles (cars and light trucks) of all model years and technologies. The speed

correction factor would be applied to the basic exhaust hot running emission rates, adjusted to

freeway emission levels at 19.6 mph. Additional adjustment would be made to the freeway

emission estimate between 7.1 and about 30 mph to account for arterial/collector roadways. 

MOBILE6 would continue to use the existing speed correction factors and methodology found in

MOBILE5 for diesel vehicles, gasoline fueled heavy-duty vehicles and motorcycles. Heavy-duty

diesel vehicles will also be adjusted for NOx excess emissions separately from the MOBILE6

speed correction factors. 
DRAFT M6.SPD.002h 23 August 24, 1999

In MOBILE6, the daily average emission rate will be calculated by VMT weighting an

emission estimate for each hour of the day. Within each hour of the day, there will be a

distribution of speeds for freeways and arterial/collectors, either a default national average or a

user supplied distribution. The speed correction would be applied to the estimate of Normal and

High emitters within each model year separately. Older (pre-1981) model year gasoline fueled,

light-duty vehicles will have only composite (combined Normal and High) basic exhaust

emission rates. In these cases the speed correction will be applied to the composite basic exhaust

emission rates (including both Normal and High emitters). Speed correction factors will not be

applied to the effects of engine start on emissions estimated by MOBILE6.

The speed distribution in MOBILE6 will consist of average speed “bins” from 5 to 65

mph in 5 mph increments and for 2.5 mph (14 speed bins) representing the distribution of

average speeds within each hour. Each hour of the day will have an estimate of the distribution

of vehicle miles traveled (VMT) on freeways, ramps, local and arterial/collector roadways. 

These distributions will be used to weight together the emission estimates in each speed bin to

give an hourly emission estimate. Freeway Ramps and Local Roadways will have hourly

emission estimates and VMT estimates, but will not have speed distributions. The hourly

emission estimates will be weighted by the hourly VMT distribution separately for each facility. 

Finally, the VMT distribution between facilities will be used to combine the results into an areawide running exhaust emission estimate. Emissions due to engine start within each hour will be

calculated separately. In summary, MOBILE6 will:

o Determine the basic running exhaust emission rate (BER).

o For each hour, correct the BER for temperature and fuel effects.

o Using the corrected BER, calculate the emissions for Freeway Ramps, Local

Roadways and for the 14 speed bins for freeways and arterial/collectors using the

appropriate emission offsets and speed correction factors described in this

document.

o Using the speed distributions, weight the freeways, ramps, local and

arterial/collector speed bin results to get hourly emissions.

o Using the hourly VMT distributions, weight together the hourly facility results to

get daily emissions by facility.

o Using the facility VMT distribution, weight the daily facility emissions to get the

area-wide running exhaust emission estimate.

o Combine the running exhaust emission estimate with the engine start emissions to

get the composite exhaust emission rate.

Appendix B shows an example calculation.

The national average default factors proposed to be used in MOBILE6 for VMT

weighting the speed-corrected, facility-type emissions into a single area-wide running emissions

rate is described in a report prepared for EPA by Systems Applications International3

. This

report also contains the default distributions of average speeds on each facility over the day. All
DRAFT M6.SPD.002h 24 August 24, 1999

of these default values can be overridden by the user with local information using methods

described in a separate guidance document4

.

The operating mode inputs used in MOBILE5 will not be needed for MOBILE6. Instead,

MOBILE6 uses values for the number of engine starts, the distribution of soak times between

engine starts, the mileage accumulation rates and the distribution of these factors over the day5

. 

These values are used to determine the weighting of the running exhaust emissions with the

effects of engine starts to calculate a composite exhaust emission factor. Although MOBILE6

contains default values, these default values will normally be overridden by user supplied local

information.

Similarly, once the composite running and engine start emissions are calculated, the

composite exhaust HC emissions can be combined with the calculated non-exhaust HC

emissions. The reader should refer to the reports regarding the non-exhaust emission estimates

and their associated activity for more details on how these values are calculated.

7.0 COMPARISON TO MOBILE5

Figures 6a, 6b, and 6c show the proposed MOBILE6 speed correction factors (SCFs) for

freeways compared to selected speed correction factors used in MOBILE5. This comparison

cannot be made clearly, since the two versions of the model use very different approaches. 

 The proposed MOBILE6 SCFs depend on emission level and the MOBILE5 SCFs

do not.

 The MOBILE5 SCFs are applied to a composite exhaust emission rate, including

engine start emissions. The MOBILE6 SCFs will only be applied to the hot

running exhaust emissions, before the effects of engine start are added.

 The MOBILE6 SCFs are intended to estimate the effects on freeways excluding

ramp activity, but the MOBILE5 SCFs are a composite of all roadway types.

 The MOBILE6 SCFs include the effect of additional aggressive driving effects on

emissions missing from the MOBILE5 SCFs.

The overall shape of the MOBILE5 and MOBILE6 SCFs is similar. The MOBILE6

SCFs are flatter at speeds greater than 55 mph than in MOBILE5, especially for CO and NOx. 

This may be due largely to the fact that the old speed cycles above 48 mph all started from idle

(zero mph) and accelerated to a speed higher than the average speed of the cycle. This extra

acceleration, which is not generally found on cruising vehicles on limited access freeways, adds

to the power demand, therefore likely increasing emissions in the old high speed cycles relative

to lower speed cycles. The acceleration to reach freeway speeds is now contained in the separate

ramp cycle. This additional ramp cycle will allow this effect to be weighted appropriately with

freeway driving. The effect from starting and ending at idle is less pronounced in the lower

speed cycles since they inherently have a higher percentage of driving at idle.
DRAFT M6.SPD.002h 25 August 24, 1999

In Figure 6a (THC), the MOBILE6 SCF for the lowest emission level (based Tier 1

vehicles) has a positive slope beyond about 30 mph, indicating increasing THC emissions with

increasing average speed. However, as shown in Figure 4a, Tier 1 vehicles are much cleaner at

all speeds than the normal emitting Tier 0 vehicles. The shape of the THC MOBILE6 SCFs for

the higher emission levels (based on Tier 0 vehicles, Normal and High) is very close to the shape

of MOBILE5 SCFs.

 For higher average speeds (above 19.6 mph) the proposed MOBILE6 SCFs for CO

emissions (Figure 6b) have a strongly positive slope at lower emission levels (based on Tier 0

Normals and Tier 1 vehicles). This is very different from the SCFs used in MOBILE5. The

proposed MOBILE6 SCFs for THC/NMHC emissions for Tier 0 Normal vehicles have a negative

slope. However CO emissions are more sensitive to aggressive driving than THC/NMHC

emissions, which may explain the difference in the trends.

The proposed MOBILE6 SCFs for NOx emissions (Figure 6c) for the higher emission

levels (based on Tier 0 vehicles) have a slight upward trend at higher speeds, similar to the

MOBILE5 trends. The lowest emission level SCFs (based on Tier 1 vehicles) has a steep slope,

similar to the oldest MOBILE5 SCF. All of the proposed MOBILE6 SCFs tend to rise as average

speeds decrease, which is expected with more accelerations and decelerations (stop and go

driving) present in the driving patterns. However, the MOBILE6 SCFs rise much more steeply

and to higher levels than the MOBILE5 SCFs.

Since the Freeway Ramp and Local Roadway emissions are estimated directly from the

basic exhaust emission rate (based on the hot running LA4 emissions), they cannot be compared

to the speed correction factor used in MOBILE5. When MOBILE6 is nearer completion, it will

be possible to create a composite result containing a weighted sum of all of the roadway types in

MOBILE6 that can be more fairly compared to MOBILE5 results.

8.0 COMMENTS

EPA is requesting that MOBILE model stakeholders and other knowledgeable readers

comment on the methodology and validity of the assumptions used to determine the speed

correction factors proposed in this document. Comments should clearly distinguish between

recommendations for clearly defined improvements that can be readily made in the short term

based on data reasonably at hand to EPA and improvements that are long term, exploratory or

dependent on data not currently available to EPA. The schedule for MOBILE6 will not allow for

the serious consideration of proposed long term improvements. However, these long term

comments will be considered for future data collection and data analysis. General areas for

review include:

 Report clarity;

 Overall methodology

 Appropriateness of data sets selected;
DRAFT M6.SPD.002h 26 August 24, 1999

 Statistical approaches used;

 Empirical relationships selected;

 Appropriateness of the conclusions;

 Recommendations for alternate data sources or methods.

Comments on this report and its proposed use in MOBILE6 may be submitted

electronically to:

mobile@epa.gov

or by fax to:

(734) 214-4939

or by mail to:

MOBILE6 Review Comments

2000 Traverwood

US EPA Assessment and Modeling Division

Ann Arbor MI 48105

Electronic submission of comments is preferred. All comments may be made public. In

your comments, please note clearly the document that you are commenting on. Please be sure to

include your name, address, affiliation, and any other pertinent information.
DRAFT M6.SPD.002h 27 August 24, 1999

References

1. Carlson, T.R., et al., “Development of Speed Correction Cycles,” MOBILE6 Stakeholder

Review Document (M6.SPD.001). Prepared for EPA by Sierra Research, Inc., 1997.

2. Brzezinski, D.J., et al., “Coefficients for the Determination of Engine Start and Running

Emissions From FTP Bag Emissions,” MOBILE6 Stakeholder Review Document

(M6.STE.002), 1997.

3. “Development of Methodology for Estimating VMT Weighting by Facility Type,” 

MOBILE6 Stakeholder Review Document (M6.SPD.003) EPA420-P-99-006. Prepared

for EPA by Systems Applications International, Inc., 1998.

4. “Guidance for the Development of Facility Type VMT and Speed Distributions,”

MOBILE6 Stakeholder Review Document (M6.SPD.004) EPA420-P-99-004. Prepared

for EPA by Systems Applications International, Inc., 1998.

5. Glover, E.L., et al., “Soak Length Activity Factors for Start Emissions,” MOBILE6

Stakeholder Review Document (M6.FLT.003),
DRAFT M6.SPD.002h 28 August 24, 1999

Tables
DRAFT M6.SPD.002h 29 August 24, 1999

Table 1

New Facility-Specific/Area-Wide Speed Correction Cycle

Statistics

Cycle*

Average

Speed

(mph)

Maximum

Speed

(mph)

Maximum

Accel Rate

(mph/s)

Length

(seconds)

Length

(miles)

Freeway, High Speed 63.2 74.7 2.7 610 10.72

Freeway, LOS A-C 59.7 73.1 3.4 516 8.55

Freeway, LOS D 52.9 70.6 2.3 406 5.96

Freeway, LOS E 30.5 63.0 5.3 456 3.86

Freeway, LOS F 18.6 49.9 6.9 442 2.29

Freeway, LOS “G” 13.1 35.7 3.8 390 1.42

Freeway Ramps 34.6 60.2 5.7 266 2.56

Arterial/Collectors

LOS A-B

24.8 58.9 5.0 737 5.07

Arterial/Collectors

LOS C-D

19.2 49.5 5.7 629 3.36

Arterial/Collectors

LOS E-F

11.6 39.9 5.8 504 1.62

Local Roadways 12.9 38.3 3.7 525 1.87

Non-Freeway AreaWide Urban Travel19.4 52.3 6.4 1,348 7.25

* LOS (level of service) refers to roadway congestion categories. See Section 4.6.
DRAFT M6.SPD.002h 30 August 24, 1999

Table 2

Comparison of Key Representativeness Statistics

For Facility-Specific Cycle Schedules

Versus Total Vehicle Observations

Driving Cycle

Mean

Speed

(mph)

Maximum

Speed

(mph)

Maximum

Accel Rate

(mph/sec)

Total

SAFD

Difference

(%)

High-Power

Difference

(%) Cyc. Obs. Cyc. Obs. Cyc. Obs.

Freeway High-Speed 63.2 62.7 74.7 80.9 2.7 5.8 9.41 0.16

Freeway LOS A-C 59.7 59.2 73.1 83.2 3.4 6.8 12.12 0.39

Freeway LOS D 52.9 52.0 70.6 75.8 2.3 6.1 15.10 0.35

Freeway LOS E 30.5 32.1 63.0 71.3 5.3 8.5 25.17 0.18

Freeway LOS F 18.6 19.9 49.9 69.5 6.9 9.6 23.83 0.06

Freeway LOS G 13.1 14.4 35.7 49.1 3.8 5.7 18.80 0.10

Freeway Ramp 34.6 35.4 60.2 79.1 5.7 9.3 42.74 0.99

Arterial LOS A-B 24.8 25.2 58.9 74.9 5.0 14.9 17.04 0.40

Arterial LOS C-D 19.2 18.9 49.5 71.3 5.7 10.4 16.86 0.21

Arterial LOS E-F 11.6 12.0 39.9 56.8 5.8 10.2 17.86 0.24

Local Roadways 12.8 14.6 38.3 62.7 3.7 12.5 21.80 0.11

Unified Cycle 24.6 26.3 67.2 80.3 6.9 10.4 30.27 0.19
DRAFT M6.SPD.002h 31 August 24, 1999

Table 3

Statistics for Additional Tested Cycles

Cycle

Average

Speed

(mph)

Maximum

Speed

(mph)

Maximum

Accel Rate

(mph/s)

Length

(seconds)

Length

(miles)

LA4

(Urban Dynamometer

Driving Cycle)

19.6 56.7 3.3 1368 7.45

Running 505

(First 505 seconds of the

Urban Dynamometer

Driving Cycle)

25.6 56.7 3.3 505 3.59

Unified Cycle (LA92) 24.6 67.2 6.9 1435 9.81

ST01

(Engine Start Cycle)

20.2 41.0 5.1 248 1.39

New York City Cycle

(NYCC)

7.1 27.7 6.0 600 1.18

Table 4

Distribution of the Vehicle Sample

By Emission Standard and Technology

Fuel Delivery

TIER 0 Emission

Standard

TIER 1 Emission

Standard

Total

Sample

Carburetor 7 -- 7

Throttle Body FI 27 1 28

Multi-Port FI 39 11 50

Total Sample 73 12 85
DRAFT M6.SPD.002h 32 August 24, 1999

Table 5

Vehicle Sample Description

Site

Veh. 

No.

Veh. 

Class VIN

Mod.

Yr. Make Mod. Std. Miles

Eng.

Size

Fuel

Inj. IM240

E.LIB 5001 LDV 1G4AH51R7J6401871 88 BUICK CENT Tier 0 129,698 2.5 TBI PASS

E.LIB 5002 LDV 1G3NL54UXKM283722 89 OLDSMOBILE CUTL Tier 0 61,956 2.5 TBI FAIL

E.LIB 5003 LDV 2FACP74F3MX162914 91 FORD CROW Tier 0 53,003 5.0 PFI PASS

E.LIB 5005 LDV 1G1JC14GOM7126454 91 CHEVROLET CAVA Tier 0 54,658 2.2 TBI PASS

E.LIB 5006 LDV 1G1JC111XK7150483 89 CHEVROLET CAVA Tier 0 107,611 2.0 TBI PASS

E.LIB 5007 LDV 1G3HY54C9JW312653 88 OLDSMOBILE DELT Tier 0 101,534 3.8 PFI PASS

E.LIB 5008 LDV 1FACP57U5NG145893 92 FORD TAUR Tier 0 74,078 3.0 PFI PASS

E.LIB 5009 LDV 1G2WP14T6KF307905 89 PONTIAC GRAN Tier 0 155,181 3.1 PFI FAIL

E.LIB 5010 LDV 4T1SK12E9PU184046 93 TOYOTA CAMR Tier 0 29,392 2.2 TBI PASS

E.LIB 5011 LDV 2C1MS2468P6704533 93 GEO METR Tier 0 105,445 1.0 TBI PASS

E.LIB 5012 LDV 1G2NV54D9JC821314 88 PONTIAC GRAN Tier 0 89,764 2.3 TBI PASS

E.LIB 5013 LDV 1G2NE5434PC795009 93 PONTIAC GRAN Tier 0 72,348 2.3 PFI PASS

E.LIB 5014 LDV 1G6CD53B7M4272204 91 CADILLAC SEDA Tier 0 51,707 4.9 TBI FAIL

E.LIB 5015 LDV 1G2NE5438PC758996 93 PONTIAC GRAN Tier 0 58,538 2.3 PFI PASS

E.LIB 5016 LDV 1G4HR54C5KH488839 89 BUICK LESA Tier 0 65,212 3.8 TBI FAIL

E.LIB 5017 LDV WVWEB5159MK012875 91 VW CABR Tier 0 67,496 1.8 TBI PASS

E.LIB 5018 LDV 1B3ES27C9SD221573 95 DODGE NEON Tier 1 20,855 2.0 TBI PASS

E.LIB 5019 LDV 1G1FP23TXLL111092 90 CHEVROLET CAMA Tier 0 71,258 3.1 PFI FAIL

E.LIB 5020 LDV 1FACP5245NG196687 92 FORD TAUR Tier 0 84,148 3.8 TBI PASS

E.LIB 5021 LDV 1B3ES67C2SD188892 95 DODGE NEON Tier 1 28,525 2.0 PFI PASS

E.LIB 5022 LDV 1G1JC1112KJ207455 89 CHEVROLET CAVA Tier 0 110,929 2.0 TBI PASS

E.LIB 5023 LDV 1FAPP36X6JK249611 88 FORD TEMP Tier 0 107,979 2.3 PFI PASS

E.LIB 5024 LDV 2FAPP36X8MB116542 91 FORD TEMP Tier 0 97,522 2.3 PFI FAIL

E.LIB 5025 LDT1 1N6SD16S6MC351945 91 NISSAN HARD Tier 0 103,346 2.4 PFI PASS

E.LIB 5026 LDV 1MEBM50U3KG663746 89 MERCURY SABL Tier 0 107,075 3.0 PFI FAIL

E.LIB 5027 LDV JE3CU14A1NU003588 92 EAGLE SUMM Tier 0 129,457 1.5 PFI FAIL

E.LIB 5028 LDV 1YVGE22A8P5138202 93 MAZDA 626 Tier 0 103,171 12 PFI FAIL

E.LIB 5029 LDT1 1P4FH4430KX568849 89 PLYMOUTH VOYA Tier 0 118,586 3.0 PFI PASS

E.LIB 5030 LDV 1FABP29D9GA165884 86 FORD TAUR Tier 0 50,755 2.5 TBI FAIL

E.LIB 5031 LDV JT2SV24E8J3189405 88 TOYOTA CAMR Tier 0 197,090 2.0 PFI FAIL

E.LIB 5032 LDV 1MEBP923XFA603099 85 MERCURY COUG Tier 0 113,584 14 TBI FAIL

E.LIB 5033 LDT1 1GCBS14E3H2170996 87 CHEVROLET S10 Tier 0 128,681 2.5 TBI PASS

E.LIB 5034 LDT1 1GCBS14A3F2156946 85 CHEVROLET S10 Tier 0 89,435 1.9 NO PASS

E.LIB 5035 LDV 1FABP37X6HK239681 87 FORD TEMP Tier 0 118,148 2.5 TBI FAIL

E.LIB 5036 LDV JN1HM05S8HX081093 87 NISSAN STAN Tier 0 58,173 2.0 PFI PASS

E.LIB 5037 LDV 1P3BP49CXDF305484 83 PLYMOUTH RELI Tier 0 94,399 2.2 NO FAIL

E.LIB 5038 LDV 2G1WL52M2T9212643 96 CHEVROLET LUMI Tier 1 16,557 3.1 PFI PASS

E.LIB 5039 LDV 1HGED3554JA017137 88 HONDA CIVI Tier 0 184,457 1.5 TBI FAIL

E.LIB 5040 LDV 2HGED6359KH534893 89 HONDA CIVI Tier 0 161,598 12 TBI PASS

E.LIB 5041 LDV JT2EL32G3H0076681 87 TOYOTA TERC Tier 0 136,654 1.5 NO PASS

E.LIB 5042 LDT1 1GCDM15NXFB180388 85 CHEVROLET ASTR Tier 0 179,855 4.3 NO FAIL

E.LIB 5043 LDV 2HGED6349KH537915 89 HONDA CIVI Tier 0 122,821 1.5 TBI PASS

E.LIB 5044 LDT1 1GTBS14E5J2520442 88 CHEVROLET S15 Tier 0 115,693 2.5 TBI FAIL
Table 5

Vehicle Sample Description

DRAFT M6.SPD.002h 33 August 24, 1999

E.LIB 5045 LDV 1G2WH54T6PF250844 93 PONTIAC GRAN Tier 0 85,789 3.4 PFI FAIL

E.LIB 5046 LDT1 1FTCR1056FUD20466 85 FORD RANG Tier 0 56,488 2.8 NO FAIL

E.LIB 5047 LDT1 1FTDE14N8MHB05052 91 FORD ECON Tier 0 79,573 5.8 PFI FAIL

E.LIB 5048 LDT1 1FTCR10A2KUB93426 89 FORD RANG Tier 0 123,419 2.3 TBI PASS

E.LIB 5049 LDV 2G1AW19X5G1258479 86 CHEVROLET CELE Tier 0 131,601 2.8 NO PASS

E.LIB 5050 LDT1 1FDDE14F9FHA59240 85 FORD ECON Tier 0 86,203 5.8 NO PASS

E.LIB 5051 LDV 1G1JF11W1K7156403 89 CHEVROLET CAVA Tier 0 123,581 3.1 PFI PASS

E.LIB 5052 LDV 1G1JC14GXM7146551 91 CHEVROLET CAVA Tier 0 90,945 2.2 TBI PASS

E.LIB 5053 LDT2 1FDEE14N0MHB15171 91 FORD E150 Tier 0 97,531 5.8 PFI FAIL

E.LIB 5054 LDV 1FAPP1282MW314230 91 FORD ESCO Tier 0 105,861 1.8 PFI FAIL

E.LIB 5055 LDT1 2P4GH25K6MR240965 91 PLYMOUTH VOYA Tier 0 72,032 2.5 TBI PASS

E.LIB 5056 LDT1 1GNDM15Z4MB190115 91 CHEVROLET ASTR Tier 0 90,880 4.3 TBI PASS

E.LIB 5057 LDV 1G1LT53T9PY237873 93 CHEVROLET CORS Tier 0 41,766 3.4 PFI PASS

E.LIB 5058 LDT1 1GCCS19Z5P0178401 93 CHEVROLET S10 Tier 0 48,578 4.3 TBI PASS

E.LIB 5059 LDV 4T1SK11E4PU252562 93 TOYOTA CAMR Tier 0 67,344 2.2 PFI PASS

E.LIB 5060 LDV 1HGCB7658PA075439 93 HONDA ACCO Tier 0 61,163 2.2 PFI PASS

E.LIB 5061 LDV JN1HJ01P0LT397615 90 NISSAN MAXI Tier 0 120,786 3.0 PFI PASS

E.LIB 5062 LDV JE3CA11A7PU098450 93 EAGLE SUMM Tier 0 52,447 1.5 PFI PASS

E.LIB 5063 LDV 1G2WJ52M7TF204255 96 PONTIAC GRAN Tier 1 20,451 3.1 PFI PASS

AA 5213 LDV JT2AE94A5N0273089 92 TOYOTA CORO Tier 0 77,310 1.6 PFI NULL

AA 5217 LDV 1HGCD5632TA260884 96 HONDA ACCO Tier 1 7,573 2.2 PFI NULL

AA 5218 LDV 1G8ZF5498NZ175489 92 SATURN SL Tier 0 89,995 1.9 TBI NULL

AA 5219 LDV 1G1LW13T4NY109988 92 CHEVROLET BERR Tier 0 94,316 3.1 PFI NULL

AA 5220 LDT2 1FTEF14N3RLB27661 94 FORD F150 Tier 0 97,629 5.8 PFI NULL

AA 5221 LDT2 1FTEF1549TLB25543 96 FORD F150 Tier 1 12,877 4.9 PFI NULL

AA 5222 LDV JM1BG2263N0464490 92 MAZDA PROT Tier 0 10,727 1.8 PFI NULL

AA 5223 LDV 2G1WL52M2T9212643 96 CHEVROLET LUMI Tier 1 17,233 3.1 PFI NULL

AA 5224 LDV 1G1JC5447N7116728 92 CHEVROLET CAVA Tier 0 90,196 2.2 PFI NULL

AA 5225 LDT1 1FTCR10A9TPB08548 96 FORD RANG Tier 1 10,064 2.3 PFI NULL

AA 5227 LDT2 1GNEV16K9LF116974 90 CHEVROLET SURB Tier 0 97,658 5.7 TBI NULL

AA 5228 LDV 2C3ED56F7RH211101 94 CHRYSLER LHS Tier 0 59,937 3.5 PFI NULL

AA 5229 LDV 1HGEJ8142TL073569 96 HONDA CIVI Tier 1 9,433 1.6 PFI NULL

AA 5230 LDT1 1GNDM19WXRB229457 94 CHEVROLET ASTR Tier 0 77,178 4.3 PFI NULL

AA 5231 LDV 1G8ZK5570RZ145840 94 SATURN SL Tier 0 25,930 1.9 PFI NULL

AA 5232 LDV KMHJF22M5RU669848 94 HYUNDAI ELAN Tier 0 57,960 1.8 PFI NULL

AA 5233 LDT1 1GNDU06D3NT126706 92 CHEVROLET LUMI Tier 0 33,872 3.1 PFI NULL

AA 5234 LDV 1FARP15J9RW262996 94 FORD ESCO Tier 1 51,168 1.9 PFI NULL

AA 5235 LDT1 2P4FH5532LR534285 90 PLYMOUTH VOYA Tier 0 98,530 3.0 PFI NULL

AA 5237 LDV 2G1WN54X7N9117726 92 CHEVROLET LUMI Tier 0 16,133 3.4 PFI NULL

AA 5239 LDT1 1GMDU06LXRT234029 94 PONTIAC TRAN Tier 1 68,305 3.8 PFI NULL

AA 5240 LDV 4T1BF12K3TU871236 96 TOYOTA CAMR Tier 1 18,992 3.0 PFI NULL

AA 5241 LDV 1B3XC56R3LD749334 90 DODGE DYNA Tier 0 6,813 3.3 PFI NULL
DRAFT M6.SPD.002h 34 August 24, 1999

Table 6

Distribution of Vehicle Sample

By Vehicle Class and Model Year

Model Year

Passenger

Car

Light-Duty Truck

(0-6000 GVW)

Light-Duty Truck

(6000-8500 GVW) Total

1983 1 -- -- 1

1985 1 4 -- 5

1986 2 -- -- 2

1987 3 1 -- 4

1988 6 1 -- 7

1989 9 2 -- 11

1990 3 1 1 5

1991 7 4 1 12

1992 9 1 -- 10

1993 10 1 -- 11

1994 4 2 1 7

1995 2 -- -- 2

1996 6 1 1 8

TOTAL 63 18 4 85
DRAFT M6.SPD.002h 35 August 24, 1999

Table 7a

Facility-Specific/Area-Wide Speed Correction Cycles Test Results

Total Hydrocarbons (THC)

Cycle

Normal Emitters High Emitters

N Mean

(g/mile) 

STD N Mean

(g/mile)

STD

Freeway at 63.2 mph 61 0.15 0.19 24 1.80 1.66

Freeway at 59.7 mph 61 0.16 0.17 24 1.77 1.69

Freeway at 52.9 mph 61 0.14 0.17 24 1.70 1.38

Freeway at 30.5 mph 61 0.21 0.26 24 2.52 2.12

Freeway at 18.6 mph 61 0.25 0.30 24 3.67 3.75

Freeway at 13.1 mph 61 0.27 0.33 24 4.13 4.06

Freeway Ramps (34.6 mph) 61 0.34 0.46 24 3.04 2.21

Arterial/Collectors

at 24.8 mph

61 0.22 0.26 24 3.03 3.07

Arterial/Collectors

at 19.2 mph

61 0.26 0.32 24 3.97 4.79

Arterial/Collectors

at 11.6 mph

61 0.45 0.84 24 5.15 5.63

Local Roadways (12.9 mph) 61 0.28 0.34 24 4.48 5.07

Non-Freeway Area-Wide

Urban Travel (19.4 mph)

60* 0.26 0.31 24 3.57 3.06

FTP (19.6 mph) 61 0.38 0.27 24 3.49 2.77

Running 505 (25.6 mph) 61 0.17 0.23 24 2.57 2.51

Unified Cycle (24.6 mph) 60* 0.24 0.27 24 3.16 3.33

ST01(20.2 mph) 61 2.32 2.29 23* 6.88 5.36

NYCC (7.1 mph) 61 0.62 1.09 24 7.31 7.82

* Test not done
DRAFT M6.SPD.002h 36 August 24, 1999

Table 7b

Facility-Specific/Area-Wide Speed Correction Cycles Test Results

Carbon Monoxide (CO)

Cycle

Normal Emitters High Emitters

N Mean

(g/mile) 

STD N Mean

(g/mile)

STD

Freeway at 63.2 mph 70 6.96 7.71 15 66.76 52.09

Freeway at 59.7 mph 70 6.96 6.12 15 65.63 54.63

Freeway at 52.9 mph 70 5.53 5.33 15 54.45 41.82

Freeway at 30.5 mph 70 4.48 4.01 15 66.38 43.18

Freeway at 18.6 mph 70 5.19 4.90 15 74.39 63.48

Freeway at 13.1 mph 70 4.79 4.45 15 82.09 77.01

Freeway Ramps (34.6 mph) 70 10.06 10.79 15 84.02 57.32

Arterial/Collectors

at 24.8 mph

70 4.28 3.87 15 75.24 59.12

Arterial/Collectors

at 19.2 mph

70 5.22 5.01 15 80.79 62.65

Arterial/Collectors

at 11.6 mph

70 5.94 5.65 15 116.57 94.9

Local Roadways (12.9 mph) 70 4.23 4.14 15 92.41 87.81

Non-Freeway Area-Wide

Urban Travel (19.4 mph)

69* 4.80 4.62 15 86.63 62.32

FTP (19.6 mph) 70 5.05 3.70 15 79.92 56.89

Running 505 (25.6 mph) 70 3.04 2.75 15 74.04 57.5

Unified Cycle (24.6 mph) 69* 5.93 5.34 15 77.94 58.19

ST01 (20.2 mph) 70 24.55 16.54 14* 111.2 70.30

NYCC (7.1 mph) 70 7.88 8.12 15 158.04 136.34

* Test not done
DRAFT M6.SPD.002h 37 August 24, 1999

Table 7c

Facility-Specific/Area-Wide Speed Correction Cycles Test Results

Nitrogen Oxides (NOx)

Cycle

Normal Emitters High Emitters

N Mean

(g/mile) 

STD N Mean

(g/mile)

STD

Freeway at 63.2 mph 72 0.77 0.71 13 3.35 1.07

Freeway at 59.7 mph 72 0.74 0.65 13 3.27 1.02

Freeway at 52.9 mph 72 0.70 0.60 13 3.20 0.97

Freeway at 30.5 mph 72 0.63 0.54 13 3.15 1.00

Freeway at 18.6 mph 72 0.72 0.59 13 3.73 1.34

Freeway at 13.1 mph 72 0.51 0.39 13 2.81 0.99

Freeway Ramps (34.6 mph) 72 0.98 0.81 13 4.00 1.43

Arterial/Collectors

at 24.8 mph

72 0.68 0.55 13 3.47 1.07

Arterial/Collectors

at 19.2 mph

72 0.79 0.66 13 3.77 1.46

Arterial/Collectors

at 11.6 mph

72 0.96 0.78 13 4.44 1.84

Local Roadways (12.9 mph) 72 0.73 0.63 13 3.74 1.46

Non-Freeway Area-Wide

Urban Travel (19.4 mph)

71* 0.71 0.57 13 3.56 1.18

FTP (19.6 mph) 72 0.70 0.53 13 3.25 1.04

Running 505 (25.6 mph) 72 0.59 0.50 13 3.67 1.13

Unified Cycle (24.6 mph) 71* 0.84 0.66 13 3.83 1.23

ST01 (20.2 mph) 72 1.85 1.11 12* 3.78 1.34

NYCC (7.1 mph) 72 0.95 0.69 13 4.07 1.45

* Test not done
DRAFT M6.SPD.002h 38 August 24, 1999

Table 8

Analysis of Variance Results (ANOVA P-Values)

Factor* THC CO NOx NMHC

All Roadways Speed 0.0000 0.0000 0.0000 0.0001

Emitter Class 0.0000 0.0000 0.0000 0.0000

Speed*Emitter Class 0.1411 0.0152 0.9894 0.1271

========================= Normal Emitters =========================

Factor* THC CO NOx NMHC

Arterial/Collector

and Freeway

Roadway Type** 0.0046 0.0006 0.0000 0.0050

Speed*Roadway Type** 0.0354 0.0020 0.0000 0.0440

Vehicle Class 0.0016 0.0031 0.0012 0.0404

Speed*Vehicle Class 0.1754 0.8680 0.5723 0.1802

Standard*** 0.0000 0.0000 0.0000 0.0000

Speed*Standard*** 0.0002 0.0576 0.6491 0.0001

Local Roadway Vehicle Class 0.0830 0.4038 0.0124 0.5008

Standard*** 0.0000 0.0000 0.0028 0.0000

Freeway Ramp Vehicle Class 0.2922 0.0443 0.0018 0.7707

Standard*** 0.0003 0.0002 0.0000 0.0007

========================= High Emitters =========================

Factor* THC CO NOx NMHC

Arterial/Collector

and Freeway

Roadway Type** 0.1236 0.3307 0.0000 0.1307

Speed*Roadway Type** 0.1176 0.6233 0.0000 0.1203

Vehicle Class 0.5942 0.8984 0.3961 0.5693

Speed*Vehicle Class 0.0641 0.0241 0.9560 0.0699

Local Roadway Vehicle Class 0.8787 0.5511 0.6093 0.8821

Freeway Ramp Vehicle Class 0.3701 0.1471 0.6942 0.4075

 * All emissions in Log (gram/hour) space.

 ** Freeways versus Arterial/Collectors limited to speeds < 30 mph, including a

vehicle term.

 *** There are no Tier 1 High emitters in sample. Some low emitting Tier 0 vehicles

are considered both as Tier 0 and as Tier 1 vehicles (see text). 
DRAFT M6.SPD.002h 39 August 24, 1999

Table 8

Analyses of Variance Results (ANOVA p values)

Factor* THC NMHC CO NOx

Emitter Level .0000 .0000 .0000 .0000

Normal Emitters Only

Roadway type** .0006 .0003 .0206 .0000

Vehicle Class .0001 .0004 .0001 .0001

Standard*** .0001 .0001 .0001 .0001

Local/Vehicle Class .0476 .1490 .0325 .2753

Local/Standard .0001 .0001 .0001 .0001

Ramp/Vehicle Class .0396 .0983 .0107 .0871

Ramp/Standard .0001 .0001 .0001 .0001

High Emitters Only

Roadway type** .3094 .3281 .0318 .0000

Vehicle Class .067 .067 .0004 .144

Standard*** NA NA NA NA

 * All emissions in Log (gram/hour) space.

 ** Freeways versus Arterial/Collectors limited to speeds < 30 mph, including a

vehicle term.

 *** There were no Tier 1 High emitters in sample. Some low emitting Tier 0 vehicles

were considered both as Tier 0 and as Tier 1 vehicles (see text). 
DRAFT M6.SPD.002h 40 August 24, 1999

Table 9

Description of Sample Vehicles Used for Tier 1 Analysis

Veh

No.

Test

Site

Tier

Std. Mileage

FTP

NMHC

FTP

NOx

Veh

Class

Model

Yr.

Eng.

Size

Fuel

Inj.

IM240

Status VIN

5007 E.LIB 0 101536 0.13 0.23 LDV 88 3.80 PFI PASS 1G3HY5C9JW312653

5010 E.LIB 0 29392 0.12 0.21 LDV 93 2.20 TBI PASS 4T1SK12E9PU18406

5013 E.LIB 0 72348 0.08 0.18 LDV 93 2.30 PFI PASS 1G2NE5438PC758996

5015 E.LIB 0 58538 0.07 0.41 LDV 93 2.30 PFI PASS 1G2NE5438PC758996

5017 E.LIB 0 67496 0.15 0.13 LDV 91 1.80 TBI PASS WVWEB5159MK012875

5018 E.LIB 1 20855 0.12 0.10 LDV 95 2.00 TBI PASS 1B3ES27C9SD221573

5021 E.LIB 1 28525 0.12 0.10 LDV 95 2.00 PFI PASS 1B3ES67C2SD188892

5038 E.LIB 1 16557 0.12 0.34 LDV 96 3.10 PFI PASS 2GIWL52M2T9212643

5059 E.LIB 0 6734 0.13 0.28 LDV 93 2.20 PFI PASS 4T1SK11E4PU252562

5060 E.LIB 0 61163 0.11 0.27 LDV 93 2.20 PFI PASS 1HGCB7658PA075439

5063 E.LIB 1 20451 0.16 0.26 LDV 96 3.10 PFI PASS 1G2WJ52M7TF204255

5217 AA 1 7573 0.09 0.20 LDV 96 2.20 PFI NULL 1HGCD5632TA260884

5218 AA 0 89995 0.19 0.39 LDV 92 1.90 PFI NULL 1G8ZF5498NZI75489

5221 AA 1 12877 0.10 0.53 LDT2 96 4.90 PFI NULL 1TEF1549TLB25543

5223 AA 1 17233 0.21 0.49 LDV 96 3.10 PFI NULL 2G1WL52M2T9212643

5225 AA 1 10064 0.12 0.40 LDT1 96 2.20 PFI NULL 1FTCR10A9TPB08548

5229 AA 1 9433 0.17 0.10 LDV 96 1.60 PFI NULL 1HGEJ8142TL073569

5234 AA 1 51168 0.15 0.26 LDV 94 1.90 PFI NULL 1FARP15J9RW262996

5239 AA 1 68305 0.19 0.71 LDT1 94 3.80 PFI NULL 1GMDU06LXRT234029

5240 AA 1 18992 0.21 0.31 LDV 96 3.00 PFI NULL 4T1BF12K3TU871236
DRAFT M6.SPD.002h 41 August 24, 1999

Table 10

Tests of Convergence in Arterial and Freeway Estimates at 30 mph

Tier 0 Normal Emitter Sample

Parameter Estimate

T for H0:

Parameter = 0

p value

Pr > | T |

Standard Error

of the Estimate

THC 0.18089092 1.84 0.0670 0.09840365

NMHC 0.15532642 1.83 0.0688 0.08503405

CO 1.63652794 2.96 0.0033 0.55229111

NOx 0.05946957 1.24 0.2160 0.04797825

Tier 0 High Emitter Sample

Parameter Estimate

T for H0:

Parameter = 0

p value

Pr > | T |

Standard Error

of the Estimate

THC 0.95357931 1.52 0.1304 0.62676490

NMHC 0.84766279 1.58 0.1161 0.53612496

CO 24.7784634 1.48 0.1430 16.7645083

NOx -0.00945343 -0.04 0.9705 0.25464544

Tier 1 Normal Emitter Sample

Parameter Estimate

T for H0:

Parameter = 0

p value

Pr > | T |

Standard Error

of the Estimate

THC 0.01509669 1.15 0.2534 0.01310665

NMHC 0.00615421 0.71 0.4813 0.00869272

CO 0.25453921 0.83 0.4114 0.30796933

NOx 0.04101364 1.20 0.2350 0.03423678
DRAFT M6.SPD.002h 42 August 24, 1999

Table 11a

Average Emissions by Emission Standard and Emission Level

Total Hydrocarbons (THC)

Cycle

Tier 1* Tier 0 Normal Tier 0 High

N

Mean

(g/mi)

Std.

Dev. N

Mean

(g/mi)

Std.

Dev. N

Mean

(g/mi)

Std.

Dev.

Freeway at 63.2 mph 20 0.050 0.032 49 0.183 0.200 24 1.798 1.656

Freeway at 59.7 mph 20 0.066 0.038 49 0.187 0.180 24 1.771 1.688

Freeway at 52.9 mph 20 0.035 0.019 49 0.171 0.178 24 1.702 1.384

Freeway at 30.5 mph 20 0.038 0.031 49 0.253 0.272 24 2.523 2.124

Freeway at 18.6 mph 20 0.044 0.036 49 0.305 0.318 24 3.672 3.745

Freeway at 13.1 mph 20 0.046 0.040 49 0.330 0.341 24 4.127 4.063

Freeway Ramps

(34.6 mph)

20 0.083 0.080 49 0.408 0.488 24 3.036 2.205

Arterial/Collectors

at 24.8 mph

20 0.044 0.035 49 0.262 0.278 24 3.028 3.072

Arterial/Collectors

at 19.2 mph

20 0.060 0.054 49 0.318 0.341 24 3.970 4.794

Arterial/Collectors

at 11.6 mph

20 0.063 0.045 49 0.551 0.917 24 5.155 5.630

NYCC (7.1 mph) 20 0.122 0.111 49 0.744 1.183 24 7.306 7.824

Local Roadways

(12.9 mph)

20 0.053 0.056 49 0.336 0.360 24 4.478 5.075

Non-Freeway

Areawide Urban

Travel (19.4 mph)

19 0.057 0.047 49 0.311 0.325 24 3.571 3.060

Hot Running LA4

(19.6 mph)

20 0.036 0.019 49 0.199 0.201 24 3.175 2.945

Unified Cycle

(24.6 mph)

19 0.060 0.049 48 0.282 0.287 24 3.158 3.328
DRAFT M6.SPD.002h 43 August 24, 1999

Table 11b

Average Emissions by Emission Standard and Emission Level

Carbon Monoxide (CO)

Cycle

Tier 1 Tier 0 Normal Tier 0 High

N

Mean

(g/mi)

Std.

Dev. N

Mean

(g/mi)

Std.

Dev. N

Mean

(g/mi)

Std.

Dev.

Freeway at 63.2 mph 20 1.862 1.765 58 8.157 7.945 15 66.763 52.094

Freeway at 59.7 mph 20 3.045 1.446 58 7.755 6.410 15 65.632 54.628

Freeway at 52.9 mph 20 1.381 1.179 58 6.449 5.403 15 54.448 41.822

Freeway at 30.5 mph 20 1.305 1.636 58 5.218 3.998 15 66.377 43.185

Freeway at 18.6 mph 20 1.513 1.570 58 5.978 4.997 15 74.390 63.484

Freeway at 13.1 mph 20 1.264 1.564 58 5.596 4.464 15 82.087 77.005

Freeway Ramps

(34.6 mph)

20 2.803 2.651 58 11.665 11.170 15 84.016 57.322

Arterial/Collectors

at 24.8 mph

20 1.271 1.215 58 4.934 3.921 15 75.235 59.118

Arterial/Collectors

at 19.2 mph

20 1.562 1.638 58 6.052 5.103 15 80.793 62.646

Arterial/Collectors

at 11.6 mph

20 1.538 1.699 58 6.902 5.727 15 116.569 94.897

NYCC (7.1 mph) 20 2.652 3.068 58 9.061 8.384 15 158.041 136.341

Local Roadways

(12.9 mph)

20 1.249 1.727 58 4.924 4.212 15 92.412 87.806

Non-Freeway

Areawide Urban

Travel (19.4 mph)

19 1.357 1.580 58 5.497 4.696 15 86.628 62.322

Hot Running LA4

(19.6 mph)

20 0.892 0.846 58 3.569 2.997 15 82.194 64.114

Unified Cycle

(24.6 mph)

19 1.892 2.104 57 6.855 5.394 15 77.941 58.194
DRAFT M6.SPD.002h 44 August 24, 1999

Table 11c

Average Emissions by Emission Standard and Emission Level

Oxides of Nitrogen (NOx)

Cycle

Tier 1 Tier 0 Normal Tier 0 High

N Mean

(g/mi)

Std.

Dev.

N Mean

(g/mi)

Std.

Dev.

N Mean

(g/mi)

Std.

Dev.

Freeway at 63.2 mph 20 0.331 0.353 60 0.840 0.736 13 3.354 1.069

Freeway at 59.7 mph 20 0.340 0.287 60 0.806 0.674 13 3.270 1.021

Freeway at 52.9 mph 20 0.241 0.164 60 0.789 0.619 13 3.200 0.970

Freeway at 30.5 mph 20 0.234 0.158 60 0.709 0.558 13 3.155 0.996

Freeway at 18.6 mph 20 0.231 0.168 60 0.817 0.591 13 3.727 1.339

Freeway at 13.1 mph 20 0.187 0.143 60 0.585 0.386 13 2.805 0.995

Freeway Ramps

(34.6 mph)

20 0.324 0.222 60 1.106 0.823 13 3.998 1.435

Arterial/Collectors

at 24.8 mph

20 0.233 0.163 60 0.769 0.559 13 3.473 1.068

Arterial/Collectors

at 19.2 mph

20 0.376 0.476 60 0.905 0.660 13 3.774 1.461

Arterial/Collectors

at 11.6 mph

20 0.416 0.605 60 1.093 0.777 13 4.435 1.841

NYCC (7.1 mph) 20 0.353 0.292 60 1.093 0.672 13 4.072 1.455

Local Roadways

(12.9 mph)

20 0.311 0.426 60 0.830 0.637 13 3.735 1.463

Non-Freeway

Areawide Urban

Travel (19.4 mph)

19 0.253 0.159 60 0.796 0.583 13 3.561 1.179

Hot Running LA4

(19.6 mph)

20 0.191 0.123 60 0.591 0.457 13 3.245 1.045

Unified Cycle

(24.6 mph)

19 0.357 0.255 59 0.943 0.678 13 3.830 1.230
DRAFT M6.SPD.002h 45 August 24, 1999

Table 11d

Average Emissions by Emission Standard and Emission Level

Non-Methane Hydrocarbons (NMHC)

Cycle

Tier 1 Tier 0 Normal Tier 0 High

N Mean

(g/mi)

Std.

Dev.

N Mean

(g/mi)

Std.

Dev.

N Mean

(g/mi)

Std.

Dev.

Freeway at 63.2 mph 19 0.038 0.023 49 0.148 0.177 24 1.633 1.524

Freeway at 59.7 mph 20 0.052 0.035 49 0.154 0.162 24 1.601 1.518

Freeway at 52.9 mph 19 0.026 0.015 48 0.140 0.159 24 1.537 1.231

Freeway at 30.5 mph 19 0.025 0.020 49 0.207 0.246 24 2.290 1.847

Freeway at 18.6 mph 16 0.031 0.031 48 0.250 0.288 24 3.347 3.295

Freeway at 13.1 mph 17 0.027 0.022 49 0.259 0.310 24 3.740 3.463

Freeway Ramps

(34.6 mph)

18 0.068 0.069 47 0.357 0.444 24 2.767 1.957

Arterial/Collectors

at 24.8 mph

20 0.029 0.028 49 0.214 0.252 24 2.737 2.672

Arterial/Collectors

at 19.2 mph

18 0.042 0.041 48 0.264 0.304 24 3.616 4.291

Arterial/Collectors

at 11.6 mph

20 0.034 0.022 49 0.458 0.805 24 4.665 4.888

NYCC (7.1 mph) 19 0.082 0.089 49 0.622 1.024 24 6.571 6.609

Local Roadways

(12.9 mph)

17 0.038 0.045 48 0.280 0.334 24 4.059 4.426

Non-Freeway

Areawide Urban

Travel (19.4 mph)

18 0.038 0.033 49 0.257 0.301 24 3.245 2.635

Hot Running LA4

(19.6 mph)

20 0.020 0.009 49 0.157 0.176 24 2.945 2.770

Unified Cycle

(24.6 mph)

19 0.041 0.039 48 0.232 0.265 24 2.860 2.930
DRAFT M6.SPD.002h 46 August 24, 1999

Table 12a

Regressions of Emissions Versus Average Speed

Total Hydrocarbons (THC)

Emissions = Constant + a*(Average Speed)

Roadway Type Emission Level Speed Data

Range (mph)

Constant

(p value)

a

(p value)

Units

Freeway 1

(Tier 1)

7.1 - 13.1 1.034* -0.032* grams

per hour

Freeway 1

(Tier 1)

13.1 - 30.5 0.202

(.4780)

0.032

(.0175)

grams

per hour

Freeway 1

(Tier 1)

30.5 - 63.2 0.019

(.2157)

0.001

(.0533)

grams

per mile

Freeway 2

(Tier 0 Normal)

7.1 - 13.1 6.672* -0.170* grams

per hour

Freeway 2

(Tier 0 Normal)

13.1 - 30.5 1.933

(.2284)

0.192

(.0094)

grams

per hour

Freeway 2

(Tier 0 Normal)

30.5 - 63.2 0.315

(.0000)

-0.00226

(.0570)

grams

per mile

Freeway 3

(Tier 0 High)

7.1 - 13.1 44.558**

(.0013)

1.202**

(.0908)

grams

per hour

Freeway 3

(Tier 0 High)

13.1 - 30.5 44.558**

(.0013)

1.202**

(.0908)

grams

per hour

Freeway 3

(Tier 0 High)

30.5 - 63.2 3.193

(.0000)

-0.024

(.0836)

grams

per mile

Arterial/

Collector

1

(Tier 1)

7.1 - 24.8 0.690

(.0009)

0.017

(.0958)

grams

per hour

Arterial/

Collector

2

(Tier 0 Normal)

7.1 - 24.8 4.891

(.0001)

0.081

(.1930)

grams

per hour

Arterial/

Collector

3

(Tier 0 High)

7.1 - 24.8 44.558**

(.0013)

1.202**

(.0908)

grams

per hour

 * The values are calculated based on the NYCC at 7.1 mph and Freeway at 13.1 mph cycles.

** Freeway and Arterial/Collector cycles were combined.
DRAFT M6.SPD.002h 47 August 24, 1999

Table 12b

Regressions of Emissions Versus Average Speed

Carbon Monoxide (CO)

Emissions = Constant + a*(Average Speed)

Roadway Type Emission Level Speed Data

Range (mph)

Constant

(p value)

a

(p value)

Units

Freeway 1

(Tier 1)

7.1 - 13.1 14.730* 0.280* grams

per hour

Freeway 1

(Tier 1)

13.1 - 30.5 1.655

(.9045)

1.278

(.0454)

grams

per hour

Freeway 1

(Tier 1)

30.5 - 63.2 0.246

(.7436)

0.032

(.0263)

grams

per mile

Freeway 2

(Tier 0 Normal)

7.1 - 13.1 46.679* 2.390* grams

per hour

Freeway 2

(Tier 0 Normal)

13.1 - 30.5 15.273

(.4824)

4.788

(.0000)

grams

per hour

Freeway 2

(Tier 0 Normal)

30.5 - 63.2 2.398

(.1526)

0.0872

(.0060)

grams

per mile

Freeway 3

(Tier 0 High)

7.1 - 13.1 1206.641* -9.747* grams

per hour

Freeway 3

(Tier 0 High)

13.1 - 30.5 365.822

(.4888)

54.438

(.0275)

grams

per hour

Freeway 3

(Tier 0 High)

30.5 - 63.2 64.691

(.0147)

-0.0269

(.9559)

grams

per mile

Arterial/

Collector

1

(Tier 1)

7.1 - 24.8 10.036

(.1950)

0.941

(.0138)

grams

per hour

Arterial/

Collector

2

(Tier 0 Normal)

7.1 - 24.8 36.128

(.0054)

3.877

(.0000)

grams

per hour

Arterial/

Collector

3

(Tier 0 High)

7.1 - 24.8 863.64

(.0114)

38.563

(.0202)

grams

per hour

 * The values are calculated based on the NYCC at 7.1 mph and Freeway at 13.1 mph cycles.
DRAFT M6.SPD.002h 48 August 24, 1999

Table 12c

Regressions of Emissions Versus Average Speed

Oxides of Nitrogen (NOx)

Emissions = Constant + a*(Average Speed)

Roadway Type Emission Level Speed Data

Range (mph)

Constant

(p value)

a

(p value)

Units

Freeway 1

(Tier 1)

7.1 - 13.1 4.625* -0.154* grams

per hour

Freeway 1

(Tier 1)

13.1 - 30.5 -0.855

(.5289)

0.264

(.0001)

grams

per hour

Freeway 1

(Tier 1)

30.5 - 63.2 0.126

(.2886)

0.0031

(.1667)

grams

per mile

Freeway 2

(Tier 0 Normal)

7.1 - 13.1 8.291* 0.121* grams

per hour

Freeway 2

(Tier 0 Normal)

13.1 - 30.5 -0.957

(.7262)

0.761

(.0000)

grams

per hour

Freeway 2

(Tier 0 Normal)

30.5 - 63.2 0.594

(.0008)

0.00373

(.2575)

grams

per mile

Freeway 3

(Tier 0 High)

7.1 - 13.1 24.889* 1.364* grams

per hour

Freeway 3

(Tier 0 High)

13.1 - 30.5 0.423

(.9717)

3.232

(.0000)

grams

per hour

Freeway 3

(Tier 0 High)

30.5 - 63.2 2.980

(.0000)

0.00512

(.6389)

grams

per mile

Arterial/

Collector

1

(Tier 1)

7.1 - 24.8 2.325

(.1066)

0.170

(.0167)

grams

per hour

Arterial/

Collector

2

(Tier 0 Normal)

7.1 - 24.8 5.123

(.0027)

0.567

(.0000)

grams

per hour

Arterial/

Collector

3

(Tier 0 High)

7.1 - 24.8 14.609

(.0471)

2.812

(.0000)

grams

per hour

 * The values are calculated based on the NYCC at 7.1 mph and Freeway at 13.1 mph cycles.
DRAFT M6.SPD.002h 49 August 24, 1999

Table 12d

Regressions of Emissions Versus Average Speed

Non-Methane Hydrocarbons (NMHC)

Emissions = Constant + a*(Average Speed)

Roadway Type Emission Level Speed Data

Range (mph)

Constant

(p value)

a

(p value)

Units

Freeway 1

(Tier 1)

7.1 - 13.1 0.685* -0.028* grams

per hour

Freeway 1

(Tier 1)

13.1 - 30.5 0.00266

(.9892)

0.0236

(.0105)

grams

per hour

Freeway 1

(Tier 1)

30.5 - 63.2 0.00475

(.6971)

0.000592

(.0115)

grams

per mile

Freeway 2

(Tier 0 Normal)

7.1 - 13.1 5.796* -0.176* grams

per hour

Freeway 2

(Tier 0 Normal)

13.1 - 30.5 1.328

(.3602)

0.165

(.0131)

grams

per hour

Freeway 2

(Tier 0 Normal)

30.5 - 63.2 0.259

(.0000)

-0.00189

(.0773)

grams

per mile

Freeway 3

(Tier 0 High)

7.1 - 13.1 40.178* 1.103* grams

per hour

Freeway 3

(Tier 0 High)

13.1 - 30.5 37.404

(.0580)

1.107

(.2142)

grams

per hour

Freeway 3

(Tier 0 High)

30.5 - 63.2 2.899

(.0000)

-0.022

(.0773)

grams

per mile

Arterial/

Collector

1

(Tier 1)

7.1 - 24.8 0.399

(.0082)

0.0118

(.1048)

grams

per hour

Arterial/

Collector

2

(Tier 0 Normal)

7.1 - 24.8 4.111

(.0003)

0.0617

(.2612)

grams

per hour

Arterial/

Collector

3

(Tier 0 High)

7.1 - 24.8 42.589

(.0023)

1.017

(.1299)

grams

per hour

 * The values are calculated based on the NYCC at 7.1 mph and Freeway at 13.1 mph cycles.
DRAFT M6.SPD.002h 50 August 24, 1999

Table 13

Freeway Ramp and Local Roadway Emissions

As a Function of Hot Running LA4 Emissions

In Grams/Hour

Emissions (g/hr) = Constant + a*(LA4) + b*(LA42

)

where LA4 is the hot running LA4 emissions in g/hr

Roadway Type Pollutant Constant

(p value)

a

(p value)

b

(p value)

R2

Freeway Ramp

(34.6 mph)

THC 4.560

(.0302)

2.046

(.0000)

-0.00356

(.0000)

0.934

Freeway Ramp

(34.6 mph)

CO 224.333

(.0010)

2.040

(.0000)

-0.000145

(.0074)

0.848

Freeway Ramp

(34.6 mph)

NOx 5.353

(.1103)

2.863

(.0000)

-.0101

(.0019)

0.866

Freeway Ramp

(34.6 mph)

NMHC 4.368

(.0193)

2.014

(.0000)

-0.00387

(.0000)

0.934

Local Roadways

(12.9 mph)

THC -0.479

(.8627)

1.045

(.0000)

-0.000724

(.3090)

0.765

Local Roadways

(12.9 mph)

CO 13.795

(.7042)

0.721

(.0000)

0.000

(.9600)

0.803

Local Roadways

(12.9 mph)

NOx 1.870

(.0424)

0.701

(.0000)

0.000609

(.4803)

0.919

Local Roadways

(12.9 mph)

NMHC -0.896

(.7115)

1.135

(.0000)

-0.00161

(.0201)

0.764
DRAFT M6.SPD.002h 51 August 24, 1999

Table 14

Emission Offset

(Predicted Freeway Emissions - Average Hot Running LA4 Emissions)

Level 1 (Tier 1)

(grams per mile)

Level 2 (Tier 0)

(grams per mile)

Level 3 (High Emitters)

(grams per mile)

Fwy LA4 Offset Fwy LA4 Offset Fwy LA4 Offset

THC 0.042 0.036 0.006 0.290 0.199 0.091 3.476 3.175 0.301

CO 1.363 0.892 0.471 5.567 3.569 1.998 73.102 82.194 -9.092

NOx 0.220 0.191 0.029 0.712 0.591 0.121 3.253 3.245 0.008

NMHC 0.024 0.020 0.004 0.233 0.157 0.076 3.153 2.945 0.208
DRAFT M6.SPD.002h 52 August 24, 1999

Table 15

Arterial/Collector Emission Offsets

(Predicted Arterial/Collector Emissions - Predicted Freeway Emissions)

Pollutant

Average Speed*

(miles per hour)

Level 1

(grams per mile)

Level 2

(grams per mile)

Level 3

(grams per mile)

THC 10 0.014 0.073 0

15 0.018 0.086 0

20 0.009 0.037 0

25 0.005 0.007 0

30 0.001 0 0

CO 10 0.192 0.431 14.010

15 0.222 0.479 17.313

20 0.082 0.131 9.016

25 0 0 4.038

30 0 0 0.719

NOx 10 0.094 0.171 0.420

15 0.118 0.211 0.526

20 0.065 0.110 0.290

25 0.033 0.049 0.148

30 0.012 0.009 0.053

NMHC 10 0.012 0.069 0

15 0.015 0.082 0

20 0.008 0.035 0

25 0.004 0.008 0

30 0.001 0 0

* Arterial/Collector Emission Offsets below 10 mph and over 30 mph are zero.
DRAFT M6.SPD.002h 53 August 24, 1999

Table 16

Speed Correction Factors

For Freeways

By Emission Level*

Avg.

Speed

(mph)

Total Hydrocarbons

(THC)

Carbon Monoxide

(CO)

Oxides of Nitrogen

(NOx)

Non-Methane HC

(NMHC)

Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Level 1 Level 2 Level 3

7.1 2.71 2.65 2.15 1.73 1.61 2.19 2.26 1.81 1.50 2.87 2.75 2.14

10 1.71 1.71 1.63 1.29 1.27 1.52 1.40 1.28 1.18 1.69 1.73 1.62

15 1.08 1.10 1.20 1.02 1.04 1.08 0.94 0.98 1.00 1.00 1.09 1.20

19.6 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00

20 1.00 0.99 0.99 1.00 1.00 0.99 1.00 1.00 1.00 1.00 0.99 0.99

25 0.95 0.93 0.86 0.99 0.97 0.94 1.04 1.01 1.00 1.00 0.94 0.86

30 0.91 0.88 0.77 0.98 0.95 0.91 1.07 1.02 1.00 1.00 0.90 0.77

35 0.91 0.81 0.68 1.00 0.98 0.87 1.07 1.02 1.00 1.07 0.83 0.68

40 0.97 0.77 0.64 1.12 1.06 0.87 1.14 1.04 1.00 1.20 0.79 0.64

45 1.04 0.73 0.61 1.24 1.14 0.87 1.21 1.07 1.00 1.32 0.74 0.61

50 1.10 0.69 0.57 1.36 1.21 0.87 1.28 1.09 1.00 1.45 0.70 0.57

55 1.17 0.65 0.54 1.47 1.29 0.86 1.35 1.12 1.00 1.57 0.66 0.54

60 1.24 0.61 0.50 1.59 1.37 0.86 1.42 1.15 1.01 1.70 0.62 0.50

65 1.30 0.57 0.47 1.71 1.45 0.86 1.49 1.17 1.02 1.82 0.58 0.47

* Emission levels shown as Fwy emissions in Table 14. See Section 4.6.
DRAFT M6.SPD.002h 54 August 24, 1999

Table 17

Speed Correction Factors

For Arterial/Collector Roadways

By Emission Level*

Avg.

Speed

(mph)

Total Hydrocarbons

(THC)

Carbon Monoxide

(CO)

Oxides of Nitrogen

(NOx)

Non-Methane HC

(NMHC)

Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Level 1 Level 2 Level 3

7.1 2.71 2.65 2.15 1.73 1.61 2.19 2.26 1.81 1.50 2.87 2.75 2.14

10 2.04 1.96 1.63 1.43 1.35 1.71 1.82 1.52 1.31 2.18 2.03 1.62

15 1.49 1.40 1.20 1.18 1.13 1.32 1.47 1.28 1.16 1.62 1.44 1.20

20 1.22 1.12 0.99 1.06 1.02 1.12 1.30 1.16 1.09 1.34 1.15 0.99

25 1.05 0.95 0.86 0.99 0.97 1.00 1.19 1.08 1.04 1.17 0.97 0.86

30 0.95 0.88 0.77 0.98 0.95 0.92 1.12 1.04 1.01 1.06 0.90 0.77

35 0.91 0.81 0.68 1.00 0.98 0.87 1.07 1.02 1.00 1.07 0.83 0.68

40 0.97 0.77 0.64 1.12 1.06 0.87 1.14 1.04 1.00 1.20 0.79 0.64

45 1.04 0.73 0.61 1.24 1.14 0.87 1.21 1.07 1.00 1.32 0.74 0.61

50 1.10 0.69 0.57 1.36 1.21 0.87 1.28 1.09 1.00 1.45 0.70 0.57

55 1.17 0.65 0.54 1.47 1.29 0.86 1.35 1.12 1.00 1.57 0.66 0.54

60 1.24 0.61 0.50 1.59 1.37 0.86 1.42 1.15 1.01 1.70 0.62 0.50

65 1.30 0.57 0.47 1.71 1.45 0.86 1.49 1.17 1.02 1.82 0.58 0.47

* Emission levels shown as Fwy emissions in Table 14. See Section 4.6.
DRAFT M6.SPD.002h 55 August 24, 1999

Figures
DRAFT M6.SPD.002h 56 August 24, 1999

Figure 1a.

Facility Cycles Ratio of Means, HC by 

Emitter Level Groups

0.000

0.500

1.000

1.500

2.000

2.500

3.000

3.500

4.000

0 20 40 60 80

Average Speed (mph)

Ratio of Means 

(HC/Running LA4)

Low Emitters

High Emitters

Figure 1b.

Facility Cycles Ratio of Means, CO by 

Emitter Level Groups

0.000

0.500

1.000

1.500

2.000

2.500

3.000

3.500

0 20 40 60 80

Average Speed (mph)

Ratio of Means 

(CO/Running LA4)

Low Emitters

High Emitters
DRAFT M6.SPD.002h 57 August 24, 1999

F ig u re 1c.

Facility Cycles Ratio of M eans, NOx 

by Emitter Level Groups

0.000

0.200

0.400

0.600

0.800

1.000

1.200

1.400

1.600

1.800

2.000

0 2 0 4 0 6 0 8 0

Average Speed (m ph)

Ratio of Means 

(NOx/Running LA4)

L ow E m itters

H ig h E m itters
DRAFT M6.SPD.002h 58 August 24, 1999

Figure 2a.

Facility Cycle Data, HC

0.000

0.500

1.000

1.500

2.000

2.500

3.000

3.500

4.000

0 20 40 60 80

Average Speed

Ratio of M eans 

(HC/Running LA4)

Legend for Figures 2a, b and c

Arte ria l/Colle ctors

Freew ays

LA92

Are a -w ide , non-fre e w a y

Local

Ramp
DRAFT M6.SPD.002h 59 August 24, 1999

F ig u re 2b .

Facility Cycle Data, CO

0.000

0.500

1.000

1.500

2.000

2.500

3.000

3.500

0 20 40 60 80

Average Speed

Ratio of M ean s 

(C O /Ru n nin g L A4

F ig u re 2c.

Facility Cycle Data, NOx

0.000

0.200

0.400

0.600

0.800

1.000

1.200

1.400

1.600

1.800

2.000

0 20 40 60 80

Average Speed

Ra tio o f M ean s 

(NO x/Ru n ning L A

4
DRAFT M6.SPD.002h 60 August 24, 1999

Figure 3a.

Facility Cycle Data, THC

Tier 0 vs. Tier 1

0.000

0.500

1.000

1.500

2.000

2.500

3.000

3.500

4.000

0 20 40 60 80

Average Speed

Ratio of Means 

(THC/Running LA4)

Legend for Figures 3a, 3b and 3c

0.000

2.000

4.000

0 100

Arterial/Collectors, Tier 0

Freeways, Tier 0

Local, Tier 0

Ramp, Tier 0

LA92, Tier 0

Area-wide, non-freeway, Tier 0

Arterial/Collectors, Tier 1

Freeways, Tier 1

Local, Tier 1

Ramp, Tier 1

LA92, Tier 1

Area-wide, non-freeway, Tier 1
DRAFT M6.SPD.002h 61 August 24, 1999

Figure 3b.

Facility Cycle Data, CO

Tier 0 vs. Tier 1

0.000

1.000

2.000

3.000

4.000

5.000

6.000

0 20 40 60 80

Average Speed

Ratio of Means 

(CO/Running 

LA4)

Figure 3c.

Facility Cycle Data, NOx

Tier 0 vs. Tier 1

0.000

0.500

1.000

1.500

2.000

2.500

0 20 40 60 80

Average Speed

Ratio of Means 

(NOx/Running LA4)
DRAFT M6.SPD.002h 62 August 24, 1999

Figure 4b

Carbon Monoxide (CO)

Freeway Emission Levels

0

20

40

60

80

100

120

140

160

180

5 10 15 20 25 30 35 40

Average Speed (mph)

Emissions in Grams Per Mile

Level 1 (Tier 1 Normal)

Level 2 (Tier 0 Normal)

Level 3 (Tier 0 High)

Figure 4a

Total Hydrocarbon (THC)

Freeway Emission Levels

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

5 10 15 20 25 30 35 40

Average Speed (mph)

Emissions in Grams Per Mile

Level 1 (Tier 1 Norm al)

Level 2 (Tier 0 Norm al)

Level 3 (Tier 0 High)
DRAFT M6.SPD.002h 63 August 24, 1999

Figure 4d

Non-Methane Hydrocarbons (NMHC)

Freeway Emission Levels

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

5 10 15 20 25 30 35 40

Average Speed (mph)

Emissions in Grams Per Mile

Level 1 (Tier 1 Normal)

Level 2 (Tier 0 Normal)

Level 3 (Tier 0 High)

Figure 4c

Oxides of Nitrogen (NOx)

Freeway Emission Levels

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5 10 15 20 25 30 35 40

Average Speed (mph)

Emissions in Grams Per Mile

Level 1 (Tier 1 Normal)

Level 2 (Tier 0 Normal)

Level 3 (Tier 0 High)
DRAFT M6.SPD.002h 64 August 24, 1999

Figure 5a

Freeway Speed Correction Factors for 

Total Hydrocarbons (THC)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 10 20 30 40 50 60 70

Average Speed (mph)

Speed Correction Factor

Emission Level 1

(0.04 g/mi)

Emission Level 2

(0.29 g/mi)

Emission Level 3

(3.48 g/mi)

Figure 5b

Freeway Speed Correction Factors for 

Carbon Monoxide (CO)

0.0

0.5

1.0

1.5

2.0

2.5

0 10 20 30 40 50 60 70

Average Speed (mph)

Speed Correction Factor

Emission Level 1

(1.4 g/mi)

Emission Level 2

(5.6 g/mi)

Emission Level 3

(73.1 g/mi)
DRAFT M6.SPD.002h 65 August 24, 1999

Figure 5d

Freeway Speed Correction Factors for 

Non-Methane Hydrocarbons (NMHC)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0 10 20 30 40 50 60 70

Average Speed (mph)

Speed Correction Factor

Emission Level 1

(0.02 g/mi)

Emission Level 2

(0.23 g/mi)

Emission Level 3

(3.15 g/mi)

Figure 5c

Freeway Speed Correction Factors for 

Oxides of Nitrogen (NOx)

0.0

0.5

1.0

1.5

2.0

2.5

0 10 20 30 40 50 60 70

Average Speed (mph)

Speed Correction Factor

Emission Level 1

(0.22 g/mi)

Emission Level 2

(0.71 g/mi)

Emission Level 3

(3.25 g/mi)
DRAFT M6.SPD.002h 66 August 24, 1999

Figure 6a

Comparison to MOBILE5

Speed Correction Factors for 

Total Hydrocarbons (THC)

0.00

0.50

1.00

1.50

2.00

2.50

3.00

0 10 20 30 40 50 60 70

Average Speed (mph)

Speed Correction Factor

Emission Level 1 (0.04 g/mi)

Emission Level 2 (0.29 g/mi)

Emission Level 3 (3.48 g/mi)

M5 1975 MYR

M5 1981 MYR

M5 1991+ MYR

Figure 6b

Comparison to MOBILE5

Speed Correction Factors for 

Carbon Monoxide (CO)

0.00

0.50

1.00

1.50

2.00

2.50

0 10 20 30 40 50 60 70

Average Speed (mph)

Speed Correction Factor

Emission Level 1 (1.4 g/mi)

Emission Level 2 (5.6 g/mi)

Emission Level 3 (73.1 g/mi)

M5 1975 MYR

M5 1981 MYR

M5 1993+ MYR
DRAFT M6.SPD.002h 67 August 24, 1999

Figure 7a

Arterial/Collector Speed Correction Factors

Total Hydrocarbons (THC)

Level 1 Emissions (0.04 g/mi)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

5 10 15 20 25 30 35 40

Average Speed (mph)

Speed Correction Factor

M5 1975 MYR

M5 1981 MYR

M5 1993+ MYR

Freeway Level 1

Arterial/Collector Level 1

Figure 6c

Comparison to MOBILE5

Speed Correction Factors for 

Oxides of Nitrogen (NOx)

0.00

0.50

1.00

1.50

2.00

2.50

0 10 20 30 40 50 60 70

Average Speed (mph)

Speed Correction Factor

Emission Level 1 (0.22 g/mi)

Emission Level 2 (0.71 g/mi)

Emission Level 3 (3.25 g/mi)

M5 1975 MYR

M5 1981 MYR

M5 1993+ MYR
DRAFT M6.SPD.002h 68 August 24, 1999

Figure 7b

Arterial/Collector Speed Correction Factors

Total Hydrocarbons (THC)

Level 2 Emissions (0.29 g/mi)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

5 10 15 20 25 30 35 40

Average Speed (mph)

Speed Correction Factor

M5 1975 MYR

M5 1981 MYR

M5 1993+ MYR

Freeway Level 1

Arterial/Collector Level 1

Figure 7c

Arterial/Collector Speed Correction Factors

Total Hydrocarbons (THC)

Level 3 Emissions (3.48 g/mi)

0.0

0.5

1.0

1.5

2.0

2.5

5 10 15 20 25 30 35 40

Average Speed (mph)

Speed Correction Factor

M5 1975 MYR

M5 1981 MYR

M5 1993+ MYR

Freeway Level 3

Arterial/Collector Level 3
DRAFT M6.SPD.002h 69 August 24, 1999

Figure 7d

Arterial/Collector Speed Correction Factors

Carbon Monoxide (CO)

Level 1 Emissions (1.36 g/mi)

0.0

0.5

1.0

1.5

2.0

2.5

5 10 15 20 25 30 35 40

Average Speed (mph)

Speed Correction Factor

M5 1975 MYR

M5 1981 MYR

M5 1993+ MYR

Freeway Level 1

Arterial/Collector Level 1

Figure 7e

Arterial/Collector Speed Correction Factors

Carbon Monoxide (CO)

Level 2 Emissions (5.57 g/mi)

0.0

0.5

1.0

1.5

2.0

2.5

5 10 15 20 25 30 35 40

Average Speed (mph)

Speed Correction Factor

M5 1975 MYR

M5 1981 MYR

M5 1993+ MYR

Freeway Level 2

Arterial/Collector Level 2
DRAFT M6.SPD.002h 70 August 24, 1999

Figure 7f

Arterial/Collector Speed Correction Factors

Carbon Monoxide (CO)

Level 3 Emissions (73.1 g/mi)

0.0

0.5

1.0

1.5

2.0

2.5

5 10 15 20 25 30 35 40

Average Speed (mph)

Speed Correction Factor

M5 1975 MYR

M5 1981 MYR

M5 1993+ MYR

Freeway Level 3

Arterial/Collector Level 3

Figure 7g

Arterial/Collector Speed Correction Factors

Oxides of Nitrogen (NOx)

Level 1 Emissions (0.22 g/mi)

0.0

0.5

1.0

1.5

2.0

2.5

5 10 15 20 25 30 35 40

Average Speed (mph)

Speed Correction Factor

M5 1975 MYR

M5 1981 MYR

M5 1993+ MYR

Freeway Level 1

Arterial/Collector Level 1
DRAFT M6.SPD.002h 71 August 24, 1999

Figure 7h

Arterial/Collector Speed Correction Factors

Oxides of Nitrogen (NOx)

Level 2 Emissions (0.71 g/mi)

0.0

0.5

1.0

1.5

2.0

2.5

5 10 15 20 25 30 35 40

Average Speed (mph)

Speed Correction Factor

M5 1975 MYR

M5 1981 MYR

M5 1993+ MYR

Freeway Level 2

Arterial/Collector Level 2

Figure 7i

Arterial/Collector Speed Correction Factors

Oxides of Nitrogen (NOx)

Level 3 Emissions (3.25 g/mi)

0.0

0.5

1.0

1.5

2.0

2.5

5 10 15 20 25 30 35 40

Average Speed (mph)

Speed Correction Factor

M5 1975 MYR

M5 1981 MYR

M5 1993+ MYR

Freeway Level 3

Arterial/Collector Level 3
DRAFT M6.SPD.002h 72 August 24, 1999

Appendices
DRAFT M6.SPD.002h 73 August 24, 1999

Appendix A

MAIN EFFECTS & INTERACTIONS WITH SPEED

All Vehicles

--------------------------------------------------------------

| | THC | NMHC | CO | NOX |

|----------------------------+-------+-------+-------+-------|

|FACTOR | | | | |

|----------------------------| | | | |

|S | 0.0000| 0.0001| 0.0000| 0.0000|

|----------------------------+-------+-------+-------+-------|

|EMIT_CLASS | 0.0000| 0.0000| 0.0000| 0.0000|

|----------------------------+-------+-------+-------+-------|

|S*EMIT_CLASS | 0.1411| 0.1271| 0.0152| 0.9894|

--------------------------------------------------------------
DRAFT M6.SPD.002h 74 August 24, 1999

EMIT NORMAL - ACTUAL TIER CLASS

--------------------------------------------------------------

| | THC | NMHC | CO | NOX |

|----------------------------+-------+-------+-------+-------|

|ROAD |FACTOR | | | | |

|-------------+--------------| | | | |

|ART/FWY |ROADTYPE | 0.0046| 0.0050| 0.0006| 0.0000|

| |--------------+-------+-------+-------+-------|

| |S*ROADTYPE | 0.0354| 0.0440| 0.0020| 0.0000|

| |--------------+-------+-------+-------+-------|

| |VEH_TYPE | 0.0016| 0.0404| 0.0031| 0.0012|

| |--------------+-------+-------+-------+-------|

| |S*VEH_TYPE | 0.1754| 0.1802| 0.8680| 0.5723|

| |--------------+-------+-------+-------+-------|

| |STANDARD | 0.0000| 0.0000| 0.0000| 0.0000|

| |--------------+-------+-------+-------+-------|

| |S*STANDARD | 0.0002| 0.0001| 0.0576| 0.6491|

--------------------------------------------------------------

|LOCAL |VEH_TYPE | 0.0830| 0.5008| 0.4038| 0.0124|

| |--------------+-------+-------+-------+-------|

| |STANDARD | 0.0000| 0.0000| 0.0000| 0.0028|

|-------------+--------------+-------+-------+-------+-------|

|RAMP |VEH_TYPE | 0.2922| 0.7707| 0.0443| 0.0018|

| |--------------+-------+-------+-------+-------|

| |STANDARD | 0.0003| 0.0007| 0.0002| 0.0000|

--------------------------------------------------------------

EMIT HIGH - ACTUAL TIER CLASS

--------------------------------------------------------------

| | THC | NMHC | CO | NOX |

|----------------------------+-------+-------+-------+-------|

|ROAD |FACTOR | | | | |

|-------------+--------------| | | | |

|ART/FWY |ROADTYPE | 0.1236| 0.1307| 0.3307| 0.0000|

| |--------------+-------+-------+-------+-------|

| |S*ROADTYPE | 0.1176| 0.1203| 0.6233| 0.0000|

| |--------------+-------+-------+-------+-------|

| |VEH_TYPE | 0.5942| 0.5693| 0.8984| 0.3961|

| |--------------+-------+-------+-------+-------|

| |S*VEH_TYPE | 0.0641| 0.0699| 0.0241| 0.9560|

| |--------------+-------+-------+-------+-------|

| |STANDARD | N/A| N/A| N/A| N/A|

| |--------------+-------+-------+-------+-------|

| |S*STANDARD | N/A| N/A| N/A| N/A|

--------------------------------------------------------------

|LOCAL |VEH_TYPE | 0.8787| 0.8821| 0.5511| 0.6093|

| |--------------+-------+-------+-------+-------|

| |STANDARD | N/A| N/A| N/A| N/A|

|-------------+--------------+-------+-------+-------+-------|

|RAMP |VEH_TYPE | 0.3701| 0.4075| 0.1471| 0.6942|

| |--------------+-------+-------+-------+-------|

| |STANDARD | N/A| N/A| N/A| N/A|

--------------------------------------------------------------
DRAFT M6.SPD.002h 75 August 24, 1999

EMIT NORMAL - CLEAN TIER 0 CLASS

--------------------------------------------------------------

| | THC | NMHC | CO | NOX |

|----------------------------+-------+-------+-------+-------|

|ROAD |FACTOR | | | | |

|-------------+--------------| | | | |

|ART/FWY |ROADTYPE | 0.0046| 0.0050| 0.0006| 0.0000|

| |--------------+-------+-------+-------+-------|

| |S*ROADTYPE | 0.0354| 0.0440| 0.0020| 0.0000|

| |--------------+-------+-------+-------+-------|

| |VEH_TYPE | 0.0004| 0.0243| 0.0062| 0.0026|

| |--------------+-------+-------+-------+-------|

| |S*VEH_TYPE | 0.1322| 0.1476| 0.8361| 0.5608|

| |--------------+-------+-------+-------+-------|

| |CLEANT0 | 0.0000| 0.0000| 0.0000| 0.0000|

| |--------------+-------+-------+-------+-------|

| |S*CLEANT0 | 0.0002| 0.0001| 0.0576| 0.6491|

--------------------------------------------------------------

|LOCAL |VEH_TYPE | 0.0572| 0.4049| 0.1660| 0.0184|

| |--------------+-------+-------+-------+-------|

| |CLEANT0 | 0.0000| 0.0000| 0.0000| 0.0028|

|-------------+--------------+-------+-------+-------+-------|

|RAMP |VEH_TYPE | 0.1570| 0.5501| 0.0201| 0.0009|

| |--------------+-------+-------+-------+-------|

| |CLEANT0 | 0.0003| 0.0007| 0.0002| 0.0000|

--------------------------------------------------------------

EMIT HIGH - CLEAN TIER 0 CLASS

--------------------------------------------------------------

| | THC | NMHC | CO | NOX |

|----------------------------+-------+-------+-------+-------|

|ROAD |FACTOR | | | | |

|-------------+--------------| | | | |

|ART/FWY |ROADTYPE | 0.1236| 0.1307| 0.3307| 0.0000|

| |--------------+-------+-------+-------+-------|

| |S*ROADTYPE | 0.1176| 0.1203| 0.6233| 0.0000|

| |--------------+-------+-------+-------+-------|

| |VEH_TYPE | 0.5942| 0.5693| 0.8984| 0.3961|

| |--------------+-------+-------+-------+-------|

| |S*VEH_TYPE | 0.0641| 0.0699| 0.0241| 0.9560|

| |--------------+-------+-------+-------+-------|

| |CLEANT0 | .| .| .| .|

| |--------------+-------+-------+-------+-------|

| |S*CLEANT0 | .| .| .| .|

--------------------------------------------------------------

|LOCAL |VEH_TYPE | 0.8787| 0.8821| 0.5511| 0.6093|

| |--------------+-------+-------+-------+-------|

| |CLEANT0 | .| .| .| .|

|-------------+--------------+-------+-------+-------+-------|

|RAMP |VEH_TYPE | 0.3701| 0.4075| 0.1471| 0.6942|

| |--------------+-------+-------+-------+-------|

| |CLEANT0 | .| .| .| .|

--------------------------------------------------------------
DRAFT M6.SPD.002h 76 August 24, 1999

EMIT NORMAL

--------------------------------------------------------------

| | P |

| |-------------------------------|

| | THC | NMHC | CO | NOX |

| |-------+-------+-------+-------|

| | PROB | PROB | PROB | PROB |

|----------------------------+-------+-------+-------+-------|

|ROAD |FACTOR | | | | |

|-------------+--------------| | | | |

|ART/FWY |ROADWAY TYPE | 0.0001| 0.0000| 0.0405| 0.0000|

| |--------------+-------+-------+-------+-------|

| |VEHICLE CLASS | 0.0000| 0.0640| 0.0000| 0.0000|

| |--------------+-------+-------+-------+-------|

| |STANDARD | 0.0000| 0.0000| 0.0000| 0.0000|

|-------------+--------------+-------+-------+-------+-------|

|LOCAL |VEHICLE CLASS | 0.1017| 0.5022| 0.1380| 0.0408|

| |--------------+-------+-------+-------+-------|

| |STANDARD | 0.0000| 0.0000| 0.0000| 0.0000|

|-------------+--------------+-------+-------+-------+-------|

|RAMP |VEHICLE CLASS | 0.2047| 0.6109| 0.0213| 0.0035|

| |--------------+-------+-------+-------+-------|

| |STANDARD | 0.0000| 0.0000| 0.0000| 0.0000|

--------------------------------------------------------------

EMIT HIGH

--------------------------------------------------------------

| | P |

| |-------------------------------|

| | THC | NMHC | CO | NOX |

| |-------+-------+-------+-------|

| | PROB | PROB | PROB | PROB |

|----------------------------+-------+-------+-------+-------|

|ROAD |FACTOR | | | | |

|-------------+--------------| | | | |

|ART/FWY |ROADWAY TYPE | 0.9736| 0.9570| 0.0151| 0.0201|

| |--------------+-------+-------+-------+-------|

| |VEHICLE CLASS | 0.0667| 0.0873| 0.0004| 0.1444|

| |--------------+-------+-------+-------+-------|

| |STANDARD | .| .| .| .|

--------------------------------------------------------------

Note: these probabilities are for tests of factor main effects, not

interactions with speed.
DRAFT M6.SPD.002h 77 August 24, 1999

 EMIT NORMAL - CLEAN TIER 0 CLASS --------------------------------------------------------------

| | THC | NMHC | CO | NOX |

|----------------------------+-------+-------+-------+-------|

|ROAD |FACTOR | | | | |

|-------------+--------------| | | | |

|ART/FWY |ROADTYPE | 0.0001| 0.0000| 0.0405| 0.0000|

| |--------------+-------+-------+-------+-------|

| |VEH_TYPE | 0.0000| 0.0186| 0.0000| 0.0000|

| |--------------+-------+-------+-------+-------|

| |STANDARD | 0.0000| 0.0000| 0.0000| 0.0000|

|-------------+--------------+-------+-------+-------+-------|

|LOCAL |VEH_TYPE | 0.0572| 0.4049| 0.1660| 0.0184|

| |--------------+-------+-------+-------+-------|

| |STANDARD | 0.0000| 0.0000| 0.0000| 0.0028|

|-------------+--------------+-------+-------+-------+-------|

|RAMP |VEH_TYPE | 0.1570| 0.5501| 0.0201| 0.0009|

| |--------------+-------+-------+-------+-------|

| |STANDARD | 0.0003| 0.0007| 0.0002| 0.0000|

--------------------------------------------------------------

EMIT NORMAL - ACTUAL TIER CLASS --------------------------------------------------------------

| | THC | NMHC | CO | NOX |

|----------------------------+-------+-------+-------+-------|

|ROAD |FACTOR | | | | |

|-------------+--------------| | | | |

|ART/FWY |ROADTYPE | 0.0001| 0.0000| 0.0405| 0.0000|

| |--------------+-------+-------+-------+-------|

| |VEH_TYPE | 0.0000| 0.0686| 0.0001| 0.0000|

| |--------------+-------+-------+-------+-------|

| |STANDARD | 0.0000| 0.0000| 0.0000| 0.0000|

|-------------+--------------+-------+-------+-------+-------|

|LOCAL |VEH_TYPE | 0.0830| 0.5008| 0.4038| 0.0124|

| |--------------+-------+-------+-------+-------|

| |STANDARD | 0.0002| 0.0001| 0.0000| 0.0024|

|-------------+--------------+-------+-------+-------+-------|

|RAMP |VEH_TYPE | 0.2922| 0.7707| 0.0443| 0.0018|

| |--------------+-------+-------+-------+-------|

| |STANDARD | 0.0013| 0.0002| 0.0001| 0.0010|

--------------------------------------------------------------

EMIT HIGH

--------------------------------------------------------------

| | THC | NMHC | CO | NOX |

|----------------------------+-------+-------+-------+-------|

|ROAD |FACTOR | | | | |

|-------------+--------------| | | | |

|ART/FWY |ROADTYPE | 0.9736| 0.9570| 0.0151| 0.0201|

| |--------------+-------+-------+-------+-------|

| |VEH_TYPE | 0.0667| 0.0873| 0.0004| 0.1444|

| |--------------+-------+-------+-------+-------|

| |STANDARD | .| .| .| .|

|-------------+--------------+-------+-------+-------+-------|

|LOCAL |VEH_TYPE | 0.8787| 0.8821| 0.5511| 0.6093|

| |--------------+-------+-------+-------+-------|

| |STANDARD | .| .| .| .|

|-------------+--------------+-------+-------+-------+-------|

|RAMP |VEH_TYPE | 0.3701| 0.4075| 0.1471| 0.6942|

| |--------------+-------+-------+-------+-------|

| |STANDARD | .| .| .| .|

--------------------------------------------------------------

GLM P-VALUES FOR MODELS WITH NO SPEED INTERACTIONS (FROM FACVEHA.SAS)
DRAFT M6.SPD.002h 78 August 24, 1999

EMIT NORMAL - CLEAN TIER 0 CLASS --------------------------------------------------------------

| | P |

| |-------------------------------|

| | THC | NMHC | CO | NOX |

| |-------+-------+-------+-------|

| | PROB | PROB | PROB | PROB |

|----------------------------+-------+-------+-------+-------|

|ROAD |FACTOR | | | | |

|-------------+--------------| | | | |

|ART/FWY |S*ROADTYPE | 0.0354| 0.0440| 0.0020| 0.0000|

| |--------------+-------+-------+-------+-------|

| |S*VEH_TYPE | 0.1322| 0.1476| 0.8361| 0.5608|

| |--------------+-------+-------+-------+-------|

| |S*STANDARD | 0.0002| 0.0001| 0.0576| 0.6491|

--------------------------------------------------------------

EMIT HIGH - CLEAN TIER 0 CLASS

--------------------------------------------------------------

| | P |

| |-------------------------------|

| | THC | NMHC | CO | NOX |

| |-------+-------+-------+-------|

| | PROB | PROB | PROB | PROB |

|----------------------------+-------+-------+-------+-------|

|ROAD |FACTOR | | | | |

|-------------+--------------| | | | |

|ART/FWY |S*ROADTYPE | 0.1176| 0.1203| 0.6233| 0.0000|

| |--------------+-------+-------+-------+-------|

| |S*VEH_TYPE | 0.0641| 0.0699| 0.0241| 0.9560|

| |--------------+-------+-------+-------+-------|

| |S*STANDARD | .| .| .| .|

--------------------------------------------------------------

EMIT NORMAL - CLEAN ACTUAL TIER CLASS

--------------------------------------------------------------

| | P |

| |-------------------------------|

| | THC | NMHC | CO | NOX |

| |-------+-------+-------+-------|

| | PROB | PROB | PROB | PROB |

|----------------------------+-------+-------+-------+-------|

|ROAD |FACTOR | | | | |

|-------------+--------------| | | | |

|ART/FWY |S*ROADTYPE | 0.0354| 0.0440| 0.0020| 0.0000|

| |--------------+-------+-------+-------+-------|

| |S*VEH_TYPE | 0.1754| 0.1802| 0.8680| 0.5723|

| |--------------+-------+-------+-------+-------|

| |S*STANDARD | 0.0024| 0.0020| 0.0560| 0.0151|

--------------------------------------------------------------

EMIT HIGH - CLEAN ACTUAL TIER CLASS

--------------------------------------------------------------

| | P |

| |-------------------------------|

| | THC | NMHC | CO | NOX |

| |-------+-------+-------+-------|

| | PROB | PROB | PROB | PROB |

|----------------------------+-------+-------+-------+-------|

|ROAD |FACTOR | | | | |

|-------------+--------------| | | | |

|ART/FWY |S*ROADTYPE | 0.1176| 0.1203| 0.6233| 0.0000|

| |--------------+-------+-------+-------+-------|

| |S*VEH_TYPE | 0.0641| 0.0699| 0.0241| 0.9560|

| |--------------+-------+-------+-------+-------|

| |S*STANDARD | .| .| .| .|

--------------------------------------------------------------

GLM P-VALUES FOR MODELS WITH NO SPEED INTERACTIONS (FROM FACVEHA.SAS)
DRAFT M6.SPD.002h 79 August 24, 1999

EMIT NORMAL - CLEAN TIER 0 CLASS --------------------------------------------------------------

| | P |

| |-------------------------------|

| | THC | NMHC | CO | NOX |

| |-------+-------+-------+-------|

| | PROB | PROB | PROB | PROB |

|----------------------------+-------+-------+-------+-------|

|ROAD |FACTOR | | | | |

|-------------+--------------| | | | |

|ART/FWY |ROADTYPE | 0.0046| 0.0050| 0.0006| 0.0000|

| |--------------+-------+-------+-------+-------|

| |VEH_TYPE | 0.0004| 0.0243| 0.0062| 0.0026|

| |--------------+-------+-------+-------+-------|

| |STANDARD | 0.0000| 0.0000| 0.0000| 0.0000|

--------------------------------------------------------------

EMIT HIGH - CLEAN TIER 0 CLASS

--------------------------------------------------------------

| | P |

| |-------------------------------|

| | THC | NMHC | CO | NOX |

| |-------+-------+-------+-------|

| | PROB | PROB | PROB | PROB |

|----------------------------+-------+-------+-------+-------|

|ROAD |FACTOR | | | | |

|-------------+--------------| | | | |

|ART/FWY |ROADTYPE | 0.1236| 0.1307| 0.3307| 0.0000|

| |--------------+-------+-------+-------+-------|

| |VEH_TYPE | 0.5942| 0.5693| 0.8984| 0.3961|

| |--------------+-------+-------+-------+-------|

| |STANDARD | .| .| .| .|

--------------------------------------------------------------

EMIT NORMAL - CLEAN ACTUAL TIER CLASS

--------------------------------------------------------------

| | P |

| |-------------------------------|

| | THC | NMHC | CO | NOX |

| |-------+-------+-------+-------|

| | PROB | PROB | PROB | PROB |

|----------------------------+-------+-------+-------+-------|

|ROAD |FACTOR | | | | |

|-------------+--------------| | | | |

|ART/FWY |ROADTYPE | 0.0046| 0.0050| 0.0006| 0.0000|

| |--------------+-------+-------+-------+-------|

| |VEH_TYPE | 0.0016| 0.0404| 0.0031| 0.0012|

| |--------------+-------+-------+-------+-------|

| |STANDARD | 0.0000| 0.0000| 0.0000| 0.0000|

--------------------------------------------------------------

EMIT HIGH - CLEAN ACTUAL TIER CLASS

--------------------------------------------------------------

| | P |

| |-------------------------------|

| | THC | NMHC | CO | NOX |

| |-------+-------+-------+-------|

| | PROB | PROB | PROB | PROB |

|----------------------------+-------+-------+-------+-------|

|ROAD |FACTOR | | | | |

|-------------+--------------| | | | |

|ART/FWY |ROADTYPE | 0.1236| 0.1307| 0.3307| 0.0000|

| |--------------+-------+-------+-------+-------|

| |VEH_TYPE | 0.5942| 0.5693| 0.8984| 0.3961|

| |--------------+-------+-------+-------+-------|

| |STANDARD | .| .| .| .|

--------------------------------------------------------------

GLM P-VALUES FOR MODELS WITH NO SPEED INTERACTIONS (FROM FACVEHA.SAS)
DRAFT M6.SPD.002h 80 August 24, 1999

Appendix B

Example Application of Speed Adjustment to Exhaust Emissions

The following description is meant as an example of how the basic exhaust emission rates

estimated by MOBILE6 will be adjusted for the effects of average speed and roadway type. The

example will show how the various parts of the overall emission estimate are weighted together. 

It is beyond the scope of this document to explain fully the derivation of the basic exhaust

emission estimates or the weighting factors. The derivation of these distributions are described

in other documents. It is also not the intent of this example to reveal the values for emissions or

weighting factors that are proposed to be used in MOBILE6. All of the values shown in this

example should, therefore, be considered as draft and may not match values shown in other

documents. This should not detract from the value of this example in showing the process of

how the basic emission rates are adjusted for speed.

Basic Emission Rates

For each scenario, MOBILE6 will calculate a basic exhaust emission rate (BER) for two

emission levels (high and normal) for each pollutant for each model year for each vehicle class. 

The basic unit for the BER is the hot running LA4 (with an average speed of 19.6 mph) at

standard operating conditions (i.e., temperature, humidity, etc.). The effect of engine starts on

emissions is calculated separately and is not adjusted for the effects of average speed.

MOBILE6 calculates the emissions for each hour of the day, so the first step is to adjust

the BER for the conditions that affect exhaust emissions. For example, the temperature at 6 a.m.

will be different than the temperature at 1 p.m., so the BER at 6 a.m. will not be the same as the

BER at 1 p.m. after adjustment for temperature. Some adjustments (such as the effects of fuel

sulfur content) will not vary by time of day. Ultimately, there will be 24 values, one for each

hour of the day calculated from the same BER, adjusted for hourly conditions. There will be two

sets of adjusted BER values, one for normal emissions and one for high emitters.

Example Basic Emission Rates

 For this example, we will follow the calculation of NOx emissions from a 1990 model

year passenger car. The calculation would be similar for the other pollutants and other vehicle

classes. This example will not fabricate values for all hours. The calculations will be similar in

all hours, so a single hour example is all that should be required. So, for a given hour, the NOx

emissions (BERs) for our vehicles will be assumed to be:

 0.65 g/mi for normal emitters

 2.10 g/mi for high emitters
DRAFT M6.SPD.002h 81 August 24, 1999

After adjustment, these values must be weighted together by their occurrence in the fleet. 

The number of high emitters will depend on many things (i.e., age, I/M programs, OBD, etc.),

but for our example, we will assume that high emitters are 10% of 1990 model year passenger

cars in this scenario.

Freeway Ramps and Local Roadways

There are four basic roadway types; freeways, arterial/collectors, freeway ramps and local

roadways. The freeway ramps and local roadways can be determined directly from the BER,

since they do not vary with average speed. The freeway ramp and local roadway emissions are a

function of the BER (see Table 13). The NOx BERs we will use (described above) are in grams

per mile units and must be converted to grams per hour. The average speed of the hot running

LA4 is 19.6 miles per hour. For normal emitters, 0.65 grams per mile times 19.6 miles per hour

is 12.74 grams per hour. For high emitters, 2.10 grams per mile times 19.6 miles per hour is

41.16 grams per hour. Using the equation shown in Table 13, the freeway ramp and local

roadway emissions in grams per hour are:

Normal Ramp = 5.353 + 2.863*(12.74) - 0.0101*(12.74)2

 = 40.19 g/hr

Normal Local = 1.870 + 0.701*(12.74) + 0.000609*(12.74)2 = 10.90 g/hr

High Ramp = 5.353 + 2.863*(41.16) - 0.0101*(41.16)2 = 106.08 g/hr

High Local = 1.870 + 0.701*(41.16) + 0.000609*(41.16)2 = 31.75 g/hr

The results will be weighted using VMT and must be converted to grams per mile units. 

The freeway ramp cycle has an average speed of 34.6 miles per hour and the local roadway cycle

has an average speed of 12.9 miles per hour.

Normal Ramp = (40.19 g/hr) / 34.6 mph = 1.16 g/mi

Normal Local = (10.90 g/hr) / 12.9 mph = 0.84 g/mi

High Ramp = (106.08 g/hr) / 34.6 mph = 3.07 g/mi

High Local = (31.75 g/hr) / 12.9 mph = 2.46 g/mi

Since we have assumed that 10% of the vehicles are high emitters, we can now weight the

normal and high emitter results to give a complete freeway ramp and local roadway estimate for

the 1990 model year in this hour.

Freeway Ramp = 1.16* 0.90 + 3.07 * 0.10 = 1.35 g/mi

Local Roadway = 0.84 * 0.90 + 2.46 * 0.10 = 1.01 g/mi

Each hour will have its own basic exhaust emission rate. Since the Freeway Ramp and

Local Roadway emission levels depend on the basic exhaust emission rate, a separate calculation

will be done for each hour of the day.
DRAFT M6.SPD.002h 82 August 24, 1999

Emission Offset

The emission offset (EO) represents the difference between the LA4-based BER and

freeway emissions at 19.6 miles per hour. The values for the EO are shown in Table 14. Since

the BER values lie between the LA4 values (0.591 and 3.245 g/mi) shown in Table 14, the EO

must be calculated using interpolation.

Normal EO = 0.121 + ((0.008-0.121)/(3.245-0.591))*(0.65-0.591) = 0.12 g/mi

High EO = 0.121 + ((0.008-0.121)/(3.245-0.591))*(2.10-0.591) = 0.06 g/mi

An additional emission offset is used for arterial/collector roadways, however this offset

depends on average speed and emissions. These are shown in Table 15. The ratio of the freeway

emission level at each speed plus the arterial/collector offset for that speed, divided by the

freeway emission level at 19.6 miles per hour is the arterial/collector speed correction factor. 

These are shown in Table 17.

Freeway Emissions

Freeway emissions depend on average speed. For each hour of the day, MOBILE6 has a

default distribution of average speeds for freeways. Users will be able to enter local distributions

of freeway average speeds. This is not the same as a distribution of speeds on a particular

freeway.

The MOBILE6 default distribution of average speeds for freeways assumes that there are

many freeways in the area and the distribution represents the average speeds observed from the

different freeways at that hour. The cycles used to develop the speed correction factors each

contain the entire range of vehicle speeds on freeways grouped by ranges of observed congestion. 

So, changing speed in the MOBILE6 model is changing the average speed of the combination of

all vehicles on freeways. MOBILE6 does not effectively model the effect of average speed on

individual vehicles or small groups of vehicles within a single freeway section. If you wish to

model a specific freeway, you would want to reduce the default distribution down to a single,

average speed for the freeway of interest.

In each hour, MOBILE6 will calculate values for each average speed “bin” from 5 to 65

mph in 5 mph increments and for 2.5 mph (14 speed bins) by applying the speed correction

factors from Table 16 to the base freeway emission level at 19.6 mph. The base freeway

emission level is simply the sum of the BER and the adjusted off-cycle emissions (EO). 

Normal Base Freeway Emission at 19.6 mph = 0.65 + 0.12 = 0.77 g/mi

High Base Freeway Emission at 19.6 mph = 2.10 + 0.06 = 2.16 g/mi

There are three sets of speed correction factors in Table 16, one for each of three emission

levels. Both the Normal and High base freeway emission levels we have calculated lie between
DRAFT M6.SPD.002h 83 August 24, 1999

the Level 2 and Level 3 emission levels, shown in Table 16. So the speed correction factor will

be interpolated between the values for Level 2 and Level 3 in Table 16. However, these speed

correction factors do not apply below 7.1 mph. We propose that MOBILE6 will use the

MOBILE5 speed correction factors (See Table 1.6B in AP-42) for speeds below 7.1 mph. For

our example, the NOx speed correction factors for the 1990 model year have A and B

coefficients of 1.456 and 0.926 respectively, where the form of the equation is A/speed + B,

resulting in the following speed correction factors: 

SCF for 2.5 mph = (1.456/2.5) + 0.926 = 1.51

SCF for 5.0 mph = (1.456/5.0) + 0.926 = 1.22

SCF for 7.1 mph = (1.456/7.1) + 0.926 = 1.13

The MOBILE5 speed correction factor at 7.1 mph (1.13) was applied to all emission

levels in MOBILE5. The MOBILE5 speed correction factors will be adjusted to match the speed

correction factors in Table 16 for NOx at 7.1 mph of 2.26, 1.81 and 1.50 for emission levels 1, 2

and 3 respectively by adding the difference to each value.

Level 1 SCF for 2.5 mph = 1.51 + (2.26 - 1.13) = 2.63 

Level 1 SCF for 5.0 mph = 1.22 + (2.26 - 1.13) = 2.34

Level 2 SCF for 2.5 mph = 1.51 + (1.81 - 1.13) = 2.19 

Level 2 SCF for 5.0 mph = 1.22 + (1.81 - 1.13) = 1.90

Level 3 SCF for 2.5 mph = 1.51 + (1.50 - 1.13) = 1.87 

Level 3 SCF for 5.0 mph = 1.22 + (1.50 - 1.13) = 1.58

Using the average emissions for each speed correction factor emission level (from Table

14) of 0.712 and 3.253 g/mi NOx for Level 2 and Level 3 respectively and the predicted base

freeway emission rates of 0.77 and 2.16 g/mi for Normals and High categories, weighting factors

can be derived for interpolating between the speed correction factors. The sum of the two

weighting factors will equal 1.

Normal Level 2 Weighting = (3.253 - 0.77)/(3.253 - 0.712) = 0.978

Normal Level 3 Weighting = (1.0 - 0.978) = 0.022

High Level 2 Weighting = (3.253 - 2.16)/(3.253 - 0.712) = 0.431

High Level 3 Weighting = (1.0 - 0.431) = 0.569

These weighting factors are used to combine the Level 2 and Level 3 speed correction

factors for the calculated base freeway emission case. A new weighted speed correction factor is

calculated for each of the fourteen speed bins for Normals and Highs. For example, the 10 mph

speed bin speed correction factors (using values from Table 16) would be:
DRAFT M6.SPD.002h 84 August 24, 1999

Normal SCF for 10 mph = 0.978 * 1.28 + 0.022 * 1.18 = 1.28

High SCF for 10 mph = 0.431 * 1.28 + 0.569 * 1.18 = 1.22

These speed correction factors are applied to the predicted base freeway emission rates to

determine speed corrected emission rates for each speed bin. For example the speed corrected

emission rates for the 10 mph speed bin would be:

Normal emission level for 10 mph = 1.28 * 0.77 = 0.99 g/mi

High emission level for 10 mph = 1.22 * 2.16 = 2.64 g/mi

Each hour has a default VMT distribution of average freeway speeds that correspond to

these speed bins. The emission rates for each of the bins can be weighted, using this VMT

distribution, to give a composite freeway emission rate. This weighting is repeated for normal

and high emitters, and the two emitter groups can be combined to give an overall freeway NOx

emission rate for 1990 model year vehicles for that hour of the day.

Arterial/Collector Emissions

The arterial/collector speed correction factors shown in Table 17 are applied to the base

freeway emission rate calculated for the freeway emission levels. Since the three emission level

groups are identical for arterial/collector roadways and freeways, the same weighting factors are

used to interpolate between the speed correction factors. For example, the 10 mph speed bin

speed correction factors (using values from Table 17) would be:

Normal SCF for 10 mph = 0.978 * 1.52 + 0.022 * 1.31 = 1.52

High SCF for 10 mph = 0.431 * 1.52 + 0.569 * 1.31 = 1.40

These speed correction factors are applied to the base freeway emission levels to

determine emission levels for each speed bin. For example the emission levels for the 10 mph

speed bin would be:

Normal emission level for 10 mph = 1.52 * 0.77 = 1.17 g/mi

High emission level for 10 mph = 1.40 * 2.16 = 3.02 g/mi

Since the speed correction factors for arterial/collectors (shown in Table 17) converge

with freeway speed correction factors (shown in Table 16) at higher speeds and below 7.1 mph,

the emission rate for arterial/collectors and freeways will be the same for some speed bins. All of

the speed bins are combined, weighted by the fraction of VMT in that speed bin for that hour. 

The composite arterial/collector emissions for Normals and Highs are combined weighted by

their proportions in the fleet for that model year.
DRAFT M6.SPD.002h 85 August 24, 1999

Areawide Emissions

Once a fleetwide (combined Normal and High), hourly (combined speed bins) estimate is

available for each roadway type (freeway, arterial/collector, freeway ramp and local roadway),

these estimates can be combined in a variety of ways, depending on the needs of the user. If an

areawide, hourly result is needed, the results for the four roadway types can be combined,

weighted by the fraction of VMT for each roadway for that hour. An areawide daily result can be

obtained by combining the hourly results weighted by the VMT fraction for each hour. Although

there are default values for the fraction of VMT for each roadway and the VMT fraction for each

hour, users may substitute their own values.

Composite Engine Start and Running Emissions

The emission rates addressed in this document do not contain the effects of engine starts. 

The effect of engine start on emissions is calculated separately and is calculated in units of grams

per engine start. These emission effects resulting from engine starts are not determined by

roadway type and do not depend on average trip speed. They can, however, be combined with

the running emissions to give an overall exhaust emission estimate.

Since the MOBILE6 model does not include a distribution of the effects of engine start on

emissions by roadway type, the combination of the effects of engine start and running emissions

is best done on areawide (combined roadway) emission results. This can be done on an hourly or

daily basis.

MOBILE6 has an estimate of the average daily vehicle miles traveled (VMT) for each

model year in a given calendar year and a distribution of that average VMT over the day by hour. 

MOBILE6 also has an estimate for the number of engine starts per day and the distribution of

those starts over the day by hour. For a given hour, the grams due to engine starts in that hour are

calculated as:

Grams / Engine Start * Fraction of Starts in the Hour * Number of Starts / Day

This value can be converted to grams per mile by determination of the average number of

miles traveled by vehicles in that hour:

Hourly VMT = Daily VMT * Fraction of VMT in the Hour

Once the effect of engine start on emissions is converted to grams per mile, it can be

added directly to the areawide emission estimate for that hour.

Total Exhaust = Engine Start / Hourly VMT + Areawide Emissions for the Hour
DRAFT M6.SPD.002h 86 August 24, 1999

Similarly, a daily total exhaust emission rate can be calculated. Although there are

default values for the number of daily engine starts, the fraction of engine start in each hour, the

daily VMT and the fraction of VMT in each hour, users may substitute their own values.

A calculation is done for each model year of each vehicle class. These values are

weighted using travel fractions (as is done in MOBILE5) to calculate areawide, daily emission

rates for highway mobile sources.

FTP Emissions

The Federal Test Procedure (FTP) is a special case of vehicle driving. It can be simulated

in MOBILE6 by careful choice of weighting factors for engine start soak time, vehicle miles

traveled and roadway types. Since this case will be of special interest for comparison of

MOBILE6 emission rates to Federal certification standards, we plan to build in the appropriate

weighting factors so that calculation of FTP emission estimates using MOBILE6 can be done

simply and consistently.