United States
Environmental Protection
Agency
Office of Air and Radiation
(ANR-443)
Washington, DC 20460
EPA 420-R-93-006
February 1993
Air
Federal Test Procedure
Review Project: ^ M
Status Report
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Federal Test Procedure Review Project;
Status Report
February, 1993
EPA 420-R-93-006
Certification Division
Office of Mobile Sources
Office of Air & Radiation
U.S. Environmental Protection Agency
DISCLAIMER: Although the information described in this status report has been funded in part by the
United States Environmental Protection Agency, it has not been subjected to the Agency's peer and
administrative review processes. It is being released for information purposes only and could be used in
potential regulation development No official endorsement should be inferred. ^:.; .*;:-,;-
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Ov«rvi«w and Background
The cornerstone of the Clean Air Act (CAA) is the effort to
attain and maintain National Ambient Air Quality Standards .
(NAAQS). Regulation of emissions from on-highway, area, and
stationary sources prior to enactment of the Clean Air Act
Amendments of 1990 has resulted in significant emission
reductions from these sources. However, due to factors such as
the growth in air pollution sources, including dramatic increases
in vehicle miles tr.aveled (VMT), many air quality regions have
failed to attain the NAAQS, particularly those for ozone and
carbon monoxide (CO).
The Clean Air Act, as amended (CAA or Act) contains numerous
provisions that are intended to remedy these continuing air
quality problems. As part of this.effort, Section 20-6 (h) of the
CAA requires the Environmental Protection Agency (EPA) to "review
and revise as necessary" the regulations governing the Federal
Test Procedure (FTP) to "insure that vehicles are tested under
circumstances which reflect the actual current driving conditions
under which motor vehicles are used, including conditions
relating to fuel, temperature, acceleration, and altitude."
The FTP is the test procedure used to determine compliance
of light-duty motor vehicles with federal emission standards.L
The FTP is conducted on preproduction vehicles during the motor
vehicle certification process, used to establish that each
vehicle is designed to comply with the appropriate standards for
its full useful life. It is also used to test production line
and in-use vehicles for compliance with emission standards.
The procedure provides a way to consistently and
repetitively measure concentrations of hydrocarbons, oxides of
nitrogen, carbon dioxide/ and carbon monoxide emissions which
occur when a vehicle is driven over a simulated urban driving
trip.2 The principal elements of the test are designed, to test-'
the evaporative and exhaust emissions under several simulated
situations. Evaporative emissions are tested after heating the
fuel tank to simulate hea€xhg by the sun (the diurnal test) and
again after the car has been driven and parked with a hot engine
(the hot soak test). Exhaust emissions are measured by driving
the vehicle (placed on a dynamometer) on a simulated urban
driving trip under two conditions: with a cold start designed to
'-, The regulations that encompass -the many aspects of the HTP, are generally
contained in 40 :CFR Part. 86, Subparts A and B. . - . . -
: For a', detailed discussion of the development of this cycle," see: Kruse, r.cr.a.l
E., and Thomas A. Huls, SAB Paper #730553 "Development of the federal "rear
Driving. Schedule," 1373. A speed-time trace of this cycle .is contained, i.n-4: :~:
? art 36,-Appendix I... • •••'',' " . . .
' •" '.--' - - 2 - ' ''•••"- ..." .
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represent a morning startup after a long soak (a period of non-
use) and then following a hot start that takes place after the
cold start test while the engine is still hot. The FTP also
encompasses all factors relevant to vehicle testing, such as
fuel, vehicle preconditioning, ambient temperature and humidity,
aerodynamic loss, and vehicle inertia simulations. In addition
to evaporative and exhaust emissions, the FTP is also used in
evaluating fuel economy.
This status report addresses the progress EPA has made to
date in complying with the CAA provision and the status of future
research efforts. The first section, "Areas of Potential
Concern," discusses the four general areas of concern with the
FTP noted in §206(h), the basis for each concern, and the
remedies that have been or are being implemented by EPA to date.
The remainder of this report discusses the research program being
conducted by the Agency regarding in-use driving behavior.
Ar«»» of Potential Conc«rn
It is a basic premise that motor vehicle emission levels
determined through the FTP should adequately reflect in-use
vehicle emissions. If in-use driving modes exist that generate
significant amounts of emissions that are not reflected on the
FTP, then the anticipated benefits from motor vehicle standards
are not being fully achieved.
It is also basic that no test procedure can reasonably
duplicate all in-uae conditions. The overall goal of the
Agency's review of the FTP is to aid in determining whether or
not the'FTP should be modified to reflect in-uae conditions not
currently found in the teat and, if so, what modifications should
be made. To meet this goal it is not enough to simply examine
factors such as ambient temperature ranges, in-use fuel
characteristics, or driving patterns. For example, Qualitative
evidence has existed for years that certain types of actual
driving behavior are not represented on the FTP, such aa high
acceleration rates. However, it would be counterproductive to
modify the FTP unleaa two conditions are met. Firat, the driving
behavior or other condition not represented properly by the FTP.
should contribute a significant amount to motor vehicle
emissions. If it doea not, then modifying the FTP would incur
substantial coata and disruption with little or no air quality
benefit. Second, any modification to-the FTP should be expected
to promote design improvements to vehicles and thereby create
real improvements in controlling in-use emissions. If the
current FTP is already effective in reducing emissions during the
non-FTP driving or other conditions, then modifying the FTP would
again incur substantial costs with little or no air quality
benefit. Even if off-cycle emissions exist that are not properly
controlled by the FTP, it is critical to ensure that FTP
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modifications wiir actually promote:the proper, design
improvements. The Agency believes this approach is a reasonable
way to implement Section 206(h)'s requirements. .
• Section 206(h) of the Act specifically requires that EPA
consider four potential areas of concern: fuel, temperature,
acceleration, and altitude. The Agency has identified.several
•other'potential areas of concern relating to driving, behavior:
speed, cold starts , (frequency and driving behavior), trip length,
time between trips, and road grade..
"l. Gasoline. •
The composition of the gasoline used for the FTP (commonly
referred to as indolene) was established by regulation over 20
years ago.3 While it was representative of in-use fuel at the
time, commercial or in-use fuel properties have changed
significantly since then, in some cases having a major impact on
vehicle emissions, both tailpipe and evaporative.4 Studies
conducted during the 1980' s indicated that vehicles tended to
emit higher emissions using commercial gasoline than indolene,
particularly through evaporative losses. To address this
concern, EPA -established volatility limits for gasoline and
alcohol blends. These regulations capped the allowable Reid
vapor pressure for commercial gasoline during the summer months .
The -second phase of these controls became effective in the summer
of 1992. 5 As a result of these actions, the emissions of a
vehicle fueled with indolene are more representative of the in-
use emissions results of a vehicle fueled with commercial
gasoline. ;...-.-. -.'•". --. , / • . - - . : . :••. ."'.'' ..'--.'- • ' • . '• • .- ' .
' . ... " ' '".--,. ••• ,.„_•""•'."' ": ". . * "' - - - - "-"ft1 * ' * ' .
II; Diesel fuel, -'-r,5: •: .'-•..'l-.'^k; ..-..,-•-.'• .- ' •-.•„ v;.;: •?. ^ :- ..:.-' . .'
The AgencyV has: ^aisO^aken: steps to ;reduc« th* sulfur content
"fu|»i^ F^ -7/
on
' ~ '' ' '
III. Alcohol and other -fuels. - •,.-•"
. The Agency promulgated regulations in 1989 which established
emission standards and test procedures for vehicles fueled with
methanol and proposed similar regulations in 1992 for vehicles
"-! :4-p' CFR Ba-rt'. 86-Section 86.113-94. .' . -.:_ -- V< - ' •
1-Evaporative emissions include diurnal, hot soak, .refueling.,-.and running 1 = 3ses .
':55 FR 23658 ..(June, 11, '• 1.3.90) ,, - . ;. , .-"":.,-r. ' '
<--57;-FR.-l-35'.35- (May""", 1332), .: .--'_. ' - -.•;;-"• ..' • . ,Y '".'' '.-".•'.- .'. - •" '- . ,.'' -
•;;..- . :--"', _.;•;. .-' ;-. ::,^. - _:'•;•_: 4., _ '" ' : ' ;'..."•;• '•:-- '; •"•'••-.•.-•
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fueled with compressed natural gas and liquefied petroleum gases.
At this early stage of alternative fuel development, it is
-mpossible to know what the real-world fuel compositions will be
for any of these fuels when used in automotive applications. In
each of these rulemakings, EPA has avoided adoption of narrow
fuel specifications, specifying instead that test fuels be
representative of typical in-use fuels.
These recent requirements established for in-use fuel appear
in general to satisfy §206(h)'s requirements regarding fuel use
in the FTP. In addition, the Agency is also addressing the use
of representative fuels in the Certification Short Test
rulemaking, for which a proposed rule is expected to be published
in January.
Temperature „,_,_•<.
The FTP is conducted between 68 and 86 degrees Fahrenheit,
and includes a cold start in its driving cycle.7 Vehicle
emissions after a cold start increase at cold«r temperatures as a
richer mixture is employed to ensure sufficient fuel vapor for
combustion'to-occur. In addition, colder temperatures lead to
longer warm-up times. This is not a major concern for ozone,
which is primarily a summertime phenomenon, but it is for CO.
Most CO exceedances occur from December to March and over half
occur at temperatures below 45 degrees Fahrenheit.
To reduce the emissions generated from motor vehicles during
cold temperature operation, EPA recently issued 20°F CO emission
standards and test procedure. These regulations were issued on
July 17, 1992 and are phased in beginning with the 1994 model
year 8 The regulations also established interim temperature
defeat,device criteria to maintain proportional CO emission
control between the 20 degree standard and the warm temperature
standards. These regulations insure that the Agency's test
procedures properly reflect the impact of temperature on CO
emissions. As the cold CO rules will prevent emission step-
functions just below 68 degrees that could also impact
hydrocarbon (HC) emissions, they will also insure that the FTP is
representative of HC emissions at colder temperatures.
At warmer temperatures the primary emission concern is
increased fuel evaporation. The Agency is in the process of
revising its evaporative test procedures to address a number of
concerns, including temperature. The final regulations are
expected to specify ambient test temperatures of 95°F. These new
test requirements should insure that vehicles can control
evaporative emissions for most in-use events.
The Agency believes that the above FTP changes appear in
An enable scar* is considered to be a "cold" start if it is preceded by a l:r:
uninterrupted scak, such as those starts that .occur after an overrnght 3.a.-.
*-> «•?. 31333 iJuly L~, 1332) .
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general to satisfy §206(h)'s -requirements regarding temperature
conditions in the FTP. ."'".". -.'•'•- ' ^ - .'f '-'••'•' , ; ',-.', .' - ; ' ;
Altitude •'..'.". ': * • •>' : \ v :::'.:' :.
It has long been recognized that at high altitude locations,
if there is no compensation for the lower air density, engines ..
tend to run rich more frequently and emit more HC and^CO
emissions. Virtually.all light-duty vehicles have been required
to meet emission standards, at both low and high altitude without •
adjustment or modification since the 1984 model year. Light-duty
trucks and light-duty vehicles have had separate high altitude
standards since the 1982 model year. Regulations published on
June 5, 1991 will require light-duty trucks to meet emission
standards at both low and high altitude without adjustment or
modification beginning with the 1997 model year.' The.: cold
temperature CO regulations require that both light-duty vehicles
and light-duty trucks meet the standard at both low and high
altitude without modification. The FTP does not specify an
altitude range in which the test.must be conducted. In effect,
the regulations allow the FTP to be conducted at any altitude and
this, in .fact,,, occurs, / :- ..-."'•; • .• - - .".- .
As with fuel and temperature parameters for the FTP, EPA
believes that the above requirements appear in general to satisfy
§206(h)'s requirements regarding altitude conditions in the FTP.
Current technology vehicles have achieved impressive
reductions in emissions during normal operation, primarily due to
catalyst technology development^ Catalyst conversion
efficiencies (i.e. the rate at which HC and CO are oxidized into
carbon dioxide (C02) and water vapor, or oxides o£ nitrogen (NOx)
are reduced to nitrogen and oxygen) in a modern, properly
operating, warmed-up vehicle can simultaneously exceed 98% for
HC, 99%,. for CO anA; 9G% f or NOx, This includes typical-transient
urban traffic^ O^rS^bhVsucibt as that represented -by the FTP._,.__
However, theser simu3^»neous ciitalyst conversion fifficieneies are
only .achieyabl* \w.itS^|i'Jthree-wmy .catalyst in a veryr narrow -range
of fuel/air™ia*ios£^ air requirement
for complete'combustion" ^(called stoichiometry) . Thus>^ modern,
properly operating vehicles are designed to operate at
3toichiom«try" as mucjv as possible during the FTP.
There are two types of operation that make it difficult to
operate""an engine it stoichiometry. The first type of operation
is cold starts. Fuel must be vaporized with air to combust
properly. When the engine is cold there is not enough heat to
properly vaporize the fuel and additional fuel must be added for
proper'operation, , Cold start emissions are- also increased due to
the lack,of conversion activity, in the catalyst until it heats up
'• . 3 6 FR . 25 7 2 4 (June SV 1:
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(little catalyst activity occurs below about 600 degrees
Fahrenheit). Thus, emission rates during cold starts can be 20-
lOO^times the emission rates during stoichiometric operation. In
fact, the vast majority of emissions from modern, properly
operating vehicles on the FTP occur during the first 10% of the
test, before the engine and catalyst have warmed up. Thus an
important question is whether the cold start portion of the FTP
properly reflects the proportion of time vehicles actually spend
in the warm-up mode.
The second type of operation that makes it difficult to
operate an engine at stoichiometry is high engine loads. High
loads on an engine running at stoichiometry can dramatically
increase engine and catalyst temperatures. These elevated
temperatures greatly increase NOx emissions and can cause engine
knocking and/or damage to the catalyst. The performance and
driveability of an engine under high load can be improved by
running with a richer mixture of fuel. Thus, to prevent
overtemperature damage to the catalyst and insure the best
possible driveability and performance, manufacturers often design
their vehicles' to run rich at high loads. While this reduces NOx
emissions, it increases HC and CO by almost the same 20-100 time*
factor as cold start operation. An important question then is
whether a significant amount of high load operation occurs in-use
that is not reflected on the FTP. Due to the nonlinear nature of
the emission rates, this amount of driving could actually be
fairly small and still have a significant emission impact.
There are a wide variety of in-use factors that impact the
amount of time vehicles spend in either a warm-up or high-load
mode. Warm-up factors include distributions of trip length, time
between trips (referred to as "soak time"), ambient air
temperature, initial idle time, and driving behavior. Factors
that can cause high loads on a vehicle include high acceleration
rates, high speeds, road grades, air conditioning operation, or
some combination of factors (such as moderate acceleration up a
moderate road grade). Complicating the assessment is the fact
that different vehicles have very different calibration
strategies. Thus, the impact on emissions of the exact same
driving behavior may vary widely from vehicle to vehicle.
To properly address the emission impact of driving behavior,
very detailed and statistically valid data are needed for both
actual driving conditions and the impact of this driving on
^missions from a wide variety of vehicles. When the CAA was
amended in 1990, very little information was available on any of
*-he driving behaviors or conditions discussed in this section, or
on their emission impacts. It was therefore necessary for EPA tc
conduct a research program on actual driving behavior and the
emissions impact of such driving.
on Driving Behavior
Past qualitative assessments have concluded that the FT?
effectively represents in-use emission reductions from vehicle
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emission standards (i.e. any/off-cycle emissions did notoccur'
with enough frequency to have a significant impact). However;
the larger the baseline emissions, the smaller the impact from
off-cycle emissions. Other CAA mandates such as Tier I emission .:
standards and longer useful life will all serve to reduce'the
baseline emissions measured by the FTP. If adopted, .Tier II ,
emission standards would have a like effect, Thus, any off-cycle
emissions will become relatively more important in the future. ,
The research program undertaken by the Agency is designed both to
quantify any emission impacts from off-cycle driving behavior and
to.provide information needed to determine whether or not EPA
should make regulatory changes to the FTP.
The program developed by the Agency to evaluate driving
behavior contains three basic components. First, to determine
how vehicles are actually driven, an extensive amount of vehicle
monitoring was conducted. This is described in the next
section, "In-Use Assessment of Driving Behavior." Second, the
data from the vehicle monitoring is being analyzed to determine
cycle and trip information and the impacts of different factors
on driving behavior and to develop driving cycles that represent
the complete range of actual driving behavior. This'part of the
program is described in the section., "Analysis of Driving
Behavior Data." The third part of the- program involves assessing
the emission impact of the driving behavior. This is being
pursued both by development of a computer simulation model and by
vehicle testing, as described in the section, "Emission
Assessment of In-Use Driving Behavior." .
Thes« three sections are designed to describe the entire
research program from start to finish. -The final section of this
report('"Status and Plans," identifies which portions of the work
have already been completed, which are currently in progress, and
which are still to be done. It outlines the status of the tasks
discussed in the sections on the research program and sets up a
general schedule for work that has not yet been completed.
In-UM A«9««MMnt of Driving Behavior
Outreach ••" •.-.:'- '"-•..-•'•'''- • " • ' • • "'.-•• ^' .-:'•'
From the start of the FTP study, EPA has made a concerted
effort to inform all interested parties of our plans to evaluate
in-use driving behavior and to solicit input and participation.
The first public meeting was held at the EPA National Vehicle and
Fuel Emissions Laboratory on December 20, 1990 to discuss EPA' s
plans for the FTP study. This meeting was well attended and
generated considerable interest among motor vehicle.. ,
manufacturers. A second meeting was requested by auto
•representatives to allow them to respond to several issues
discussed at 'the initial meeting, In these subsequent meetings,.
the auto manufacturers demonstrated a willingness to work with •
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EPA to ensure a thorough and successful study. As a result of
these meetings, an Ad Hoc Panel on the FTP was formed by the
Motor Vehicle Manufacturers Association (MVMA) and the
Association of International Automobile Manufacturers (AIAM).
As part of the outreach effort for the FTP Study, EPA held
discussions with the State and Territorial Air Pollution Program
Administrators (STAPPA) and the Association of Local Air
Pollution Control Officials (ALAPCO) members during the first
part of 1991. These talks led to the establishment of a
Cooperative Agreement with New York State's Albany Emission
Laboratory (AEL). The agreement called for AEL to conduct vehicle
testing to examine engine and catalyst cool-down temperatures and
their relationship to motor vehicle emissions.
Driving Behavior Data Acquisition
A centerpiece of EPA's approach to the FTP Study is the
examination of how vehicles are operated in the real world. Early
on, EPA reviewed existing data sources on current driving
behavior and' found them deficient for our task. To truly
understand driving behavior EPA felt that it was critical to
collect real-time driving data on a representative sample of
drivers. The MVMA/AIAM Ad Hoc Panel on the FTP supported this
approach and talks were held to discuss a cooperative research
effort. . „,««.,,_
A meeting was held in Atlanta, Georgia in June_of 1991 to
discuss options for conducting surveys of in-use driving
patterns. The meeting included experts from industry,
government, and academia. Two EPA contractors gave presentations
on alternative driving survey approaches. As a result of the
meeting-, EPA concluded that two complementary approaches were
necessary; data were to be collected using both a chase car
approach and an instrumented vehicle approach-.- Each approach is
described below.
The next step was the selection of cities to survey.
Resource constraints limited the surveys to two cities. In
addition, the two driving survey methodologies restricted the
choices for possible cities. For example, to minimize potential
bias in the selection of drivers and vehicles, the instrumented
vehicle study required recruiting drivers from centralized
Inspection and Maintenance (I/M) stations. The chase car
approach dictated that a city possess an up-to-date
transportation network model. These requirements limited the
choices to a. handful of prospective cities. The Agency selected
Baltimore, Maryland and Spokane, Washington. Baltimore
represents a major urban ozone non-attainment area and is within
the Northeast corridor. In contrast, Spokane is characteristic
of a smaller, cold CO non-attainment area.
Additional information on in-use driving behavior has been
collected in Los Angeles, California and Atlanta, Georgia. The
California Air Resources Board (CARS) has utilized the chase car
approach to collect data tn-Los Angeles. The Agency and GARB
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have coordinated activities... from the^'start of the FTPl.Study; the,,,
'CARB chase- car. study closely paralleled EPA's chase; car efforts
and was conducted by the same contractor. • ,
The Atlanta work was done in coordination with EPA's "Air and
Energy Engineering Research Laboratory (AEERL) of, the, Of fice of "
Research and. Development (ORD) . AEERL is conducting research in
Atlanta as part of a long-term project to improve mobile source
emissions inventories and emissions modeling. With financial
support from AEERL, ah instrumented vehicle survey was conducted
in Atlanta during the summer of 1992 using the 3-parameter
dataloggers developed for the FTP study. This study, along with ^ ;
the Los Angeles study, will improve the regional representation
of the original ih-use; driving surveys.
The instrumented vehicle study consists of placing
instruments in individuals' privately-owned vehicles. :
Datalogging devices are mounted inconspicuously under the
vehicle's hood and data are collected for about one week. To
minimize potential sampling bias, drivers are recruited randomly
from centralized I/M stations using a formal / l ; ,
recruitment/replacement protocol. ~ •
To date> a major accomplishment of the FTP study is the
cooperation and support of both MVMA and AIAM. The instrumented
vehicle component of the FTP study in Baltimore and Spokane was a
joint, effort with MVMA and AIAM. After EPA designed the basic
program and established a contract with Radian Corporatibh to
conduct the testing, the MVMA/AIAM Ad Hoc Panel on the FTP
contributed funds and specialized instrumentation to the
contractor to augment our base program. The MVMA/AIAM Ad Hoc
Panel also agreed to allow SPA to manage th« entire d*t*
collection effort. The joint goal was to instrument 144 vehicles
in each city, for a total of 288 vehicles, as described below:
_ '•'.'. ~~*•**• i^t -
-" ~ 100 ~ ' BPJt sponsored 3-param«t«r vehicles
- , »98 * MVMH/AIAM sponsored 3-param«t«r vehicles
9J° _ MVMA/AIAH sponsored 6-param«t«c vehicles
28'a ~ Total
The 3^-frjfcraawiter instrumentation measures vehicle speed,
engine sp««d^ in revolutions per minute (rpm), and manifold
absolute pr*iisur«. The 6-parameter instrumentation also collects
information on coolant temperature, throttle position, and the
air/fuel ratio. The latter instrumentation packages were custom-
designed by each manufacturer. The 3-parameter instrumentation
was developed by Radian Corporation. At the conclusion of the
program,'the 55 3-parameter dataloggers were turned over to EPA
for future use. ' ..••'--•-• .-'- ." • .". "' ' -. ' .- •-- .: : ;- - • ' ';; '. •" •
A pilot study was conducted in Spokane on January 6-10,
1992. Alternative solicitation and incentive strategies were
- -' ""• •. ': ."V:" . " ••";- ' •:.->;--'r/:"--.". ''•-' 10 --•'; •--'•:•'• :;• ::"••:• .-•.-' : .
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evaluated and 4 vehicles were instrumented. Data collection for
the full study in Spokane began February 3 and was completed the
first week of March. The Baltimore study followed, with data
collection completed in early April, 1992. "~
Chase Car Study
The traditional chase car approach typically involves
driving an instrumented vehicle in a manner that simulates the
driving behavior of the vehicle being "chased." The methodology
used by the Agency in this project- is an enhanced version of this
traditional approach. The new chase approach uses a chase car
which is instrumented with a grill-mounted laser rangefinder.
With the laser rangefinder, it is possible to accurately
calculate the speed of a target vehicle without the chase car
having to emulate the target car's driving behavior. The chase
car is driven over representative road routes, which are
generated using a transportation network model. Tho strengths of
this approach are its ability to collect driving patterns data
for a large sample of vehicles and the virtual elimination of the
bias introduced by the drivers knowing that their driving
behavior is being monitored. ""
The laser rangefinder was a modification of a new
technology; a hand-held laser gun used by police for identifying
speeders. Pilot tests of the laser-equipped chase car were
conducted in the summer and fall of 1991. Data collection for
Baltimore study began in November of 1991; the contractor, Sierra
Research, drove a total of 248 routes finishing December 20.
Following enhancements to the laser and other on-board electronic
equipment, Sierra Research carried out the CARB-sponsored Los
Angeles'chase car study in the Spring of 1992. The Spokane chase
car study was completed by the end of July, 1992.
3UEL Research
The current FTP implicitly assumes that all starts are
either "hot" starts (represented by an engine off time of 10
minutes before restart) or "cold" starts (represented by an
overnight soak before restart). However, almost half of all
restarts in-use occur after a soak period of 10 minutes to 4
hours, for which the engine and catalyst may be in intermediate
temperature conditions. The New York State Automotive Emission
Laboratory, under a grant from EPA, conducted testing to study
the effect of soak time and ambient conditions on engine and
catalyst temperatures. To date, AEL has drafted 4 progress
reports which presented results of the testing. This information
will provide insight into the condition of the engine and
catalyst during starts that fall into these intermediate
temperature conditions.
Analysis of Driving B«h*vior Data
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fractions of time spent at high levels of speed, and
acceleration and specific power.
In the chase car study, route measures are similar to the
trip measures given above. In addition, statistics are
calculated on the portion of survey time during which the laser
was locked on a target vehicle . • • •
Several types of summary measures were requested ' from EPA' s
contractors. Measures of location and dispersion (mean and
standard deviation) , minimum, and maximum capture the essential
features of a particular sample. Greater detaiil is found in
frequency distributions and their associated graphical display.
Because of the concern with the emissions impact of non-FTP high
speed, acceleration, and power, the upper percentiles of these
distributions are computed explicitly to support more detailed
study of these "extremes" of driving behavior. Finally, the
combined distribution of speed and acceleration will be tabulated
to enable more detailed study of engine load patterns .
The driving behavior surveys collected or identified
different factors that could influence driving behavior, such as
type of vehicle, location, and road congestion. The summarized
data described above will also be broken down by these factors .
Analysis of these breakdowns enables the assessment of potential
bias as well as the relative influence of measured factors on
driving. For the instrumented vehicle study, criteria needing
examination for impact on driving behavior include;
vehicle age,
vehicle performance,
transmission type,
time of day and week,
• . driver age,
recruitment site, and
observation phase (first day or later) .
Criteria collected by the chase car study needing study include:
road type,
road grade,
road congestion level, and
target vehicle performance type.
Survey BJM
In order to judge possible bias induced by the data
acquisition methodologies, the study includes several types of
comparisons. For the instrumented vehicles, the breakdown by
observation' phase is used to examine: (.1) whether survey
participant driving behavior is influenced by the presence of the
datalogger; and (2) if any such influence diminishes over time.
Another potential concern with the instrumented vehicle data
involves -driver refusal to participate. Drivers of high-
performance or luxury vehicles were less likely to agree to have
their vehicles instrumented. If these drivers and vehicles have
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estimate the difference between emissions predicted by the FTP
cycle and emissions that occur in actual driving. Using either
computer models or dynamometer testing, this assessment requires
the development of one or more driving cycles that are
representative of the real world. The driving survey data
discussed above will serve as the primary input to this component
of the project.
Several approaches to cycle development currently are under
review. These vary considerably in level of subjectivity. One
approach, used in developing the current FTP, is to splice
together segments of real speed patterns that are selected from
the survey data. A final cycle is obtained by matching summary
features of the resulting speed-time trace with those of the full
sample. A virtue of this and related approaches is their basis
in real driving experience that can be reproduced in dynamometer
testing. The choice of segments and matching criteria are
potential difficulties.
A more directly quantitative approach to cycle development
is to generate a vehicle speed-time trace using Morite Carlo
simulation. Simulated second-by-second values are chosen
according to statistical criteria derived from the survey data.
Cycles are subjected to matching criteria in order to screen out
unsatisfactory candidates. This ia likely to b« a more efficient
method of producing different cycles, but these cycles are wholly
"unreal" in comparison to the splicing approach described above.
Emission A»««»»m«nt of In U»« Driving
Approach ' . .
In analyzing data from the in-use driving surveys it is
essential to consider the emissions impact of the real-world
driving patterns that are not represented by th« current FTP
driving cycle. As discussed, above, this requires assessment of
a wide range of driving behavior, factors influencing emissions,
and manufacturer calibration strategies. In order to perform
these large scale assessments, EPA is developing a. computer model
which simulates vehicle emissions over any d«sired driving cycle.
EPA is using the modeling approach because it affords flexibility
in analyzing the emission impact of the driving survey data and
could allow us to conduct a smaller vehicle testing program. A
simulation model will allow the emission assessment of a number
of unedited and/or composite driving cycles over a large number
of vehicles with relative ease. Conversely, a strict vehicle
testing-based approach for an initial assessment of the emission
impact of in-use driving behavior would limit the assessment to a
small number of composite cycles over a relatively small sample
of.vehicles, and would not allow the needed flexibility for the
type of large-scale assessment desired by EPA. Vehicle testing
will be used during the course of the emission assessment effort.
- 15 .-
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' ^, %, ^
in order to validate the results of the computer simulation
model. Contingency testing plans to gather basic emission-impact
information are also, being prepared in case the model proves to
be too inaccurate for qualitative analysis.
The simulation model computes instantaneous fuel and
emission rates based on instantaneous vehicle speed. This model
is currently" being developed as two components, known as VEHSIM
and VEMISS~. -.""_" - -
The VEHSIM component was originally developed by GM and
later-revised by th* Department of Transportation. The VEHSIM
model takes instantaneous (generally second-by-second) vehicle
speed inputs and calculates instantaneous engine speed and load.
Thes* calculations of engine speed and load are performed
vehicle information regarding vehicle aerodynamics,
'a^^-i^^9^i engine accessories stored: in a
'••'-.'''....'' . " .
.'siconi in;;prd*ir':tb'v'cai<^iat^"'fuel'.and'emissipn rates for an
instantaneous engine speed and load.
Upon completion of VEHSIM and VEMISS, these components will
be linked to produce a fully; functioning model capable of
simulating instantaneous fuel and emission rates based on ah
inputted speed/time trace. •
EPA' s~go*I ia tordafeMsaiafrtfi* emisaioi* impact of actxart
,ing behavicriMoa technology that ia available today and will
likely be available i» th«~h«xt few yeara. To thia endr EPA, .
tested_a flMfe of 29 lat» mpdal, current technology^ _ low mileage
vehicles which" eove>r- a broad range of vehicle types (both car and
light truck* . Th* pbActive is to enable BPX to match, the
driving^cbwr*ct«riatica of any vehicle in the driving aurvey
sample with a representative vehicle froa the 29 vehicle fleet.
The Agency has completed the testing and development of
engine map» for each ofVtha 29 vehicles. Currently, EPA is
wbrkirig to cpa^siile the part libraries for theae vehiclea so that
the VEHSIM/VEMISS model: will be able to simulate fuel and
emission ratea using any speed/time trac* input, for each vehicle
' itarm'. Modal'-vi ._
Before the model can be used to confidently assess,: the
emission impact of. in-use driving, a validation of the model must
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be performed. This validation effort is in progress and
currently focuses on the component of the model which simulates
emissions under warm operating conditions. The purpose of the
first phase validation is to assess the accuracy of the warm
model and highlight the refinements necessary to improve the
accuracy of the model. This is being done by comparing the model
output to actual data over a series of test cycles, including the
FTP and a high acceleration cycle. Future validations will
include comparisons of model results to test results run using
new test cycles on a single large-roll electric dynamometer
(which should much more accurately reflect in»use emissions).
Refinements may include improvements to the engine maps, part
libraries, and the model itself. Validation will continue in an
iterative fashion for each vehicle as improvements are made.
Cold Modal Development
Cold start emission simulations also need to be developed to
estimate the impact of cold start driving behavior and soak time.
Aa the cold start simulation will calculate emissions using the
warm engine-out emission maps as the starting point, development
of the cold start module is being sequenced behind the warm
component of the model. Once the warm component is
satisfactorily validated, the cold operation component will be
developed based on existing test data on the 29 vehicles,
integrated into the model, and validated. Upon completion, the
model will be able to simulate fuel rate and emissions for an
entire vehicle trip.
NFRM D4v*lopii!*nt
The Agency will use the analyses described above in
determining whether or not the driving cycle or other aspects of
the FTP should be revised to properly represent vehicle emissions
during actual driving conditions. However, in any proposal to
revise the FTP, EPA would also need to consider various other
issues, including:
— Technology assessment
- Type of revision needed
- Lead time
- Cost and cost effectiveness analyses
The technology assessment includes determining the changes
needed for manufacturers to reduce emissions during the
identified off-cycle condition, the level of reduction achievable
with different technologies and/or calibration strategies, and
the feasibility of making the technology changes. Closely
related issues are cost and lead time, as greater levels of
technology change or added component requirements will increase
the cost of the regulation and, possibly, increase the lead time
needed for manufacturers to implement the changes.
- 17 -
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to
_ .
; would
/. would
i-ei, revisions to th«9
of "the; vast array of historical
th% Impact- on CAFS -and"
andards, It^may be much more cost
to establish a hew cycle and standard :gy
'
- emissions;,:,
^....
^^ ' -• " -
"standard stringency^ co«ts^^ andi benefits
ley^elrof complexity wilt. be .significantly
€he results of jthe;^study in regar^i:^ ^he;::l«OT*i of-
and ther type of driving eheratin the
Status and Plans
'
- arid plana- to
i:re:asortably
Xn: order to keep this outline
pVi^ -, only::y*ry; 'tirie* statements
thii^ section is ;
^i
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pr-ivina Behavior
Assessment
Tasks Completed to Date
Vehicles instrumented:
Spokane - 102 3-parameter
42 6-parameter
Baltimore - 113 3-pa-rameter
37 6-parameter
Atl. (ORD) - 110 3-parameter
Chase car:
Spokane - 249 routes
Baltimore - 248 routes
L.A. (ARE) - 202 routes
Data processed (Baltimore and
Spokane)
Summary statistics defined
1st draft data summaries:
Spokane instrumented veh
Baltimore instrumented veh
Baltimore chase car
Cool-down study (N.Y. AEL):
6 vehicles tested
4 progress reports
29 vehicles mapped:
1990-92, MPI
40-55 steady state points
7 cold start steady state
FTP
Calif, accel cycle
Data cownloaded to PC
Engine torque calcualted
Warm emission module written
(VEMISS)
1st cut evaluation of maps
Work in Progress
Trip definition
Bias analyses/correction
Recovery of suspect vehicles
Process Atlanta data
Phase I warm speed/accel
analysis (inst. veh.)
Trip definition
Torque v«rificaiton
Soakl time emission impact
Compile parts library
Validate warm modeling/maps
. (2 vehicles)
Summarize test data - all veh
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By January, 1993
Complete cooldown analysis (AEL) Begin cold start model , .
Analyze: -~ development . ""' V
Trip length and soak time -Enhance part library data;
Cold start driving behavior Validate VEHSIM/part library
Warm driving behavior methodology
' Compare modal data to VEMISS
..,.-•'.\.-... ' ''••' ^ •'• '-.-' , •'- v -• - •.,':'•. 'predictions " - ' • • • . •
; Assess modeling effectiveness,
. : inc. testing validation
: ; •'*", Develop contingency test plan
By March, 1993
Develop warm driving cycles '. Complie cold start database
Analyze/effects of driving 1st cut warm speed/accel
behavior influences on: emission evaluation
trips and soak time - Compile/validate part libraries
cold driving "" ~ - all vehicles
warm driving
Compile draft of driving
behavior study for review-
Hold public workshop on analysis ''•/..'
of driving behavior study
-" - ' . - " . '*-.'.-.,'""' • ' : • , • - • ' ''- - 1 " • • .' , - ' •• " , ' •" ~^' L •
:•' •'' ''.•.''•;• .•.,..'"' "•'..."•.'..•.'•• J By Ray, 1993 •-'..- • /.. •'. ".,.,•
Publish preliminary technical Validate warm VEMISS/maps on
report; request public rest of vehicles
comment
By S«pt«ab«r, 1993
_ ~ - Complete enhancements to model
" ^ Complete cold start module
Validate model with test data
Assess emission impact of all
driving behavior
By November, 1993
Final study report, including recommendations, ready for internal
Agency review; begin development of an NPRM to revise the FTP or a
notice of intent to not revise the FTP.
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