RTI International is a trade name of Research Triangle Institute

Peer Review of LDV/ LDT OBD and 

High Evaporative Emission Report

Work Assignment 4-01

(RTI 005)

Technical Memorandum

Prepared for

Kent Helmer & Constance Hart

U.S. Environmental Protection Agency

Office of Transportation and Air Quality (OTAQ)

Washington, DC 20460

Prepared by

Dileep K. Birur & Tony Lentz

RTI International

Research Triangle Park, NC 27709

EPA Contract Number EP-C-08-008

RTI Project Number 0211577.005.001

May 2012
Kent Helmer, Constance Hart

May 8, 2012

Page 2

Technical Memorandum on Peer Review of LDV / LDT OBD 

and High Evaporative Emission Report

Table of Contents

Contents Page

Background ............................................................................................................ 1-1

Description of Review Process ............................................................................ 2-2

Summary of Review Comments............................................................................ 3-8

Appendix-A: Resumes of Selected Reviewers...............................................A1-A11

Appendix-B: Charge Questions........................................................................B1-B4

Appendix-C: Questions and Answers.....................................................................C1

Appendix-D: Cover Letters...............................................................................D1-D3

Appendix-E: Review Reports......................................................................... E1-E11
RTI International is a trade name of Research Triangle Institute

TO: Kent Helmer and Constance Hart, U.S. Environmental Protection Agency, Office 

of Transportation and Air Quality (OTAQ)

FROM: Dileep K. Birur, Tony Lentz, RTI International. 

DATE: May 8, 2012.

SUBJECT: Peer Review of Eastern Research Group’s (ERG’s) “Evaluation of the 

Effectiveness of On-Board Diagnostic (OBD) Systems in Identifying Fuel Vapor 

Losses from Light-Duty Vehicles.”

1. Background

The EPA’s Office of Transportation and Air Quality (OTAQ) has recently commissioned 

a report, Evaluation of the Effectiveness of On-Board Diagnostic (OBD) Systems in Identifying 

Fuel Vapor Losses from Light-Duty Vehicles, analyzing high evaporative (evap) emissions field 

data reported for light-duty vehicles/trucks collected through Denver Inspection and 

Maintenance (I/M) lanes. This study involves comparison of information on OBD evaporative 

system diagnostic trouble codes (DTCs) with Sealed Housing Evaporative Determination 

(SHED) results for the same vehicles. The high evaporation emission data used in the study were 

collected over the past 4 years in the Denver, Colorado area using laboratory and portable SHED 

units and remote sensing devices (RSD) on most 1996 and later vehicles. Data were collected in 

3 different studies: Lipan Participant (LP), Ken Caryl Participant (CP), and Denver 2010 

Participant (DP). The information gathered in these “high-evap” studies allows for a comparison 

to OBD data which were either collected at I/M Stations or in the CDPHE laboratories..

The main purpose of the ERG’s analysis was to evaluate OBD’s ability to identify 

vehicles with elevated evaporative emission levels. The analysis indicated that many vehicles 

with high SHED values (hot-soak emissions ≥ 1 gram per quarter hour) do not have stored 

evaporative DTCs. and were therefore not identified by the OBD evaporative system. 

In support of EPA’s Tier 3 rulemaking, EPA has sought the reviewers’ expert opinion on 

its contractor’s (ERG’s) report of evaporative emission field data and related OBD results for 

light-duty passenger cars and trucks, particularly on the methodology, and the validity of the data 

and assumptions that go into this analysis. RTI International facilitated this peer review and this 

technical memorandum contains documentation of the peer review process of the ERG’s study.
Kent Helmer, Constance Hart

May 8, 2012

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2. Description of Review Process

RTI began the review process on January 28, 2012, which continued for a period of 

approximately 2 months. EPA provided a non-comprehensive list of subject matter experts from 

academia and industry (Appendix B of the Statement of Work, WA 4-01) to RTI, and this served 

as a “starting point” from which we assembled the list of subject matter experts. To ensure that 

the review process was performed in a timely manner, RTI contacted the potential reviewers 

within ten days of submitting the work plan and determined that each expert would be able to 

review the study during the period of performance. RTI selected three independent (as defined 

in Sections 1.2.6 and 1.2.7 of EPA’s Peer Review Handbook) subject matter experts based on 

their expertise and their interest to perform the review in the stipulated time frame. In order to 

make the review process as credible as possible, RTI did not consult the EPA in the final 

selection of the reviewers. Appendix A of this technical memorandum provides the resumes 

obtained from the selected reviewers. 

RTI provided the peer reviewers with the ERG report “Evaluation of the Effectiveness of 

On-Board Diagnostic (OBD) Systems in Identifying Fuel Vapor Losses from Light-Duty 

Vehicles” via email on February 19, 2012. In addition, the peer reviewers were also given a 

“charge letter” prepared by the EPA. The note from RTI sent to the reviewers with the charge 

letter is included in Appendix B of this memorandum.

Upon distributing the review material and charge letter to the peer reviewers, RTI advised 

the peer reviewers to formulate any questions or concerns regarding the review material or 

charge letter in the form of an email correspondence. This process provided the peer reviewers 

the opportunity to discuss any questions or concerns they may have regarding the review 

material provided and the expected deliverables. Any reviewer submitted 

questions/comments/concerns were promptly forwarded to the EPA-WAM and Alternate WAM 

via email. Some of the questions addressed in this process and the answers provided are 

included in Appendix C of this memorandum. 

RTI received two completed reviews from the peer reviewers and forwarded on to the 

EPA by the requested date, March 9, 2012. The third review report was submitted to RTI and 

forwarded on to the EPA on March 20, 2012. The review reports included responses to the 

charge letter and any additional comments or recommendations the reviewers may have had. 

From each review participant, RTI obtained a cover letter stating the reviewer’s name, the name 

and address of their organization if applicable, which review documents/media were received by 

the reviewer and which was actually reviewed and a statement of any real or perceived 

conflict(s) of interest. These cover letters and the review reports are included in Appendices D 

and E, respectively, of this memorandum. 
Kent Helmer, Constance Hart

May 8, 2012

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3. Summary of Review Comments

ERG recently completed its analysis on “Evaluation of the Effectiveness of On-Board 

Diagnostic (OBD) Systems in Identifying Fuel Vapor Losses from Light-Duty Vehicles,” on 

evaluating the effectiveness of Second Generation On-Board Diagnostic (OBD) systems through 

a comparative analysis of evaporative emissions field data (e.g. Lipan Participant (LP), Ken 

Caryl Participant (CP), and Denver 2010 Participant (DP)) collected in the Denver area during 

the past four years. The focus of the ERG report was an analysis of evaporative emissions and 

related data collected on model year 1996 and newer light-duty vehicles equipped with OBD 

systems, specifically to evaluate OBD’s ability to identify vehicles with elevated evaporative 

emissions. Three types of data were used in the analysis: On-board Diagnostic (OBD) codes, 

Modified California Method (MCM) inspection, and Laboratory Sealed Housing for Evaporative 

Determination (LSHED) or a Portable Sealed Housing for Evaporative Determination (PSHED). 

The key finding of the ERG report was that a large number of vehicles with high evaporative 

emissions were not identified by the OBD evaporative system. Additionally, the ERG report 

recommends since the Colorado Department of Public Health and Environment has been 

performing ongoing studies in this area, there could be opportunities in the future to leverage 

their work into further improvement of the preliminary correlations developed in the study. 

The rest of this section gives a summary of the review comments received from the three 

peer reviewers: Rob Klausmeier (de la Torre Klausmeier Consulting), Stephen A. Leydon 

(Georgia Department of Natural Resources, Air Protection Branch), and Stephen J. Stewart 

(Pacific Vehicle Testing Technologies). 

3.1 An Overview of the Reviews

All three reviewers addressed the report’s correlation between results of portable SHED 

tests and the presence of OBD diagnostic trouble codes. One reviewer commented that the 

prescreening analysis carried out using RSD tests was inadequate and therefore, the conclusions 

made in the report are not valid. The other two reviews noted in similar fashion the potential 

shortcomings of the RSD prescreening analysis (additional discussion of the prescreening 

analysis issues are provided in subsection 3.2.1 below), but instead, noted that the RSD 

prescreen, however limited in its ability, provided some validation of the conclusions presented 

in the ERG report. Those reviewers, who felt the prescreening analysis did not jeopardize the 

overall conclusion of the ERG report, suggested that the analysis could be beneficial for future 

evaporative emissions analysis. Specifically, Mr. Klausmeier commented, “the data collected 

and analyzed in this study are inadequate to make these conclusions, and that the report should 

not be released until sampling concerns are addressed.” However, Mr. Leydon stated “the ERG

study also indicates that many OBD II equipped vehicles are emitting at levels identifiable by 

RSD and verifiable using SHED testing.” He further indicated that the study provides valuable 
Kent Helmer, Constance Hart

May 8, 2012

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data regarding the ability of OBD II in identifying the evaporative issues with vehicles. The third 

reviewer, Dr. Stewart expressed similar view that, since the pre-screening was ineffective, it can 

be concluded that the evaporative DTCs are very unlikely to be present if SHED results are low.

3.2 Methodology

This section highlights some of the key issues raised by the review panel regarding the 

methodology employed in the ERG study. On selection of vehicles with “high evap” emissions, 

a prescreening test using a remote sensing device (RSD) was employed to identify vehicles with 

potentially high evaporative emissions. Irrespective of their final conclusions, all the three 

reviewers expressed their concerns on the potential shortcomings of the RSD prescreening 

analysis. Beyond the questionable RSD prescreen, the reviewers either had no comments 

regarding the methodology or minor comments and/or clarifications.

3.2.1 Prescreening

Even though the RSD prescreening was not the primary focus of the ERG report, all the 

three reviewers indicated concerns with the prescreening analysis. Since this was a common 

observation by the three reviewers, their comments are highlighted here. Mr. Klausmeier stated, 

“The report should provide details on the number of vehicles screened by RSD, the fraction of 

the fleet that had high evaporative indices based on RSD, and the ultimate fraction of the fleet 

that received PSHED and OBD tests.” He further believes that the conclusions of the report 

cannot be supported by the limited amount of data; instead “the report can only conclude OBD 

misses 50-70% of the high evaporative emitters as determined by the RSD evaporative index, 

with the sample size caveat.” However, Mr. Leydon assessed the potential shortcomings of RSD 

analysis differently, remarking “...(detection by RSD) is a positive finding for programs that 

continue to perform RSD for program evaluation. It would lend credibility to RSD findings of 

“high emitters” regardless of the results of paired OBD records. This finding provides the reason 

why OBD II equipped vehicles that are flagged as gross polluters by RSD will pass an OBD II 

inspection. This is something we have seen in Georgia in past years.” With the similar inference, 

Dr. Stewart noted “The benefit of this ineffective pre-screen is that the sample did in fact include 

a large number of vehicles that did not have high evaporative emissions, and it is nice to see that 

they also had (almost) no evaporative DTCs.”

3.3 OBD 

The On-Board Diagnostic (OBD) codes indicate system or component malfunctions. The 

second generation OBD (OBD II) system is used to detect the malfunctions that could result in 

emissions above a specified threshold level. In general, each of the three reviewers commented 
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May 8, 2012

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on the OBD systems’ abilities to accurately identify evaporative emission leaks. It should be 

noted that each reviewer provided varying comment(s) with respect to the OBD systems’ 

capabilities to identify evaporative emissions, while all three reviewers agreed that OBD systems 

cannot accurately identify all sources of evaporative emissions. Mr. Klausmeier stated “The 

report should attempt to compare the distribution of diagnostic trouble codes (DTCs) observed in 

this sample with the distribution of DTCs found in vehicles tested in I/M programs.”

Whereas, concerning the failure of some early model year OBD systems to correctly 

identify an evaporative emission point, Mr. Leydon commented “The OBD systems in these four 

early OBD II vehicles did not store an evaporative DTC because they do not have enhanced 

evaporative monitoring. This finding may result in non-enhanced evaporative monitored vehicles 

being given more weight as polluters in modeling due to their demonstrated lack of being able to 

identify high evaporative emissions or even the presence of a fuel cap at all.” He further 

indicated that the OBD tests are valid particularly in the first two studies, since OBD was 

evaluated shortly before the SHED test (or the previous day) and he believes that very few 

vehicles change their emissions status over night. 

Similarly, Dr. Stewart pointed out that though SHED results indicate the total rate of 

evaporative emissions, they cannot detect the source of emissions on the vehicle. He further 

commented that, in contrast, an OBD system tests only specific aspects of the vehicle hardware 

and control system while ignoring all other possible sources of evaporative emissions. 

3.4 SHED Results

Overall, each reviewer commented on the Sealed Housing for Evaporative Determination

(SHED) tests performed in each of the three studies. In general, there were few concerns 

amongst the reviewers concerning the results of the SHED tests. One reviewer felt that “the 

report should present more details on how vehicles were procured for the PSHED test.” Adding 

“information on the year, make and model of vehicles that received PSHED tests would be 

useful.” Mr. Leydon commented on the SHED test results stating “the establishment of the 

PSHED at the Denver facility and correlating the readings to LSHED ensured that, for all 

practical purposes the readings are to be considered the same and was also a great benefit for the 

continuity of the study.”

Dr. Stewart noted that certain evaporative leaks identified by SHED tests will never be 

identified by OBD. This is because OBD systems are limited in identifying vapor leaks of a 

certain diameter size, while SHED tests do not suffer from this limited ability. He noted, “There 

are only two types of evaporative problem that OBD does detect: basic evaporative OBD only 

checks the canister purge solenoid and flow rate; and enhanced evaporative OBD also looks for 
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May 8, 2012

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vapour leaks equivalent to a certain size of hole. So high SHED results caused by liquid leaks or 

tailpipe residuals could never be detected by current OBD evaporative monitors.”

3.5 Modified California Method (MCM)

The ERG report also analyzed the relationship between the results of three high 

evaporative vehicle emission field studies and the Modified California Method. Two of the 

reviewers provided comments on the MCM inspection. Both reviewers believed that the analysis 

would benefit from further investigation. Dr. Stewart stated “... the deductions from the MCM 

tests are also somewhat speculative as well as being subjective. In guessing whether the leak 

should have been detected by OBD, they also assume that the OBD system would have had the 

chance to detect the problem, but this may not have been the case. It would be valuable to take 

the investigation further using an evaporative testing cart to measure vapor leaks rates.” 

Whereas, Mr. Klausmeier believed that the authors of the ERG study should “collect and analyze 

data from California roadside emission tests, and other sources to validate, if possible, the 

assumption that vehicles with high evaporative emissions identified in this study are typical of all 

vehicles with high evaporative emissions”

3.6 OBD SHED Pairing

The central focus of the ERG report was to evaluate the effectiveness of OBD to correctly 

identify vehicles with evaporative emissions which were measured with SHED tests. The ERG 

report matched each vehicle in the three studies with corresponding OBD and SHED tests. 

Overall, the reviewers felt that the matching protocol was effective and valuable to the study’s 

analysis. Mr. Klausmeier was not conclusive on supporting or opposing the OBD SHED 

matching protocol. Dr. Stewart’s review did not offer any specify comments on the OBD SHED 

matching protocols carried out in each of the three studies.

Whereas, Mr. Leydon, in discussing the effectiveness of the matching protocol for the 

“Denver 2010” study, noted that “This group had a 100% OBD/SHED match rate presumably 

because the vehicles were recruited and all tests were performed on location during one visit, 

which is the ideal situation.” Mr. Leydon’s comments suggested that the matching protocol used 

for the “Denver 2010” study is valuable and should be followed in future investigations of “high 

evap” studies. This is reasonable assumption considering that there were, according to Mr. 

Leydon, “No specifics are given provided for the high dropout due to no OBD II readings” in the 

Lipan and Caryl studies.
Kent Helmer, Constance Hart

May 8, 2012

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3.7 REVIEWERS’ RECOMMENDATIONS

Though there are several similarities in the comments made by the peer reviewers on the 

ERG study, each of the reviewers has given different recommendations and follow-on options. 

Mr. Klausmeier offered a couple of suggestions for further investigation and follow up, both of 

which were presented in subsections 3.3 and 3.5. Mr Klausmeier believed that the authors of the 

report should collect and analyze data from “from I/M programs, California roadside emission 

tests, and other sources to validate, if possible, the assumption that vehicles with high 

evaporative emissions identified in this study are typical of all vehicles with high evaporative 

emissions” as well as “attempt to compare the distribution of diagnostic trouble codes (DTCs) 

observed in this sample with the distribution of DTCs found in vehicles tested in I/M programs.”

Whereas, Mr. Leydon was supportive of the ERG study results and suggested “If this 

study is a good indication of real life experience, and it should be, modeling of OBD II vehicles 

without enhanced evaporative strategies should be weighted more than newer OBD II vehicles 

with enhanced evaporative monitoring.” However, Dr. Stewart, regarding the prescreening 

analysis, suggested that, “efficacy of the pre-screen was not the point of the study, and while 

adding additional process, it did not add anything to the value of the results.” While not outright recommending to remove the current prescreening analysis, the reviewer suggested that the 

report would have benefitted by removing the initial prescreening analysis. 

3.8 OVERALL CONCLUSIONS

The reviews of the ERG report performed by the three reviewers indicate that, in general,

that the data collected in the 3 “high evap” studies are valid and adequate enough to substantiate 

the conclusions drawn in the ERG report. Two of the reviewers concluded that the ERG study’s 

conclusions are well-supported by the data, even with certain caveats, while a third reviewer 

believed that the data collected are not adequate enough to support the conclusions of the report.

Mr. Klausmeier concluded that “the data collected and analyzed in this study are inadequate (10 

high emitting vehicles) to make these conclusions [conclusions from the ERG report], and that 

the report should not be released until sampling concerns are addressed.” Mr. Klausmeier 

strongly believed that the report suffers from a number of sampling concerns that are centered on 

the RSD pre-screening analysis. 

However, Mr. Leydon concluded “this study provides valuable data regarding the ability 

of OBD II to identify, or not, evaporative issues with vehicles... If this study is a good indication 

of real life experience, and it should be, modeling of OBD II vehicles without enhanced 

evaporative strategies should be weighted more than newer OBD II vehicles with enhanced 

evaporative monitoring. There appears a strong correlation between vehicle age and emissions 
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and between non-enhanced evaporative strategies and newer OBD II equipped vehicles.”

The third reviewer, Dr. Stewart stated, “the conclusions of the report are substantially 

supported by the data presented, but they do come across as being a little dismissive of the 

usefulness or reliability of OBD data as an input for modeling the evaporative emissions of inuse vehicles.” 

However, similar to Mr. Klausmeier, Dr. Stewart noted that the 10 high emitting vehicles 

that remained in table 3.5 from table 3.3 of the ERG report are “hardly an adequate sample from 

which to draw compelling conclusions.” However, Dr. Stewart also noted “there is some 

suggestion that the OBD evaporative monitor might not be sensitive enough to precisely identify 

when a leak might cause SHED results to exceed 1.0g/Qhr, and it could be that it would only 

detect bigger leaks.” From this comment, it can be inferred that the reviewer seemed to support 

the notion that although the sample size may be small, it is more of a function of the limited 

capabilities of OBD than the analysis carried out in the ERG report. 
A. Appendix A: Resumes of Selected Reviewers

Resume of Panel Participants Page

1. Mr. Rob Klausmeier A1-A2

2. Mr. Stephen A. Leydon A3-A4

3. Dr. Stephen J. Stewart A5-A11
A-1

Rob Klausmeier

dKC de la Torre Klausmeier Consulting

1401 Foxtail Cove

Austin, TX 78704

Telephone: 1-(512) 447-3077

E-mail: delaklaus@aol.com

Education

M.B.A., Business Administration, University of Michigan, Ann Arbor, MI, 1973.

B.S.M.E., Mechanical Engineering, University of Michigan, Ann Arbor, MI, 1973.

Professional Experience

Consultant, de la Torre Klausmeier Consulting, Inc, 1994 to present.

Principal Scientist/Group Leader, Radian Corporation, Austin, TX, 1991-1994.

Senior Staff Engineer, Radian Corporation, Austin, TX, April 1988-1990.

Program Manager, Radian Corporation, Austin, TX, 1984-1988.

Senior Mechanical Engineer, Radian Corporation, Austin, TX, 1977-1984.

Refinery Engineer, Standard Oil of California, Richmond, CA, 1974-1976.

Co-op Engineer, General Motors Corporation, Oldsmobile Division, Lansing, MI,

1967-1972.

Areas of Expertise

Rob Klausmeier specializes in the analysis and implementation of air pollution control 

strategies, particularly strategies for mobile sources. In 1994, Rob formed his own 

consulting company, de la Torre Klausmeier Consulting, Inc (dKC). Prior to this, he was 

employed by Radian Corporation. During Rob's 17 years with Radian and 18 years with 

dKC, he has performed a range of programs with an emphasis on the following:

Development of Air Pollution Control Strategies: 

o Modeling vehicle and stationary source emissions:

 Exhaust emissions

 Evaporative emissions

o Developing control strategies for attainment of the National 

Ambient Air Quality Standards

o Costs and cost-effectiveness evaluations of control strategies

o Training on Mobile Source controls

Emission Controls for Large Stationary Engines: 

o Identification of control strategies

o Emission reduction assessments 
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o Cost effectiveness evaluations of controls for gasoline and diesel 

powered engines.

o Renewable alternatives: Wind, solar, bio-fuels

o Integration of energy storage systems

Inspection/Maintenance (I/M) programs: 

o Assessment of emissions test procedures

 Identification of vehicles with excessive exhaust emissions 

 Identification of vehicles with excessive evaporative 

emissions

o Design of I/M test lanes

o Request for Proposals (RFPs) for I/M programs

o Rules and regulations for I/M programs

o Negotiation of contracts for centralized I/M programs

o Performance audits of I/M programs

o Quality Assurance (QA) Programs - quality control, data analysis, 

program evaluation, acceptance tests

o Cost estimates of I/M programs
A-3

Stephen A Leydon

Georgia Department of Natural Resources

Air Protection Branch

Mobile and Area Sources Program

4244 International Parkway 404-675-6156

Atlanta, Georgia 30354 Steve.Leydon@dnr.state.ga.us

Education

Georgia State University Atlanta, Ga

Bachelor of Business Administration December 1999

Computer Information Systems

Massachusetts Bay Community College Watertown, MA

Associate in Science June 1973

Electronic Technology

Weber State University Ogden, UT

National Center for Automotive Science and Technology 2000 - present

On Board Diagnostic Seminars

Colorado State University Fort Collins, CO

National Center for Vehicle Emissions controls and Safety 1999 – present

On Board Diagnostics and Testing Seminars

Work Experience

Certified Georgia Emissions Inspector since 1981 (Basic Program)

Georgia Dept of Natural Resources Atlanta, Georgia

Vehicle Emissions Testing Coordinator January 2000 to Present

a. Responsible for the revision and update of the Georgia I/M Equipment Specifications 

manual to meet Federal testing requirements and Georgia needs.

b. Responsible for maintaining and updating of the Rules for Enhanced Inspection and 

Maintenance O.C.G.A. 391-3-20 as needed.

c. Interface with equipment manufacturers during the development of Georgia hardware and 

software requirements and after deployment during Phase II and Phase III of the Georgia 

I/M program.
A-4

d. Work closely with the Enforcement section to develop covert auditing procedures, 

processes, and data validation methodology.

e. Support EPD law enforcement activities such as fraudulent testing investigations and 

fraudulent document identification.

f. Interface with other state and provincial agencies performing emissions testing.

g. Work with the Industry Advisory Board to resolve program issues and improve program 

effectiveness.

h. Assist in the development of the Inspector Re-certification Process for the Georgia 

Enhanced Emissions I/M Testing Program.

i. Perform electronic data processing for program evaluation.

j. Review annual Georgia Program Report prior to submission to EPA.

k. Review Biennial RSD Program Evaluation Report created by Georgia Tech Research 

Institute under contract with EPD

l. Work with local and national Federal EPA personnel in developing approved test 

procedures, processes and in testing analysis.

SPX Corporation Kalamazoo, Michigan

Field Service Representative Sep 1977 to Dec1999

m. Perform work and equipment training in testing programs in the following states: 

California, Florida, Georgia, Illinois, Massachusetts, New Jersey, New York, 

Pennsylvania, Texas, and Tennessee.

n. Assist in the development of the initial Georgia inspector certification process and 

training as a manufacturer’s representative.

o. Instruct customers in the operation of State specific TSI/ASM/OBD II testing procedures.

p. Work with the State of Georgia, MCI, Parsons, and Region 4 EPA personnel on the 

successful completion of Phase I and Phase II of the Georgia I/M program.

q. Perform field repair of sophisticated engine diagnostic equipment including Diagnostic 

Equipment, Emissions Analyzers, and Computer Office Equipment.

r. Demonstrated capabilities of products to customers, salesmen, and state personnel.

s. Conducted seminars on new products and instructed new service employees in proper 

use, calibration, and maintenance of multiple product lines.

t. Assisted in setting up the Massachusetts program using ASM/VMAS equipment.
A-5

Stephen J. Stewart PhD., MSc., BSc., P.Eng., CEng., MRAeS

Carrington Lane, Abbotsford, Abbotsford, British Columbia, V3G 2M7.

Telephone: 1-604-556-8260

Email: stejste@shaw.ca

Summary

Dr. Stewart studied Aeronautical Engineering at the University of Bristol, then worked as an 

Airframe Systems Engineer for British Aerospace. He completed graduate work at the University 

of Manchester; in Mechanical Engineering for MSc, and Computer Graphics and Flight 

Simulation for PhD. After teaching Thermodynamics and Fluid Mechanics at Salford for seven 

years he moved to Canada, and has since specialized in vehicle emissions and their control. He 

has extensive experience in motor vehicle emission related air quality issues and in the design, 

operation and evaluation of Inspection and Maintenance programs as well as other emission 

control initiatives. 

He has completed many projects for the British Columbia inspection and maintenance program 

as well as for the Ontario Ministry of Environment, and for Environment Canada. In 2004 he 

travelled to Urumqi, P.R.China to help develop the air quality monitoring, motor vehicle 

emission control and air quality improvement project funded by the World Bank. He is an 

Honorary Research Associate in the Department of Statistics at the University of British 

Columbia.

Dr. Stewart is a private pilot and President of the Abbotsford Flying Club, as well as a Treasurer 

of the Abbotsford International Airshow Society. He is the Canadian representative on the 

Environment Committee of the Guild of Air Pilots and Air Navigators and a member of the 

North American Section Board.

Employment History

Operations Manager, BC AirCare Program 2012 to present

Senior Project Engineer, BC AirCare Program Oct 1994 to 2011

Manager of Emission Testing and Standards (Acting), BC AirCare Program Aug 1998 to 

Dec 1998

Emissions Testing Specialist, BC AirCare Program Apr 1993 - Sep 1994

Honorary Research Associate, UBC Department of Statistics Sep 2000 to present

Instructor, BCIT School of Transportation Apr 1998 to Jun 2003

Instructor, Columbia College, Burnaby, BC Jan 1993 - Apr 1993, 1994 and 1996 
A-6

Continuing Education Instructor, University College of the Fraser Valley Jan 1995 - Mar 1995

Substitute Teacher, Abbotsford School District (#34), BC Oct 1992 - Mar 1993

Consultant to Monodraught Ltd., High Wycombe, England 1988 to 2007

Senior Lecturer, University College Salford, School of Engineering, Salford, England Jan 1986 

- Aug 1992

Airframe Systems Engineer, British Aerospace, Woodford, England Aug 1978 – Aug 1982

Education

PhD. Flight Simulation, University of Manchester Oct 1983 - Dec 1985

MSc. Mechanical Engineering, University of Manchester Oct 1982 - Oct 1983

BSc.(Hons) Aeronautical Engineering, University of Bristol Oct 1975 - Jun 1978 

Project Experience

Automotive Emissions Testing and Repairs 

Light-duty gasoline vehicles

SS reviewed and developed ASM and idle test standards for the BC AirCare program starting 

in 1995. The final version was created in 2000, and is still used for 1991 and older vehicles. 

These standards are a function of vehicle weight for ASM tests, and of engine size for idle 

tests, as well as accounting for vehicle model year. Also implemented in 2000 was reporting 

of average passing readings which give motorists an indication of what is normal for their 

vehicle. These readings were implemented for IM240 as well as for ASM and idle. 

In 1998 to 1999 SS ran two projects to test gas caps on in-use vehicles in BC. In the first 

project the gas caps of vehicles undergoing regular inspection were tested in order to assess 

the incidence of leaking caps on in-use vehicles. This project provided new caps for all 

vehicles that showed any leakage, and the old caps were retained for the second project. The 

second project measured mass flow leakage rates as a function of pressure differential, using 

a custom-built system.

From 2002 to 2008 SS ran a series of projects to establish the efficacy of subsidizing 

emission repairs that would otherwise not be performed because of repair cost limits. The 

projects achieved emission reductions by providing repair subsidies for light-duty vehicles 

that had failed emission inspections, and which would otherwise receive a Cost Waiver. 

Administration of the program required accurate assessment of individual potential benefits 

from diagnostic information, and the specification of appropriate repairs. With these controls 

in place it is a cost-effective policy.
A-7

Working with faculty and graduate researchers in UBC Dept of Statistics during 1999 to 

2001, SS developed a knowledge-based expert system that can assist repair mechanics in 

selecting the repair actions that are most likely to reduce a vehicle’s emissions to below 

allowable I/M maxima. The expert system is based on inspection and repair data collected by 

the British Columbia AirCare I/M program. The system is an observational model based on 

what was done, and appeared to work, in real reported cases. It does not use the type of rulesbased approach which could be developed from a failure modes and effects analysis. Its most 

efficacious implementation is as part of an overall package which also includes this other 

type of information. Access to is via a www interface, and allows its responses to incoming 

queries to be generated from the most up-to-date data available.

From 2003 to 2005 SS develop a method to report CO2 emission rate and fuel consumption 

from IM240 tests. The difficulty is that existing IM programs do not all use a standardized 

test duration or test method and only a mass-emissions test, driven over a specific cycle can 

be considered. The calculation of fuel consumption from the quantities recorded in a 

complete IM240 test is a simple function of the masses of CO2, CO and HC, the carbon 

weight fraction of the fuel, and the distance driven. A problem arises when trying to compare 

results from tests which have fast-passed and have been terminated at different times, 

because the rate of fuel consumption is not constant through a test. So when a test terminates 

early the actual measured rate of fuel consumption could be much less than, or much more 

than the rate that would be achieved if the test had gone to full duration. This project 

developed methods to project full-duration fuel consumption from tests which actually fastpassed.

In 2006 and 2007 SS led a multi-stakeholder team to develop the communications strategy 

and formats for reporting CO2 emission rate and fuel consumption for every vehicle tested 

by the BC AirCare program. The result was successfully implemented in June 2007

From 2007 onwards SS has organised and run vehicle emissions clinics at various locations 

in BC, YT and AB in response to requests by local air quality organizations. These clinics 

introduce motorists to the need for proper emissions maintenance and repair, as well as 

establishing a picture of the in-use emissions performance of vehicles in non-IM areas.

In 2003 SS developed a method that used total exhaust carbon to identify IM240 test 

problems where exhaust was being lost from the sampling system. This enabled invalid tests 

to be identified and aborted when they reached 30 seconds into the test cycle. The method 

was implemented for all IM240 tests in BC in 2004. It saved operational time and avoided 

many errors of omission.
A-8

Light-duty diesels

In 1999 SS created a new transient light-duty diesel test that was implemented by the BC 

AirCare program in 2000. The test used the second phase of the IM240 driving cycle and 

looked for peaks in exhaust opacity. It was subsequently adopted by KOTSA for all diesel 

vehicle inspections in South Korea as a replacement for their lug-down test 

Heavy-duty diesels

In 1996 SS was part of the team that launched the BC on-road heavy-duty diesel inspection 

program. This was the first program anywhere to use the SAE J1667 test. This project 

included everything from specifying, purchasing and commissioning equipment, to policy 

making, establishing a network of independent repair facilities, industry communication and 

liaison, and regular analysis of inspection data after implementation.

In 2010 SS was a member of the industry advisory working group for Metro Vancouver’s 

development of regulations for off-road heavy-duty diesels. These are primarily construction 

equipment.

Analysis of Vehicle Population and Use Data 

In 1996 SS developed a method for assessing in-use annual kilometers travelled from 

odometer readings recorded during annual inspections, and which tracked the readings of 

individual vehicles. Previous estimates were limited by database considerations to comparing 

average values from different calendar years and vehicle model years. SS has used this 

method for all subsequent vehicle annual kilometer estimates.

Starting in 2002 and continuing into 2012 SBA has undertaken a series of analyses for 

Environment Canada Pollution Data Branch to define a detailed fleet profile, by GVWR, by 

fuel type, by model year, for all the vehicles in Canada, separated by jurisdiction and down to 

the level of FSA. The projects have drawn on various available data sources, including 

provincial registration files, Drive Clean data, AirCare/ACOR data, and Polk and DesRosiers 

summary data. From these data sources, the vehicle fleet can be defined by 

province/territory, by Gross Vehicle Weight Rating (GVWR), by fuel type, by model year, 

by postal code, at quarterly intervals from 1980 on. 

In 2000, working with GWT Consulting, SS created an on-board system to log in-use driving 

behavior. The purpose of this study was twofold: to create a driving trace representative of 

typical commuter driving; and to develop better estimation techniques for cold-transient fuel 

use and emissions. Study data was collected from a combination of rental and volunteer 
A-9

vehicles. Collected data comprised vehicle position, elevation, speed and heading 

information from an on-board Global Positioning System (GPS); and a list of vehicle 

parameters extracted from the vehicle data-stream via the On-Board Diagnostics (OBDII) 

connection. This project highlighted the amount of ‘off-cycle’ operation that is included in 

normal driving, and its contribution to overall emissions, with specific emphasis on cold-start 

fuel consumption.

Reporting Emission Reductions 

Since 1995 SS has performed biennial analyses of the emission reductions achieved by the 

BC AirCare program. The first evaluation in 1994 was by dKC and subsequent evaluations 

built on and expanded this initial work. The particular feature of the approach is the use of inprogram data which includes very robust datasets of mass emission data that define the 

emission performance of vehicles that pass and fail the IM tests and those that are repaired. 

The approach and the biennial reports were heavily referenced (although anonymously

because they were not a US source) by Eastern Research Group in their report to the US 

congressional committee on IM program effectiveness reporting in 2004.

Each year since 1999 SS has performed emissions reduction evaluations of the Light-Duty 

Component of Drive Clean Vehicle Emissions Inspection and Maintenance Program. Subsections of this work involve data analysis covering different aspects of the Drive Clean 

program. There are almost 7 million vehicles registered in Ontario, and each year 

approximately 3 million inspections are performed. We have analysed and modeled failure 

rates, effects of program policies, fleet characteristics, repair effectiveness, and program 

benefits. The emission reduction estimates use mass emission factors derived from BC 

datasets.

In conjunction with GWT Consulting since 2001, SS has undertaken analyses of Dive Clean 

heavy-duty diesel test data for input to the malperformance model. The vehicle counts and 

SAE J1667 opacity reading frequency distributions define the probable occurrence of 

different types of malperformance, and these are then related to PM and other emission rates, 

with the overall result being an evaluation of the emission reductions attributable to the 

heavy-duty inspection program.

In 2005 SBA did an evaluation of the suitability of NOx reductions from motor vehicle 

emission reduction projects for use under Ontario Regulation 397/01 which is an emissions 

offset regulation. The overall context was Ontario regulation 397/01 which governs annual 

limits for nitric oxide and sulphur dioxide emissions from the electricity generating sector. 

To satisfy the requirements of these limits a power producer must submit Emission 

Reduction Credits (ERC) which matches actual annual emissions tonne for tonne. The ERCs 
A-10

are derived from reduction projects undertaken by non-regulated facilities and proponents. 

The purpose of this project was to review the potential for NOx emission reductions from 

transportation sources through programs that address human behaviour.

In 2010 SS led a project for Retire-Your-Ride (the Canadian national vehicle retirement 

program) to test the emissions of a 150 scrapped vehicles and compare with the emissions 

from a range of new vehicles that were typical of those being chosen as replacements. This 

project included PM measurements as well as HC, CO, NOx and CO2, and confirmed that 

the claims made for the benefits of vehicle retirement as an emissions reduction approach 

were more than reasonable.

Other Vehicle Emission Reduction Projects

SS did significant work with the BC alternative fuel conversion industry throughout the 

1990s, after uncovering the major problems conversions were experiencing in the inspection 

program. This included writing the BC Alternative Fuel Conversion Policy; a series of 

projects to establish the causes of poor emissions performance and how it could be remedied; 

and ongoing comparison testing for various public fleets. This led to some innovative work 

in conjunction with the Workers Compensation Board of BC and with UBC Environmental 

Health on remediating problems with indoor equipment such as forklifts and ice-resurfacers.

For the Vancouver Airport Authority, in 2005 SS created a simple method to determine 

which taxis qualified for licensing incentives based on their environmental performance.

Selected publications

Society of Automotive Engineers Technical Papers

1. "British Columbia Vehicle Emissions Inspection and Maintenance Program Experience of 

Alternative Fuel Vehicle Conversions" S.J.Stewart, D.I.Gourley, S. Loo SAE 941913

2. "The Certification and Monitoring of Technicians and Repair Centres in British Columbia's 

Aircare Program" S. Loo, S.J.Stewart, D.I.Gourley, SAE 950483

3. "An Evaluation of the Effectiveness of Repairs in British Columbia's AirCare Program" 

S.J.Stewart, S.Loo , D.I.Gourley SAE 950482

4. "Correcting Emissions Problems in Existing Propane and Natural Gas Vehicles in British 

Columbia" S.J.Stewart, D.I.Gourley, S. Loo SAE 952380

5. "Repair Effectiveness Indices for the British Columbia Vehicle Emissions and Maintenance 

Program" S.J.Stewart, S.Loo SAE 961700
A-11

6. "Study of In-Use Alternative Fuel Vehicle Emission Performance under EPA and BC 

AirCare Test Cycles" A.Inglis, C.Prakash, S.J.Stewart SAE 961709

7. "The Development of Advanced Technician Training to Meet the Demands of Enhanced 

Vehicle Emissions Inspection and Maintenance Program Implementation' D.Horrobin, 

R.MacGregor, T.Wood, R.Plett, J.Marchant, S.Loo, S.J.Stewart SAE 961701

8. "A Study of Mileage Accumulation Rates of Light-Duty vehicles in the Lower Fraser 

Valley" S.J.Stewart SAE 961702

9. “Quantification of Evaporative Emissions from Defective Fuel Filler Caps” S.J.Stewart, 

J.Wong, L.Jang, C.Hui, D.Meggy. SAE 2000-01-1171

10. “Cold Start Impact on Vehicle Energy Use” G.W.R.Taylor, S.J. Stewart SAE 2001-01-0221 

“Emissions Performance of In-Use Alternative Fuel Vehicles” J.Wong, D.Gourley, 

S.J.Stewart, SAE 2001-01-3678
12

B. Appendix B: Charge Questions

Particulars Page

1. Letter to Panel Participants with 

Charge questions B1-B4
B-1

TO: Robert F. Klausmeier (de la Torre Klausmeier Consulting, Inc.)

Stephen A. Leydon (SEEN/Georgia DNR)

Stephen J. Stewart (Pacific Vehicle Testing Technologies)

FROM: Dileep K. Birur

CC: Michael P. Gallaher, Tony Lentz

DATE: February 19, 2012.

SUBJECT: Charge Questions for Peer Review of ERG’s study on “Evaluation of the 

Effectiveness of On-Board Diagnostic (OBD) Systems in Identifying Fuel Vapor 

Losses from Light-Duty Vehicles.” 

The U.S. EPA’s Office of Transportation and Air Quality is currently reviewing Eastern 

Research Group’s (ERG’s) draft report on analyzing high evaporative (evap) emission field data 

collected in the Denver area during the past 4 years. The information gathered in the ERG’s 

“high evap” studies and the pretesting studies that preceded them indicated that Inspection and 

Maintenance (I/M) OBD results may have the potential to identify high evap emission vehicles 

through one or more measures of evap emissions. In the ERG’s report, EPA is further 

investigating the possibility that relationships may exist between several different measures of 

light-duty vehicle/light-duty truck (LDV/LDT) evap emissions and the variables that influence 

these emissions. If these relationships exist for evap variables, then they can be used in a 

modeling context to expand EPA’s MOVES predictive capacity for LDV/LDT evap emissions. 

In support EPA’s Tier 3 rulemaking, EPA is seeking the reviewers’ expert opinion on its 

contractor’s (ERG) report of evaporative emission field data and related OBD results for lightduty passenger cars and trucks. Thank you for agreeing to review this report. We are submitting 

this document to you for a peer review of the methodology, and the validity of the data and 

assumptions that go into it. EPA has provided direction and charge questions for this review and 

these are included below. If it is necessary, RTI will arrange a teleconference call so that EPA 

can respond to questions from individual reviewers on the material that was provided for review.

The review will involve a written report that includes the response to the charge questions 

and any additional comments you may have, e.g., margin notes on review materials. Comments 

should be provided in an enclosure to a cover letter that clearly states the reviewer’s name, the 

name and address of their organization if applicable, which model review documents/media were 
Robert F. Klausmeier

Stephen A. Leydon

Stephen J. Stewart 

February 19, 2012.

B-2

received by the reviewer and which were actually reviewed and a statement of any real or 

perceived conflict(s) of interest. Please submit the completed review reports and the signed 

invoice (invoice forms will be sent separately by RTI’s contract office) to RTI by March 05, 

2012. 

The ERG’s report to be reviewed is attached with this letter. Please keep your comments 

confidential until the initial release of the peer review report by the EPA. If you review the 

document as a team, please provide the details of your team members as well. 

Elements to be addressed in the Charge to the Reviewers of ERG’s report: 

“Evaluation of the Effectiveness of On-Board Diagnostic (OBD) Systems in Identifying 

Fuel Vapor Losses from Light-Duty Vehicles.”

The focus of this report is on the analysis of evaporative emissions and related data 

collected on light-duty vehicles equipped with OBDII systems, which are present on 1996 and 

newer model year vehicles. In each of the three high-evap studies (Lipan, Caryl, and Denver, 

2010), many vehicles received measurements relevant to this report. In these three studies, a 

small fraction of these vehicles were successfully recruited as participants, and the remaining 

vehicles were non-participants—the combination of study/participant status producing the three 

separate datasets. The analysis looks to identify any relationships which may link the several 

different measures of evaporative emissions and the variables that influence evaporative 

emissions. If they exist, the report summarizes the evidence for using them in a modeling context 

which may be useful to the development of EPA’s MOVES model.

Correlating tailpipe emission measurements using IM240 tailpipe measurements and the 

OBD system has always been challenging and has been well documented. In this report, the 

relationships which are explored are between the results of high evaporative vehicle emission 

field studies and:

 Onboard diagnostic trouble codes (OBD DTCs); indicate vehicle 

parameters/conditions, including whether vehicle has seen high exhaust or high 

evaporative emission levels. During routine IM station inspections, OBD inspections 

are performed on 1996+ vehicles. OBD codes are discrete variables, with values of 

‘set’ or ‘not set’.

 Portable or laboratory-based SHED results; an assessment of evaporative emissions 

by testing each high-evap vehicle in a SHED (evap emission results are continuous 

variables with units of grams HC/15minutes).

 Modified California Method (MCM) inspection; an under-hood and under-body 

olfactory, visual, and electronic HC-sniffer check, for each high-evap vehicle. MCM 

variables are generally discrete and the inspections provide ‘smell/no-smell’ (noted 
Robert F. Klausmeier

Stephen A. Leydon

Stephen J. Stewart 

February 19, 2012.

B-3

by the inspector), apparent condition of various fuel system and evap control system 

components and ‘detect/no-detect’ by the electronic HC sniffer.

Participant vehicles and non-participant vehicles received different sets of emission tests 

in each of the three studies covered in this report. Non-participants (I/M-compliant vehicles only) 

received RSD measurements and OBD inspections, which reported back diagnostic trouble codes 

(DTCs) for 1996 and newer model year vehicles. Participants (I/M volunteers for high evap 

emission vehicle testing) received, in addition to RSD and OBD measurements, a measurement 

of evaporative emissions by placing the vehicle in a SHED. In the Lipan and Ken Caryl studies, 

a portable PSHED was used. In the Denver 2010 study, a portable SHED was used for the 

vehicles tested at CDPHE’s West Tech Center and a laboratory SHED was used for vehicles 

tested at CDPHE’s Aurora test facility. Participants also received MCM inspections.

The analysis described below is broken out by:

 Model Year;

 OBD Evap readiness monitor status; and

 Presence of enhanced evap system for 1996-1998 vehicles.

(break-outs were made to the finest level of detail possible; however, this was dependent 

on the sample size for each category)

The three different datasets were used in this study to determine if high evaporative 

emitters, defined by the portable SHED, were appropriately identified by the OBD system on the 

vehicle. The results for this analysis seem to indicate that many vehicles with high portable 

SHED values probably do not have evaporative DTCs set. For vehicles with high values from 

portable SHED testing, ERG attempted to make an assessment of the source of the vapor leak. 

These assessments suggest that about half or more of the high emitters identified should have 

been identified via the OBD system but were not. The preliminary analysis suggests that OBD 

systems were unable to identify 50–70% of the potentially high evaporative emitters in these 

study groups. The lower end of the range, 50%, is based on the known occurrences of when the 

OBD system should have detected the leak from a known source as shown in “technician” 

comments. The higher end of the range, 70%, includes the unknown leak sources which are 

likely to be located in the vapor space of the fuel system, which is too tightly packed for the HC 

sniffer to reach, as opposed to the fuel line connection points or the fuel rail, which are liquid 

leaks and not detectable by the OBD system.

Additionally, the OBD results indicated that vehicles with high portable SHED values 

were likely to have evap DTCs set. However, it was seen that high portable SHED values also 

indicated the likelihood of having an exhaust HC DTC set. Vehicle age was found to be 

insignificant statistically for identifying vehicles with evap codes set, but was significant for 

identifying vehicles with exhaust codes set.

In their comments, reviewers should distinguish between recommendations for clearly 

defined improvements that can be readily made based on data or literature reasonably available 
Robert F. Klausmeier

Stephen A. Leydon

Stephen J. Stewart 

February 19, 2012.

B-4

to EPA and those improvements which are more exploratory or dependent on information not 

readily available to EPA. Any comment should be sufficiently clear and detailed to allow a 

thorough understanding by EPA or other parties familiar with the report. EPA requests that the 

reviewers not release the peer review materials or their comments to anyone else until the 

Agency makes its report and any supporting documentation public.

If a reviewer has questions about what is required in order to complete this review or 

needs additional background material, please direct the reviewer to contact RTI’s project 

manager for this effort. If a reviewer has a question about the EPA peer review process itself, 

please have the reviewer contact Ms. Ruth Schenk in EPA’s Quality Office, National Vehicle 

and Fuel Emissions Laboratory by phone (734-214-4017) or through e-mail at 

schenk.ruth@epa.gov.
C. Appendix C: Questions and Answers Provided During 

the Review Process

Particulars Page

1. Questions and answers provided 

during the review process C1
C-1

Question from Rob Klausmeier to RTI (email dated February 23, 2012): 

The following sentences appear to be inconsistent.

2nd paragraph page 3, 2. 

The results for this analysis seem to indicate that many vehicles with high portable SHED values 

probably do not have evaporative DTCs set.

3rd paragraph page 3, 2.

Additionally, the OBD results indicated that vehicles with high portable SHED values were 

likely to have evap DTCs set.

Could you clarify which statement is correct?

EPA response to RTI to question from Rob Klausmeier (email dated February 27, 2012):

The first paragraph below (with the 50-70%) is the correct charge question. The second one 

doesn't make much sense, as you will see when you read the revised report which was sent.
D. Appendix D: Cover Letters

Particulars Page

1. Cover letter from Mr. Rob Klausmeier D1

2. Cover letter from Mr. Stephen A. Leydon D2

3. Cover letter from Dr. Stephen J. Stewart D3
D-1
D-2
D-3
E. Appendix E: Review Reports

Particulars Page

1. Review Report from Mr. Rob Klausmeier E1-E2

2. Review Report from Mr. Stephen A. Leydon E3-E6

3. Review Report from Dr. Stephen J. Stewart E7-E11
E-1

Review-1 by: Mr. Rob Klausmeier.

To: Dileep K. Birur, RTI International, Inc.

From: Rob Klausmeier, de la Torre Klausmeier Consulting, Inc.

Subject: Comments on the Report “Evaluation of the Effectiveness of On-Board

Diagnostics (OBD) Systems in Identifying Fuel Vapor Losses from

Light-Duty Vehicles”

As requested by RTI, I have reviewed ERG’s report evaluating the effectiveness on- board 

diagnostics (OBD) systems in identifying vehicles with significant fuel vapor losses. I have 

been involved in mobile source evaporative emissions modeling since 1985 and have helped 

many states implement OBD inspections as part of their inspection/maintenance (I/M) 

programs. As a result, I recognize the important consequences of the initial findings of this

report – that OBD systems may not identify a large fraction of the fleet (50-70%) with 

excessive evaporative emissions. This finding affects both state implementation plans with 

regards to the effectiveness of I/M programs and future strategies for phasing out Stage II 

systems and instead relying on on-board refueling vapor recovery (ORVR) systems to control 

refueling emissions. I believe that the data collected and analyzed in this study are 

inadequate to make these conclusions, and that the report should not be released until 

sampling concerns listed below are addressed. My comments are broken into major and 

editorial comments.

Major Comments:

I have several concerns over the sample size and methodology used to procure vehicles for 

this test program and accordingly the representativeness of the test sample. In addition, I 

have concerns over some of the OBD assumptions. Below are my comments:

I recognize the difficulty in identifying vehicles with high evaporative emissions, but 

this reality does not negate the fact that you cannot make a definitive conclusion on 

OBD performance based on 10 high emitting vehicles.

The report should present more details on how vehicles were procured for the PSHED 

test. The report notes that priority was given to recruiting vehicles that had high 

evaporative indices as determined by RSD measurements. The report should provide 

details on the number of vehicles screened by RSD, the fraction of

the fleet that had high evaporative indices based on RSD, and the ultimate fraction of 

the fleet that received PSHED and OBD tests. Information on the year, make and 

model of vehicles that received PSHED tests would be useful.

The report appears to make the assumption that vehicles identified for testing because 

they had high evaporative indices are representative of all vehicles that have high 
E-2

evaporative emissions. The report does not provide evidence that vehicles with high 

evaporative indices based on RSD are necessarily typical of all vehicles with high 

evaporative emissions. For example, vehicles with vapor leaks that do not create a 

hydrocarbon plume while the vehicle is driven but still create significant vapor losses 

during hot-soak and diurnal conditions would not have high RSD evaporative indices. 

As a result, I have concerns over the conclusion that OBD misses 50-70% of the high 

evaporative emitters. Instead, the report can only conclude OBD misses 50-70% of the 

high evaporative emitters as determined by the RSD evaporative index, with the sample 

size caveat.

The authors should collect and analyze data from I/M programs, California roadside

emission tests, and other sources to validate, if possible, the assumption that vehicles 

with high evaporative emissions identified in this study are typical of all vehicles with 

high evaporative emissions.

The report assumes that because the evaporative monitor is ready the OBD system has 

recently checked the evaporative emission control system. After the evaporative 

monitor becomes ready it stays ready until codes are cleared. Because most vehicles, 

particularly older models, have stringent criteria to run the evaporative monitor, a 

vehicle could likely have a problem with the evaporative emission control system, be 

ready, and have the MIL-off (with no DTCs). The OBD system may eventually identify 

the problem, set an evaporative emission DTC and turn the MIL on.

The report notes that some vehicles with high evaporative emissions had exhaust 

related DTCs but no evaporative DTCs. Did ERG investigate the enabling criteria for 

the evaporative DTCs to see if the presence of exhaust DTCs might have kept the 

evaporative monitor from running?

The report should attempt to compare the distribution of diagnostic trouble codes 

(DTCs) observed in this sample with the distribution of DTCs found in vehicles tested 

in I/M programs. In Connecticut, for example, 17% of the vehicles with illuminated 

MILs have evaporative emission DTCs. The top evaporative DTCs in Connecticut (in 

descending order) are P0442, P0455, P0440, P0441, P0446, and P0456. The four 

evaporative DTCs in ERG’s study are P0442, P0443, P0451, and P0457. Only one 

appears on Connecticut’s top evaporative DTC list.

Also, even though it’s not the mission of the report to evaluate the RSD evaporative 

index, the fact that only 29 out of 157 vehicles exceeded the 0.3g/Qhr threshold raises 

concerns about the effectiveness of the RSD based index in identifying vehicles with 

excessive evaporative emissions.

Editorial Comments:

I have provided a marked-up copy of the report that contains editorial comments.
E-3

Review-2 by: Mr. Stephen A. Leydon

TO: Dileep K. Birur (RTI International)

FROM: Stephen A. Leydon

DATE: March 18, 2012

SUBJECT: Review of “Evaluation of the Effectiveness of On-Board Diagnostic

(OBD) Systems in Identifying Fuel Vapor Losses from Light-Duty

Vehicles” Version 9 dated February 17, 2012

This is an evaluation of Eastern Research Group’s (ERG’s) final report on evaluating the 

effectiveness of Second Generation On-Board Diagnostic (OBD) systems through a comparative 

analysis of evaporative emissions field data collected in the Denver area. 

Several studies were performed through Cooperative Research and Development 

Agreements between the Assessment and Standards Division (ASD) within the Office of 

Transportation and Air Quality (OTAQ) of the United States Environmental Protection Agency 

(EPA) and the Colorado Department of Public Health and Environment (CDPHE), with support 

provided by ERG. Data was collected at the Denver, Lipan, and Ken Caryl Inspection and 

Maintenance (I/M) lanes using a Portable Sealed Housing for Evaporative Determination 

(PSHED) and remote sensing devices. Because the studies took place at existing I/M lanes, 

OBD information was also available for each vehicle.

The efforts span a four-year span covering 2008 – 2011 at three locations in and around 

Denver, Colorado as noted above. Since the CDPHE operates IM240 lanes capable of capturing 

exhaust gas readings and perform OBD II tests on 1996 and newer vehicles it was beneficial to 

also gather evaporative emissions on participating vehicles as well. These locations were also 

able to perform “SHED” testing which provided a unique opportunity to perform and gather data 

for this study. Since OBD II vehicles are equipped with constant-monitors and enhanced fuel 

metering systems the tailpipe emissions are extremely low by design. However, “vehicle 

emissions” don’t come exclusively from the tailpipe of the vehicle but from a variety of sources. 

OBD II equipped vehicles are designed to monitor some potential non-tailpipe emission points 

such as fuel vapor leaks from the fuel storage system. When an OBD vehicle senses a possible 

leak in the vapor system the malfunction Indicator Light (MIL) is required to illuminate to warn 

the driver of the problem. In response to the MIL illuminating, the driver is supposed to effect 

repairs to correct the problem causing the elevated emissions. For the purpose of these studies it 

is fortunate that not all motorist pay attention to an illuminated MIL. If the illuminated MIL 

were heeded as expected by EPA, then none of the vehicles in the first two studies would have 

arrived with active DTCs. The responsive motorist with an illuminated MIL however may be the 

reason so few participating vehicles had any DTCs.
E-4

In the analysis section the assumptions regarding the OBD tests in the first two studies 

that were taken shortly before the SHED test or the previous day are valid in my opinion since 

very few vehicles change their emissions status over night. In the first two studies the OBD was 

evaluated up to a day prior to the SHED testing. With OBD, however the MIL can illuminate on 

the next key cycle after an OBD evaluation has been performed but that does not mean that the 

emissions just exceeded the limits. In many cases the emissions have been elevated for up to 

several key cycles prior to the illumination of the MIL. No mention was made that any 

participating vehicle had the MIL off during the OBD II evaluation but illuminate after the OBD 

test during the SHED test(s).

The “Denver 2010” repair effectiveness study indicates 68 vehicles were recruited using 

RSD measurements around Denver. This document does not specifically state that the vehicles 

recruited by mail had very high RSD readings and were considered “gross polluters” or what 

threshold was the determining factor for selection but it does not make sense that “clean 

vehicles” would be solicited for the repair study. This group had a 100% OBD/SHED match rate 

presumably because the vehicles were recruited and all tests were performed on location during 

one visit, which is the ideal situation. The establishment of the PSHED at the Denver facility 

and correlating the readings to LSHED ensured that, for all practical purposes the readings are to 

be considered the same and was also a great benefit for the continuity of the study. 

Review of the timeline of the several studies and the number of “dropped” tests indicates 

that as each study was completed and analyzed that lessons were learned and improvements were 

made before beginning the next study. These adjustments allowed all tests in the Denver 2010 

study to be paired. This important due to the costs of performing the study of each vehicle in a 

study in terms of man-hours, expenses, and other costs not producing an end product. The 

summary in table 3-1 illustrates the point very well since the first set of data had a 29% dropout 

rate. This was cut in half in the following study to 14.6%, followed by a 0% dropout rate in the 

last (Denver) study.

Table 3-2 is an interesting study in the further filtering of questionable data. The percent 

of participating vehicles with the specific evaporative monitor ready was 95% (149/157). This 

high percentage of a “ready” is interesting to me given the mix of older vehicles in the study. It 

is widely accepted that the 1996 through 1998 model year OBD II systems did not easily get the 

evaporative monitor to a ready state. As a result the EPA allows up to two monitors to be not 

ready in the 1996 – 2000 model years. In fact vehicle HE-6725 had a faulty fuel cap that was not 

detected even though the monitor indicated it was ready. 

Reviewing the two tables 3-3 and 3-4 the data indicates that if a vehicle is going to 

exceed the 0.3g/Qhr limits then it is very likely to exceed the 1.0g/Qhr as well. Out of 27 

vehicles that exceeded the 0.3g/Qhr 20 also were in excess of the 1.0g/Qhr limit which is 74%. 

Review of the data in these two tables also indicates that 3 out of the 4 vehicles with an 

evaporative DTC were also over the 1.0g/Qhr, which is 75%. The data strongly suggests that if a 
E-5

vehicle is over the 0.3g/Qhr then it will more than likely be over 1.0g/Qhr as well. The data in 

these tables also suggest that if an evaporative DTC is set (MIL on) then the vehicle will 

definitely be exceeding the 0.3g/Qhr threshold and that it more than likely exceeds the 1.0g/Qhr 

as well. This finding indicates that when the OBD II system evaporative monitor is ready and 

has run and finds a problem (sets a code) there are definitely high measurable SHED emissions 

that can also be detected by RSD. This is a positive finding for programs that continue to 

perform RSD for program evaluation. It would lend credibility to RSD findings of “high 

emitters” regardless of the results of paired OBD records. This finding provides the reason why 

OBD II equipped vehicles that are flagged as gross polluters by RSD will pass an OBD II 

inspection. This is something we have seen in Georgia in past years. 

Unfortunately the findings also provide a strong indication there may be many vehicles 

with high emissions where the OBD II system has not identified an issue that it is supposed to be 

monitoring. Some factors to consider here are that the evaporative monitors have a lot of 

enabling criteria that must be met to allow it to “run”. Ambient temperature greatly affects this 

monitor, as does the amount of fuel in the fuel tank. Given the current state of the economy 

many motorists only purchase small amounts of gasoline at each refueling due to the cost. This 

aggravates the evaporative monitor’s ability in particular to become ready since the fuel level 

typically must be at least a quarter of a tank or more to enable the evaporative monitor to become 

ready and run. Another reason the errant emissions identified by RSD and measured by SHED 

testing are not identified by OBD II is that some emissions are due to leaks in systems not 

monitored or by liquid leaks such as oil, fuel, and high VOC content washer fluid (Atlanta 

Georgia has such a restriction). 

In the evaluation report there is mention that 1981 and newer vehicles were asked to 

participate in at least some of the studies (Lipan, Caryl). OBD II vehicles began with 1996 

model year. This difference in model years could be the reason why so many vehicles had no 

OBD readings to pair with SHED data, a loss of 29% and 14% in Lipan and Caryl studies. No 

specifics are given provided for the high drop out due to no OBD II readings, but this would 

certainly account for the high number. The RSD identified vehicles in the Denver study had a 

0% drop out due to non-pairing presumably due to only 1996 and newer vehicles being sent 

recruitment letters. 

Reviewing comments by inspectors performing the MCM two specific vehicles. Both 

LIP-254 and CRL-568 have the comment “Gas cap IM failure.” In addition, HE-6725 has the 

comment “Gas cap was cause of leak.” These comments infer that a fuel cap pressure test was 

used to determine the gas cap leak failure. No mention in the study is made with regard to the 

use of a separate fuel cap integrity test however 1975 and newer vehicles have this check done in 

Colorado according to information found on the OBD Clearinghouse website. If this is the case 

then only three vehicles had a leaking gas cap and one gas cap was missing (HE-6702) out of 

180 vehicles. The OBD systems in these four early OBD II vehicles did not store an evaporative 

DTC because they do not have enhanced evaporative monitoring. This finding may result in 
E-6

non-enhanced evaporative monitored vehicles being given more weight as polluters in modeling 

due to their demonstrated lack of being able to identify high evaporative emissions or even the 

presence of a fuel cap at all.

Observing the results of the High and Low SHED Pairs data in table 3-6 it becomes 

apparent that newer vehicles (2004 and newer) have a definite ability to control evaporative 

emissions better than earlier years. This may be in part to lower mileage and partly due to 

manufacturers getting better at sealing fuel fittings. Older enhanced evaporative OBD II vehicles 

(2000-2003) show a fairly low number of high value pairs (10% - 14% over .3g/Qhr) while, as 

expected the oldest OBD equipped vehicles have the highest SHED numbers (50% over 

.3g/Qhr). This data also indicates a high number over 1.0g/Qhr for the older OBD II vehicles 

with limited evaporative monitoring. This table illustrates the older OBD II vehicles 

certainly are the ones most likely to be the vehicles identified by RSD and as a percentage of 

their model year have a large amount of evaporative leaks undetected. As a group, the older 

OBD II vehicles contribute more evaporative emissions than newer and should be given a higher 

weight when calculating emissions from the fleet. Not all OBD vehicles were created with the 

same abilities to monitor the various systems, which is an understatement, but the reality is that 

there are tens of thousands of early OBD II vehicles without enhanced evaporative strategies still 

operating on the highways. These vehicles are contributing to higher levels of ambient 

emissions wherever they travel.

These studies were performed in an area that has had I/M testing for many years, as a 

result, the motoring public is well aware that vehicle maintenance is important in order to pass an 

emissions test. Motorist, therefore are more likely to maintain their vehicles especially when out 

of warranty. Since motorist in the study area are very likely to maintain their vehicles 

expectations that if this study were duplicated in a non-I/M venue the results would show much 

higher percentage of >1g/Qhr and >0.3g/Qhr vehicles than were identified here. This study 

provides valuable data regarding the ability of OBD II to identify, or not, evaporative issues with 

vehicles. What is very positive is that if the MIL is illuminated with an evaporative DTC it is 

broken and does have high emissions. 

This study also indicates that many OBD II equipped vehicles are emitting at levels 

identifiable by RSD and verifiable using SHED testing. For whatever reasons there are high 

emitting OBD II vehicles the facts indicate there may be significant emissions coming from 

vehicles assumed to be very clean by federal and state agencies using statistical modeling. If this 

study is a good indication of real life experience, and it should be, modeling of OBD II vehicles 

without enhanced evaporative strategies should be weighted more than newer OBD II vehicles 

with enhanced evaporative monitoring. There appears a strong correlation between vehicle age 

and emissions and between non-enhanced evaporative strategies and newer OBD II equipped 

vehicles. 
E-7

Review-3 by: Dr. Stephen J. Stewart

Evaluation of the Effectiveness of On-Board Diagnostic (OBD) Systems in Identifying Fuel 

Vapor Losses from Light-Duty Vehicles

FINAL REPORT Version 9

Contract No. EP-C-06-0-80

Work Assignment 5-10

Prepared by: Eastern Research Group

February 17th 2012.

Comments by S.J. Stewart March 5th 2012.

Issue

The issue of interest here is whether it is possible to use real-world OBD data regarding the 

evaporative emissions performance of in-use vehicles as an input to inventory modeling. One 

commonly available source of data is the OBD data from I/M programs. But can this data 

provide a direct indication of the evaporative performance of in-use vehicles? For this study the 

measure of actual evaporative performance was SHED (or PSHED) testing. Its results are on a 

continuous scale; however in this study they were divided into just ‘high’ and ‘low’, but with 

two different cut-points between the designations. The OBD results are simpler in that they are 

‘yes/no’ data; either there were evaporative trouble codes, or there were not. So the question 

comes down to the correlation between ‘high/low’ on the SHED results and ‘yes/no’ on the 

presence of evaporative trouble codes. 

Pre-Screening

The first thing to note is that participant vehicles were screened using RSD, so that only those 

likely to have high evaporative emissions participated. So the study tells us nothing about the 

prevalence of OBD evaporative trouble codes in vehicles that were deemed unlikely to have high 

evaporative emissions. The data do show that all participants with evaporative DTCs did have 

high SHED results, but that is simply to be expected if the pre-screen was effective. This leaves 

wide open the question of whether an OBD evaporative DTC is a good indicator of high 

evaporative emissions. 

Because DTCs are not cleared until 40 warm-up cycles have occurred without re-occurrence of 

the problem indicated by the DTC, there is clearly a possibility that the presence of an 

evaporative DTC does not indicate a current evaporative problem, but only that one did exist at 

some recent time. For this study the pre-screen sought to ensure that only high evaporative 

vehicles were likely to participate, and only ‘hard’ DTCs (with MIL on) were considered. Future 

investigations might also include vehicles that would have been screened out from this study, 

and also those with ‘pending’ evaporative DTCs. 

The RSD pre-screen does not appear to have been very effective. Out of 149 cases shown in 

Tables 3.3 and 3.4, only 27 had evaporative emissions over 0.3g/Qhr, and only 20 were over 
E-8

1.0g/Qhr. So only about one in six, or one in seven were correctly screened by the RSD-based 

index. The benefit of this ineffective pre-screen is that the sample did in fact include a large 

number of vehicles that did not have high evaporative emissions, and it is nice to see that they 

also had (almost) no evaporative DTCs.

SHED vs. OBD

SHED results indicate the total rate of evaporative emissions from a vehicle but tell us nothing to 

help pinpoint where on the vehicle is the source of those emissions. This is in complete contrast 

to OBD systems which test only specific aspects of the vehicle hardware and control system, and 

thus completely ignore all the other possible sources of evaporative emissions. 

There are only two types of evaporative problem that OBD does detect: basic evaporative OBD 

only checks the canister purge solenoid and flow rate; and enhanced evaporative OBD also looks 

for vapour leaks equivalent to a certain size of hole. So high SHED results caused by liquid leaks 

or tailpipe residuals could never be detected by current OBD evaporative monitors. 

Modified California Method

The study used the Modified California Method in an attempt to identify what might be the 

causes of poor correlation between SHED-high/low and OBD-yes/no. The MCM inspection tried 

to identify the source of the emissions, and also made a subjective assessment of whether the 

OBD system should have been able to detect the problem. The assessment is based on a nonintrusive investigation, which often did not pinpoint the source of evaporative emissions, so it is 

not certain that only vapour leaks were included – some cases may have been small liquid leaks 

into inaccessible locations, and from the comments it appears that in some cases the source could 

have been residual vapours from the exhaust system. So the deductions from the MCM tests are 

also somewhat speculative as well as being subjective. In guessing whether the leak should have 

been detected by OBD, they also assume that the OBD system would have had the chance to 

detect the problem, but this may not have been the case. It would be valuable to take the 

investigation further using an evaporative testing cart to measure vapour leaks rates. 

Readiness

The issue of readiness is described in the report, and the focus of the results is on cases where the 

evaporative monitor was reported ‘ready’. Experience with OBD data from the British Columbia 

I/M program indicates that the evaporative monitor is the one that is most unlikely to be ‘ready’ 

when a vehicle is presented for inspection 1, and it can also be the most difficult to reset after 

codes are cleared 2. However, I/M programs have ‘readiness criteria’ which allow for one or 

more monitors to be ‘not ready’ at the time of inspection, and therefore I/M programs do not do 

 

1 In 2011 in BC there were 252,497 vehicles that received OBD inspections, from model years 1998 to 2004. The number where 

the evaporative monitor was ‘not ready’ was 46,650, or 17.7% of the total. The rates of ‘not ready’ for the other noncontinuous monitors were CAT 9.4%; OXY 5.3%; HOXY 2.8%; EGR 6.0%

2 When vehicles returned for re-inspection the EVAP monitor was not ready in 7,591 cases out of 14,537, which is 52.2%.
E-9

much to ensure that evaporative monitors ever do actually run. For those vehicles where the 

evaporative monitor has not run, the OBD data is obviously unable to offer any clue as to the 

vehicles likely evaporative emissions. 

Another aspect of readiness is pertinent to this study, in that once a monitor is set to ‘ready’ it 

will stay that way until the system is cleared using a scan-tool or power is removed. The monitor 

will only run when the right conditions are met, and this might not be very often. It could be that 

the evaporative monitor ran at some considerable time in the past and did not detect any 

problems; so it set its own status to ‘ready’ and stored no trouble codes. In the time since the 

monitor’s readiness was recorded, a leak may have developed, but unless the enabling criteria 

were met, the monitor would not have run, and thus would not have even tried to detect the 

problem. In this case it is not valid to say that the OBD system should have detected the problem.

Results

Considering Tables 3.3 and 3.4; the four vehicles with evaporative DTCs did all have SHED 

results over 0.3g/Qhr, and three of them were over 1.0g/Qhr. So none of them were below 

0.3g/Qhr. However, from the 149 participants, 129 vehicles were below 1.0g/Qhr and 122 were 

below 0.3g/Qhr, even though the pre-screen criteria sought to only include vehicles likely to 

have high evaporative emissions. This does not really support belief in the ability of the prescreening system, using RSD, to identify probable high evaporative emitters. 

One striking thing about the results presented in the report is how few vehicles made it from 

Tables 3.3 and 3.4 into Table 3.5. after eliminating cases where the evaporative monitor was 

‘not ready’; cases of 1996-1998 vehicles that only had basic evaporative monitoring; and liquid 

leakers, only ten cases remained from the twenty shown in Table 3.3; and only three of these had 

evaporative DTCs. This is hardly an adequate sample from which to draw compelling 

conclusions. Those three that had evaporative DTCs did have significant evaporative emissions, 

and the four vehicles with the lowest SHED results did not have evaporative DTCs, so there is 

some suggestion that the OBD evaporative monitor might not be sensitive enough to precisely 

identify when a leak might cause SHED results to exceed 1.0g/Qhr, and it could be that it would 

only detect bigger leaks. There are also the potential problems already described pertaining to 

when the monitor last ran, and these may also explain something about the three vehicles in the 

middle, where there were no evaporative DTCs but yet the SHED results were over 6 g/Qhr. It 

is also pertinent that two cases without evaporative DTCs did have other DTCs, and their 

presence may have blocked the evaporative monitor from running. This would definitely have 

been the case with the Toyota Camry because one of the evaporative monitor’s enabling criteria 

is for the MIL to not be commanded ‘on’. For the 1997 Mercury Villager, Alldata does not list 

any possible evaporative DTCs, which casts some doubt on whether this was in fact an enhanced 

evaporative OBD vehicle. 

Conclusions
E-10

The conclusions of the report are substantially supported by the data presented, but they do come 

across as being a little dismissive of the usefulness or reliability of OBD data as an input for 

modeling the evaporative emissions of in-use vehicles. It is clear that they should only be one of 

a number of inputs. In truth OBD only tests a limited number of specific things, and only when 

other specific conditions are met. 

The MCM inspectors’ opinions regarding whether or not OBD should have detected a fault have 

very little value because they neither hunted down the exact source of leaks nor knew when the 

evaporative monitors had last run. 

The sample that made it through to Table 3.5, does suggest that evaporative DTCs are an 

indicator of high evaporative emissions, but the number of cases that did not make it into Table 

3.5 demonstrates that there are also other, very significant causes of high in-use evaporative 

emissions. 

It would be tempting to conclude that when evaporative DTCs are present they do always 

indicate high evaporative emissions. Although this seems probable, the pre-screening criteria for 

participation in the study should have precluded that conclusion. But the pre-screening was 

ineffective and therefore does allow the conclusion that evaporative DTCs are very unlikely to be 

present if SHED results are low. 

The SHED results clearly indicate that the pre-screening from RSD results is not a reliable way 

to identify vehicles that have high evaporative emissions. The efficacy of the pre-screen was not 

the point of the study, and while adding additional process, it did not add anything to the value of 

the results.

The small final data set of cases shown in Table 3.5 is really too small. Further work is necessary 

to enlarge this data set. The value of the data would be enhanced by improving on the MCM in 

order to be more precise regarding the source of emissions, and by removing the confusion of an 

ineffective pre-screen.

Other Points

There are some typographic, grammatical and other errors in the report.

Page 5, 1st para, last sentence: Needs to mention that P2 codes are also generic and some 

P3s.

Page 6, 2nd para, 10th line. The word ‘likely’ is used as an adverb, which it isn’t. It needs 

to be replaced by ‘probably’. This error also occurs twice in the sentence that starts on the 

14th line of page 17; once in the 6th line of the 1st paragraph on page 18; and at the end of 

the 3rd to last line of page 19.

Page 6, start of section 2.3: 
E-11

Second bullet: Needs to include P2 and P3 codes, and needs to indicate that P2 

codes are generic, as are some P3.

Third bullet: Needs to include P#0, P#9, P#A, P#B and P#C

Page 7, last sentence in penultimate para: Says that the PCM will automatically erase 

codes after three consecutive tests -- but it actually needs 40 warm-up cycles.

Page 8, 2nd para, 3rd line: The word ‘both’ needs to be either moved or removed.

Page 8, 6th line of section 2.5: Needs to include ‘psi’ as the unit for RVP

Page 12, last para: There are also some generic evaporative trouble codes in the P2 and 

P3 ranges.

Page 14, 4th line: ‘does’ should read ‘do’

Page 21, Table 4.1: This table is not really necessary. It only repeats information already 

presented in Table 3.5