Envirotest Systems 

5175 Marshall St., 

Arvada, Colorado 80002 

The Colorado Remote Sensing Program 

January – December 2013

September 2014 

Prepared for: 

The Colorado Department of Public Health and 

Environment 

Prepared by: 

Peter M McClintock, Ph.D. 

Applied Analysis 

13700 Marina Pointe Drive #301 

Marina Del Rey CA 90292-9276

pm2pt5@gmail.com
2 

Acknowledgments 

The author wishes to acknowledge the support and input given by a number of individuals and 

organizations. Particular thanks are extended to the following contributors: 

CDPHE for providing many helpful comments and suggestions. 

Drew Rau, Envirotest Program Operations Division and the Remote Sensing unit of 

Envirotest, Tucson for providing data access and operational information. 

 
3 

Table of Contents 

I. SUMMARY .................................................................................................................................................... 5

II. DESCRIPTION OF THE DENVER CLEAN SCREENING PROGRAM ........................................... 8

A. I/M PROGRAM OVERVIEW ........................................................................................................................ 8

B. MEASUREMENT SITES ............................................................................................................................. 13

C. SOURCES OF DATA AND DESCRIPTION OF ELEMENTS ............................................................................. 18

III. SUMMARY OF DATA COLLECTION ................................................................................................ 21

A. MONTHLY COLLECTION ACTIVITY ......................................................................................................... 21

B. MEASUREMENTS BY HOUR OF DAY ........................................................................................................ 21

C. COMPOSITION OF VEHICLES MEASURED ................................................................................................. 23

IV. CLEAN SCREENING PROGRAM PERFORMANCE ....................................................................... 25

A. VEHICLES SELECTED, NOTICES AND REDEMPTIONS ............................................................................... 25

B. CLEAN SCREEN PROGRAM EFFECTIVENESS ............................................................................................ 27

C. GAS CAP EVAPORATIVE EMISSIONS ....................................................................................................... 30

D. HYBRID RSD-LEI VS. 2-HIT RSD ........................................................................................................... 33

V. ESTIMATE OF OVERALL I/M PROGRAM BENEFITS AND CLEAN SCREEN IMPACT ....... 36

A. CONVERSION OF IDLE TESTS TO IM240 EQUIVALENT EMISSIONS ........................................................... 36

B. ANNUAL MILEAGE WEIGHTING .............................................................................................................. 40

C. ANNUAL EMISSIONS REDUCTIONS .......................................................................................................... 41

VI. IM240 PROJECTED EMISSIONS BY MODEL YEAR ..................................................................... 43

VII. RAPIDSCREEN BENEFITS .................................................................................................................. 47

A. GREENHOUSE GAS AND POLLUTANTS FROM CLEAN SCREEN OPERATIONS ............................................ 47

1. RapidScreen Operating Vehicles ........................................................................................................... 47

2. Generators ............................................................................................................................................. 48

3. Calibration and Audit Gases .................................................................................................................. 48

4. RapidScreen Vehicle Emissions Reductions .......................................................................................... 48

B. RAPIDSCREEN VEHICLE OWNER SAVINGS .............................................................................................. 49

VIII. RECOMMENDATIONS ..................................................................................................................... 50

REFERENCES 

APPENDICES 

 A1 COLORADO 2012 TRANSIENT TEST EMISSIONS REDUCTIONS 

 A2 COLORADO 2012 CLEAN SCREEN AUDIT TRANSIENT TEST EMISSION REDUCTIONS 

 B COLORADO 2012 TRANSIENT TEST REDUCTION TONS 
4 

List of Tables 

TABLE II-1 NORTHERN FRONT RANGE ................................................................................................................... 14

TABLE II-2 DENVER RSD SITES............................................................................................................................. 15

TABLE II-2 DENVER RSD SITES CONTINUED ......................................................................................................... 16

TABLE II-3 EL PASO RSD SITES ............................................................................................................................. 16

TABLE II-4 VEHICLE MEASUREMENT INFORMATION ............................................................................................. 19

TABLE III-1 COLLECTION SUMMARY ...................................................................................................................... 21

TABLE III-2 SOURCE OF VEHICLE REGISTRATIONS MEASURED BY RSD .............................................................. 23

TABLE III-3 TYPE OF VEHICLES MEASURED BY RSD WITHIN REGISTRATION JURISDICTION ................................ 24

TABLE III-4 REGISTERED JURISDICTION AND AGE OF VEHICLES MEASURED BY RSD ........................................... 24

TABLE IV-1 VEHICLES QUALIFIED AS MEETING CLEAN SCREENING CRITERIA BY STATUS ................................... 25

TABLE IV-2 NOTIFICATIONS TRANSMITTED TO DOR ............................................................................................. 26

TABLE IV-3 CLEAN SCREEN AUDIT TEST PASS / FAIL STATISTICS ........................................................................ 26

TABLE IV-4 TRANSIENT TEST EMISSION REDUCTIONS FOR 1982-1985 PASSENGER VEHICLES ............................. 29

TABLE IV-5 CLEAN SCREEN EMISSIONS IMPACT FOR TAILPIPE EMISSIONS ........................................................... 30

TABLE IV-6 CLEAN SCREEN IMPACT ON EVAPORATIVE HC EMISSIONS ................................................................ 32

TABLE IV-7 GAS CAP RELATED BENEFIT TONS..................................................................................................... 32

TABLE IV-8 AVERAGE EMISSIONS PER VEHICLE ................................................................................................... 34

TABLE V-1 LOW SPEED IDLE TO IM240 ................................................................................................................. 37

TABLE V-2 HIGH SPEED IDLE TO IM240 ................................................................................................................ 38

TABLE V-3 ESTIMATED ANNUAL MILEAGE IN 2013 ............................................................................................... 40

TABLE V-4 ESTIMATED ANNUAL TONS OF REDUCTION (IM240 AND IDLE TESTED VEHICLES ............................... 42

TABLE VII-1 REDUCTIONS IN GREENHOUSE GASES AND POLLUTANTS FROM RAPIDSCREEN OPERATIONS ............ 47

List of Figures 

FIGURE I-1 AVERAGE IM240 EMISSIONS REDUCTIONS ............................................................................................ 7

FIGURE II-1: TAGEDITTM SCREEN ........................................................................................................................... 12

FIGURE II-2 A: SITE LOCATIONS NORTHERN FRONT RANGE ................................................................................... 17

FIGURE II-2 B: SITE LOCATIONS – DENVER METRO AREA ...................................................................................... 18

FIGURE III-1 MONTHLY RSD MEASUREMENTS ...................................................................................................... 22

FIGURE III-2 MEASUREMENTS BY TIME OF DAY .................................................................................................... 22

FIGURE IV-1 GAS CAP PRESSURE FAILURE RATES ................................................................................................ 31

FIGURE IV-2 AVERAGE INITIAL IM240 EMISSIONS ................................................................................................ 34

FIGURE IV-3 AVERAGE IM240 EMISSIONS REDUCTIONS ....................................................................................... 35

FIGURE V-1 RSD VS. IDLE TEST EMISSIONS .......................................................................................................... 37

FIGURE V-2 RSD VS. 2500 IDLE TEST EMISSIONS ................................................................................................. 38

FIGURE V-3 RSD VS. IM240 TEST EMISSIONS ....................................................................................................... 39

FIGURE VI-1 LDGV HC REDUCTIONS AND REMAINING EMISSIONS...................................................................... 44

FIGURE VI-2 LDGT HC REDUCTIONS AND REMAINING EMISSIONS ...................................................................... 44

FIGURE VI-3 LDGV CO REDUCTIONS AND REMAINING EMISSIONS...................................................................... 45

FIGURE VI-4 LDGT CO REDUCTIONS AND REMAINING EMISSIONS ...................................................................... 45

FIGURE VI-5 LDGV NOX REDUCTIONS AND REMAINING EMISSIONS ................................................................... 46

FIGURE VI-6 LDGT NOX REDUCTIONS AND REMAINING EMISSIONS ................................................................... 46
5 

I. Summary 

The Colorado Department of Public Health & Environment (CDPHE) and the Department of 

Revenue (DOR) have operated an Enhanced Inspection and Maintenance (I/M) program in 

the Denver metropolitan area (DMA) since 1995. Operations for a remote sensing clean 

screening element commenced in 2003. Previous reports, “The Colorado Clean Screening 

Program’ reports for July 2003 – December 2004 and annual reports for 2005-20121 described 

on-road measurement activities and the vehicles exempted from inspection. This report 

covers calendar year 2013. 

The clean screening program uses remote sensing to measure the tailpipe emissions of 

vehicles as they drive by measuring equipment positioned on the side of the road. Vehicles 

that are determined to have low tailpipe emissions are granted an exemption from the I/M 

inspection. Clean screening improves convenience of the I/M program for vehicle owners. 

In order to exempt vehicles from inspection, computer systems and procedures are required 

for administering the program and notifying vehicle owners of their inspection exemption. 

The I/M program is registration enforced and the administration of the clean screening 

program requires the transmission of information among the contractor, CDPHE and DOR 

who manage motor vehicle registrations. 

Rapidscreen provided benefits to vehicle owners of $5.1M through reduced time and expense 

associated with eliminated inspection station visits. The reduction in station inspections also 

yielded net savings in greenhouse gases and over 195,000 gallons of gasoline. 

Collection Activity 

In 2013, eighteen RSD vans were deployed in the DMA with an additional 4 in the Northern 

Front Range (NFR). Twenty-four different RSD systems were used as some units were 

rotated for preventive or corrective maintenance and four RSD 5000s were used. Van’s 

deployed at 63 locations in the DMA, 28 sites in the NFR and 2 sites in Colorado Springs for 

a total of 23,038 active collection hours. A total 7.1 million emission measurements were 

collected and successfully matched to Colorado registered vehicles. Additional remote 

sensing productivity information is provided in Section IV. 

Expanded vehicle emissions testing began in parts of Weld and Larimer counties in late 2010. 

Vehicle owners with December 2010 renewal dates were the first required to get a test. 

2012 vs 2013 Collection Comparison 

In 2012, RSD performed over 6.7 million emission measurements at 80 locations in the DMA 

and 35 locations in the NFR. In 2013 there were 0.3 million more emission measurements. 

Despite the increase in the quantity of emission measurements the number of clean screens 

issued were 6% lower, being 280,310 in 2012 vs. 263,431 in 2013. 
6 

Vehicle Exemptions 

Almost 274,000 vehicles measured on-road initially met the clean screening exemption 

criteria. Two percent of these were reserved to provide a program audit sample and others 

were eliminated during the QA reviews, for example, as a result of vehicle plate changes. The 

owners of the remaining 263,431 vehicles meeting the clean screening criteria were issued 

notices granting exemption from the I/M test at an inspection station. Of these vehicles, 

233,760 (88.7%) owners took advantage of the Clean Screen exemption. 

Two methods were used to qualify vehicles, 2-RSD and Hybrid. With the 2-RSD method, 

vehicles qualified for an exemption if they had two or more on-road measurements and the 

most recent two measurements both showed emissions within the clean screen standards. 

With the ‘Hybrid’ clean screening method vehicles measured once by remote sensing 

qualified for clean screening if the emissions measurement was within the clean screen 

standards and the vehicle model had a historically low rate of emissions problems. 

A 2% random sample of vehicles that qualified was not issued exemption notices and 4,460 of 

these vehicles were subsequently inspected at an enhanced inspection station. The results of 

the station inspections were used to evaluate the effectiveness of the program. Additional 

information about vehicles mailed notices is provided in Section IV. 

Clean Screen Program Effectiveness 

In a Clean Screen program, some vehicles passing the clean screen emissions criteria might 

have failed if inspected at an inspection station. Therefore, a Clean Screen program, while 

greatly improving convenience for vehicle owners, can slightly reduce the overall 

effectiveness of the I/M program. 

On May 5th 2008, IM240 Denver Metro Area station test standards were tightened – 

especially for HC and NOx – to bring them into closer alignment with EPA final standards. 

The LEI table was updated with subsequent IM240 results to reflect consequent changes in 

inspection result statistics for vehicle models in December 2008, and annually thereafter. The 

RSD standards were updated in October 2010 with the addition of an RSD NO standard of 

1000ppm that first applied to December 2010 registrants. 

Figure I-1 compares the average IM240 exhaust reductions per vehicle inspected at stations to 

those of the 2-RSD audit sample and the Hybrid RSD-LEI audit sample. For HC and CO 

pollutants the RSD-LEI audit sample showed smaller reductions than 2-RSD while the 2-RSD 

method performed better for NOx. 

For 2013, based on the 2% random audit vehicles tested with IM240, it was projected that 

97.3%, 96.7% and 97.6% of HC, CO and NOx of program exhaust emission reductions were 

retained. The impact on gas cap related evaporative emissions was projected to be another 

2.5% of HC reductions. 
7 

Figure I-1 Average IM240 Emissions Reductions 

The methodology for estimating clean screen effectiveness only allows for a score of 100% or 

less and uses the IM240 test as a “gold’ standard. Any variations in vehicle performance or 

the IM240 test procedure that produce an anomalous IM240 test failure are scored against 

Clean Screen. Therefore, it is possible the Clean Screen effectiveness was better than 

projected. 

The recommendations section of the report suggests flexibility be added to Regulation 11 to 

prepare for program changes being implemented in 2015 and their effects on the remote 

sensing program. 

0.00

0.02

0.04

0.06

0.08

Station

2-RSD

RSD-LEI

g/mi

HC

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Station

2-RSD

RSD-LEI

CO

0.00

0.02

0.04

0.06

0.08

0.10

Station

2-RSD

RSD-LEI

NOx
8 

II. Description of the Denver Clean Screening Program 

A. I/M Program Overview 

The Colorado Department of Public Health & Environment (CDPHE) operates an enhanced 

Inspection and Maintenance (I/M) program in the Denver metropolitan area (DMA) and the 

Northern Front Range (NFR). The clean screening component of the IM program uses remote 

sensing equipment to measure the tailpipe emissions of vehicles as they drive by the 

measuring equipment. Vehicles that are determined to have low tailpipe emissions are granted 

an exemption from their I/M inspection. 

Operating rules for the Clean Screening program are contained in the Air Quality Control 

Commission’s Regulation 112

. The Regulation defines the maximum percentages of vehicles 

that may be evaluated by the clean screen program in the enhanced I/M area. In 2006, the 

percentage of vehicles allowed to be evaluated using remote sensing was decreased from 80% 

to 50% as part of an Early Action Compact (EAC) to achieve an earlier attainment 

designation for ozone. 

Clean Screening regulations were expanded in 2007 to allow use of a single RSD 

measurement combined with an index of low emitting vehicles to evaluate exemption 

candidates. The Low Emitter Index (LEI) was developed using I/M240 data to identify 

vehicle groups that historically have a very low probability of failing. The current 

requirement for a vehicle group to qualify as a low emitter is they must have an I/M240 pass 

rate of 98% or greater. 

There are multiple requirements and restrictions for vehicles to participate in the Clean Screen 

program as defined in Regulation 11. The following are the primary elements for vehicles to 

qualify for a clean screen exemption. 

 The applicable observations were within twelve months prior to the individual 

vehicles registration renewal date, 

 The two most recent observation results are below, 200ppm, 0.5%, and 

1000ppm for HC, CO, and NOx respectively, (NOx standard implemented 

October 2010) 

 The two most recent observations must have occurred on a different day or on 

the same day at different site locations, 

Contractor

Envirotest was contracted to operate the enhanced program by a competitive bid process and 

the contract was subsequently amended to include clean screening in the Denver area. 

Envirotest uses technology derived from that originally developed at Denver University with 

whom Envirotest has a royalty agreement. 

Theory of operation 

The RSD is a system designed for a non-intrusive measurement of vehicle emissions. It 

generates and monitors a non-dispersive infrared and dispersive ultra-violet beam emitted and 
9 

reflected approximately 10 to 18 inches above ground preferably across a single lane road. 

Gasoline, diesel, or other fossil fuel powered vehicles drive through this beam and the exhaust 

interferes with this transmission of the beam. Quantifying the interference enables the 

calculation of tailpipe concentrations of CO, HC, CO2, NO and particulate matter. A camera 

simultaneously captures a digitized video image of the rear of the vehicle and its license plate. 

Equipment 

The equipment initially deployed in the Northern Front Range counties were RSD-3000 

mobile units also called AccuScanTM. Successor RSD 4000 units were introduced in 2003. 

Both systems were based on a technical platform developed at the University of Denver by 

Dr. Donald Stedman. In 2007, additional RSD4600 units were added. The RSD4600 is very 

similar to the RSD4000-L3 system described below. The RSD4600 has a more compact 

speed and acceleration measurement bar and more diagnostic ports. Functionally, the two 

systems are the same. One RSD 5000, the latest generation of RSD systems, passed 

acceptance testing in 2011 and began data collection in December 2011. The RSD 5000 is 

more compact, requires less power and supports remote wireless operation. 

AccuScan measures the exhaust of a passing motor vehicle in less than 0.7 seconds. Nondispersive infrared (IR) spectroscopy, the same analytical technique used in garage based twospeed idle and ASM equipment is used to measure concentrations of CO, HC, and CO2. 

Dispersive ultraviolet (UV) spectroscopy is used to measure NOx. The system is based on the 

original designs and patents of Dr. Donald Stedman, professor emeritus at the University of 

Denver. 

The following elements comprise a complete RSD4600 unit: 

 RSD 4-gas analyzer Source Detector Module 

 Corner Cubed Mirror Module (CCM) 

 Two Alignment stands, one each for SDM and CCM 

 Speed/Acceleration subsystem consisting of: 

 Two Speed/Acceleration bars: one emitter and one detector bar with 

adjunct hardware 

 Speed/Acceleration computer 

 Digital Video camera and speed subsystem 

 Computer control console subsystem consisting of: 

 Video monitor 

 PentiumTM–based PC 

 Additional PC cards and internal hardware PC cards: 

 Hard drive 

 Removable Mass Storage 

 Matrox video 

 Serial and COM port 

 RSD operation (data collection) software 

 RSD compatible license plate tag-editing software 
10 

 Calibration and auditing subsystem consisting of: 

 Calibration gas cell 

 Audit tube 

 Audit gas bottle 

 Pressure regulator 

 Hoses with quick disconnects 

 RSD shipping container for SDM and CCM 

The following elements comprise an AccuScanTM van: 

 Ford one-ton truck 

 Triton V-8 engine with 4-speed automatic transmission 

 12 – 14 foot box on bed of truck 

 Roof-mounted 13,500 BTU Coleman air-conditioner 

 5 kW Onan generator 

 Connector panel for quick connection of external cables and calibration 

gas hoses 

The RSD unit takes multiple rapid readings for each vehicle to characterize the exhaust plume 

profile and evaluate whether a valid measurement of a vehicle’s exhaust has been achieved. 

The criteria include how much vehicle exhaust plume is available for the duration of the 

sampling period, evaluation of whether plume measurements are consistent with normal 

plume dissipation, and correction for changes in background concentrations of emissions. 

The RSD units comply with the CDPHE, “Colorado On-road Vehicle Emissions Remote 

Sensing System (COVERS) Specifications” Amended July 20103

: The COVERS accuracy 

specifications are consistent with the California BAR OREMS Specification:1

 and include: 

Detector accuracy: 

1. The CO2% reading shall be within  10% of the Certified Gas Sample, or an absolute 

value of  0.25, or shall be within published manufacturer’s specification – whichever 

is less restrictive. Negative values shall be included and shall not be rounded to zero. 

2. The CO% reading shall be within  15% of the Certified Gas Sample, or an absolute 

value of  0.25 (whichever is greater). Negative values shall be included and shall not 

be rounded to zero. 

3. The HC reading (ppm propane) shall be within  15% of the Certified Gas Sample, or 

an absolute value of  250ppm (whichever is greater). Negative values shall be 

 

1

 On Road Emissions Measurement System OREMS) Specifications, Revision L, Bureau of Automotive Repair, Engineering 

and Technical Research Branch, 10240 Systems Parkway, Sacramento, CA 95827; 2001 California DCA/BAR; p. 5. 
11 

included and shall not be rounded to zero. 

4. The NOx reading (ppm) shall be within  15% of the Certified Gas Sample, or an 

absolute value of  250 ppm (whichever is greater). Negative values shall be included 

and shall not be rounded to zero. 

5. COVERS shall submit readings within the following limits: 

CO + CO2  21.0 %, HC  35,000 ppm hexane, CO2  16.0 %, and NO  7000 ppm. 

6. The system shall record at least three and display at least two measures of plume 

characteristics, for example the maximum number of CO2 molecules seen, the average 

number of CO2 molecules seen, and the number of valid samples (measurements) 

made. 

7. Each unit shall demonstrate during controlled acceptance testing the above criteria 

98% of the time. Ninety-eight percent (98%) shall mean that one hundred percent 

(100%) of the valid records shall have the following fields filled correctly with 

accurate data, ninety-eight percent (98%) of the time: 

CO2% 

CO % 

HC ppm hexane 

NO ppm 

Speed and Acceleration Accuracy: 

1. The vehicle speed measurement should be accurately recorded within  1.0 mile 

per hour. 

2. The vehicle acceleration measurement should be accurately recorded within  0.5 

mile per hour / second. 

3. The speed and acceleration system shall demonstrate during controlled acceptance 

testing the above criteria ninety-five percent 95% of the time. Ninety-five percent 

(95%) shall mean that one hundred percent (100%) of the valid records shall have 

the speed and acceleration fields filled correctly with accurate data, ninety-five 

percent (95%) of the time. 

4. VSP shall be calculated during host processing using the most recent CDPHE 

approved equation. 

Vehicle Identification 

The system captures emissions readings and rear pictures of vehicles passing through the RSD 

infrared beam. The video and emissions readings taken are stored directly on a removable 

media disk and can be used for future reference. 
12 

Envirotest’s TagEditTM software is used to transcribe vehicle license plate information. 

Figure II-1 below shows an example of a TagEditTM screen. This license plate editing service 

is superior to an automatic license plate reader because: 

 All video images associated with valid emissions data get processed. This ensures the 

highest possible vehicle capture rate. 

 Vehicles with special plates are also processed. This is especially important in areas 

where many unique license plates are issued. Failure to process all plate types can create 

a statistically skewed database that could be misinterpreted by the public as “targeting” 

only certain vehicle classes. 

A special registration database was created for the Clean Screen program to allow vehicles to 

be identified (VINs) from Clean Screen license photos captured days prior to their data 

processing. This Clean Screen registration database is updated nightly with all the changes 

statewide that affect what VIN is associated with what plate. A lag time interval is 

incorporated to allow time for updates to get from the County Clerks Offices to the DOR 

database. The separate Clean Screen Registration Database on the Envirotest host contains all 

vehicle registration records statewide, even though only certain counties are expected to 

participate in the Clean Screen program. The future growth of registration could require some 

housekeeping, but there is plenty of hardware scalability to handle this growth. 

Figure II-1: TagEditTM Screen 
13 

B. Measurement Sites 

Good remote sensing sites are critical for obtaining RSD measurements that are representative 

of vehicle operation. Recommended site attributes include: 

(1) Absence of cold start vehicle operating conditions 

(2) Sites where vehicles will generally be accelerating or driving at a steady speed 

uphill to ensure adequate engine power and exhaust plumes and avoid the problem of 

RSD not measuring vehicles that have virtually no exhaust under deceleration 

(3) Absence of enrichment due to high load conditions 

(4) Single lane operation 

(5) High volume traffic 

(6) Unobtrusive siting of the remote sensing equipment 

(7) Adequate median space for safe operation of the RSD equipment. 

Table II-1 lists the RSD sites in the Northern Front Range (NFR), the number of days each 

site was used, the total hours during which measurements were collected and the number of 

vehicles measured per hour. The hours shown do not include travel time to and from the site, 

equipment set-up and equipment takedown time. 

Table II-2 lists the Denver Metro Area (DMA) site locations. 

Table II-3 lists the El Paso County (Colorado Springs) locations where a small number of 

measurements are made annually. 

Site locations in the NFR and DMA are illustrated in Figures II-2a and IIb. Blue sites are 

active. Red sites are no longer permitted. The X's represent HQ and other stations where RSD 

vans are housed. 
14 

Table II-1 Northern Front Range 

Site 

Code Location City

Active 

Days

Total 

Active 

Hours

Registered 

Vehicles 

Measured

Veh's 

Per 

Hour

2144 NB STANDFORD FROM MONROE DR FT COLLINS 2 10 802 78

3019 ON RAMP TO NB I-25 FROM 402 (CR-54) LOVELAND 16 68 6,703 99

3020 ON RAMP TO SB I-25 FROM 402 (CR-54) LOVELAND 20 109 12,974 119

3510 SB SHIELDS ST. AFTER FOSSIL CREEK FT. COLLINS 3 18 3,613 200

3511 OFF-RAMP FROM NB I-25 TO WB MULBERRY ST. FT. COLLINS 28 209 59,474 285

3513 NB SHIELDS RD. AFTER BON HOMME RD. FT. COLLINS 4 23 1,122 50

3514 NB TAFT HILL RD. AFTER HARMONY RD. FT. COLLINS 77 521 196,148 377

3515 ONRAMP TO NB I-25 FROM WB US-34 FT. COLLINS 32 236 34,364 146

3517 ONRAMP TO SB I-25 FROM CROSSROADS BLVD. FT. COLLINS 4 29 2,963 102

3527 EB 392 AFTER INTERSECTION WITH CR-9 FT. COLLINS 19 149 23,993 161

8042 ONRAMP TO SB I-25 FROM EAST PROSPECT FT COLLINS 71 521 123,542 237

8049 ONRAMP TO SB I-25 FROM HARMONY RD FT COLLINS 23 160 42,080 264

8053 EB US-287 ABOUT 500' EAST OF LCR-17 BERTHOUD 14 80 3,205 40

2989 EB US 34 BYPASS FROM 23RD AVE GREELEY 43 314 46,298 147

3506 ONRAMP TO NB US-85 FROM HWY 52 FT. LUPTON 2 12 558 48

3507 ONRAMP TO SB US-85 FROM HWY 52 FT. LUPTON 10 58 8,730 151

3518 ONRAMP TO SB I-25 FROM SR-60 LOVELAND 4 27 2,180 81

3519 ONRAMP TO SB I-25 FROM SR-56 BERTHOUD 5 21 866 41

3520 ONRAMP TO SB I-25 FROM SR-66 LONGMONT 1 5 542 118

3521 ONRAMP TO SB I-25 FROM SR-52 LONGMONT 44 256 63,414 247

3522 ONRAMP TO SB I-25 FROM CR-8 DACONO 10 49 3,692 75

3523 ONRAMP TO NB I-25 FROM CR-8 DACONO 1 4 31 7

3524 ONRAMP TO NB I-25 FROM SR-52 LONGMONT 2 9 845 94

3525 ONRAMP TO NB I-25 FROM SR-119 LONGMONT 11 49 6,455 133

3526 ONRAMP TO NB I-25 FROM SR-66 LONGMONT 5 28 2,291 81

8043 ONRAMP TO WB US-34 FROM 27TH ST GREELEY 44 325 68,123 210

8044 ONRAMP TO EB US-34 FROM SH-257 GREELEY 36 262 29,980 115

8045 ONRAMP TO EB US-34 BYPASS FROM SH-257 GREELEY 38 289 35,233 122

Subtotal 569 3,839 780,221 203
15 

Table II-2 Denver RSD Sites 

Site 

Code Location City

Active 

Days

Total 

Active 

Hours

Registered 

Vehicles 

Measured

Veh's 

Per 

Hour

2819 ONRAMP TO SB 121 FROM WB 287 WESTMINSTER 87 815 206,075 253

2821 ONRAMP TO NB I-25 FROM 120TH AVE WESTMINSTER 9 84 14,759 177

2971 EB DILLON RD EAST OF US-287 BROOMFIELD 54 381 118,851 312

8072 ONRAMP TO NB I-25 FROM 84TH AVE. THORNTON 5 61 11,552 189

8073 ONRAMP TO NB I-25 FROM 104TH AVE. NORTHGLENN 13 96 13,906 144

8087 ONRAMP TO WB I-70 FROM AIRPORT BLVD. AURORA 20 160 31,262 195

8088 ONRAMP TO WB I-76 FROM 88TH AVE COMMERCE CITY 12 97 12,445 128

8089 ONRAMP TO WB I-76 FROM 96TH AVE COMMERCE CITY 12 101 23,263 230

8090 ONRAMP TO EB I-76 FROM PECOS ST. DENVER 1 4 222 51

8091 ONRAMP TO WB I-76 FROM BROMLEY LN. BRIGHTON 6 35 4,163 119

8093 ONRAMP TO WB I-70 FROM NB I-25 DENVER 219 2,196 1,196,269 545

8103 ONRAMP TO WB I-270 FROM SB SH-2 COMMERCE CITY 2 13 721 56

8107 ONRAMP TO WB US-36 FROM BROADWAY DENVER 102 856 256,592 300

8115 ONRAMP TO EB I-76 FROM FEDERAL BLVD DENVER 7 64 7,536 118

8129 ONRAMP TO WB I-76 FROM PECOS ST DENVER 35 275 42,281 154

8098 ONRAMP TO NB I-225 FROM ILLIFF AVE AURORA 22 152 26,200 173

8120 ONRAMP TO SB I-225 FROM ALAMEDA AVE AURORA 24 191 27,896 146

2512 ONRAMP TO NB SH-157 FROM PEARL ST. BOULDER 8 51 7,350 145

2514 ONRAMP TO 96TH AVE FROM SH-42. BOULDER 41 269 54,507 202

2826 ONRAMP TO EB US-36 FROM MCCASLIN LOUISVILLE 35 227 29,450 130

8057 ON-RAMP TO SB SH 157 FROM PEARL ST. BOULDER 68 445 93,314 210

8064 ONRAMP TO NB SH 157 (FOOTHILLS PKAY) FROM EB TABLE MESA BOULDER 2 12 2,040 171

2166 ONRAMP TO WB I-76 FROM WB I-270 DENVER 3 22 1,272 59

2171 ONRAMP TO WB I-70 FROM PECOS ST. DENVER 1 1 177 185

2456 ONRAMP TO SB I-225 FROM PEORIA ST DENVER 21 155 30,739 198

2560 ONRAMP TO EB US-6TH AVE FROM SB I-25 DENVER 8 84 14,773 175

3499 ONRAMP TO SB I-25 FROM WB I-76 DENVER 4 22 7,431 340

3504 ONRAMP TO EB I-70 FROM PEORIA ST. DENVER 23 161 49,530 308

3505 ONRAMP TO WB I-70 FROM QUEBEC ST. DENVER 59 441 175,540 398

8062 ONRAMP TO EB I-70 FROM FEDERAL BLVD DENVER 4 48 8,481 177

8081 ONRAMP TO EB I-70 FROM HAVANA ST. DENVER 20 158 33,522 212

8094 ONRAMP TO SB US-285 (HAMPDEN AVE) FROM FEDERAL BLVD SHERIDAN 83 627 155,689 248

8097 ONRAMP TO WB US-6TH AVE FROM NB I-25 DENVER 171 1,222 864,160 707

8113 ONRAMP TO SB US-285 (HAMPDEN AVE) FROM SHERIDAN BLVD. DENVER 22 175 36,436 208

8122 ONRAMP TO NB I-25 FROM PARK AVE DENVER 126 1,173 391,149 334

8123 ONRAMP TO NB I-25 FROM 58TH AVE. DENVER 91 878 239,905 273

2319 ONRAMP TO EB C-470 FROM LUCENT BLVD HIGHLANDS RANCH 27 188 45,511 242

2320 ONRAMP TO EB C-470 FROM BROADWAY HIGHLANDS RANCH 7 51 23,147 455

2321 ONRAMP TO EB C-470 FROM UNIVERSITY BLVD HIGHLANDS RANCH 67 478 147,106 308

2322 ONRAMP TO WB C-470 FROM UNIVERSITY BLVD HIGHLANDS RANCH 38 295 75,304 255

2576 ONRAMP TO SB I-25 FROM EB COUNTY LINE RD. HIGHLANDS RANCH 33 230 52,309 227

2577 ONRAMP TO NB I-25 FROM EB COUNTY LINE RD. HIGHLANDS RANCH 105 754 314,992 418

8077 ONRAMP TO EB C-470 FROM QUEBEC ST. HIGHLANDS RANCH 95 652 340,218 522

8083 ONRAMP TO SB I-25 FROM FOUNDERS PARKWAY (EXIT 184) CASTLE ROCK 44 310 53,427 172

8084 ONRAMP TO SB I-25 FROM LINCOLN AVE. LITTLETON 17 113 14,001 124

8085 ONRAMP TO NB I-25 FROM WOLFENSBERGER RD. (EXIT 182) CASTLE ROCK 42 286 86,777 304

8086 ONRAMP TO NB I-25 FROM FOUNDERS PARKWAY (EXIT 184) CASTLE ROCK 39 261 73,439 281

2175 ONRAMP TO WB C-470 FROM KIPLING ST. LAKEWOOD 1 8 1,845 232

2176 ONRAMP TO WB C-470 FROM KEN CARYL AVE LAKEWOOD 93 620 155,578 251

2400 ONRAMP TO WB C-470 FROM NB US-285 (HAMPDEN AVE) LAKEWOOD 1 4 785 210

2458 ONRAMP TO WB US-6TH AVE FROM SIMMS ST LAKEWOOD 44 362 84,963 234

2461 ONRAMP TO WB US-6TH AVE FROM NB WADSWORTH BLVD LAKEWOOD 12 122 23,617 193
16 

Table II-2 Denver RSD Sites continued 

Table II-3 El Paso RSD Sites 

Site 

Code Location City

Active 

Days

Total 

Active 

Hours

Registered 

Vehicles 

Measured

Veh's 

Per 

Hour

8058 ONRAMP TO WB I-76 FROM SHERIDAN BLVD. ARVADA 44 330 68,067 206

8068 ONRAMP TO EB I-70 FROM HARLAN ST. ARVADA 1 8 1,492 178

8069 ONRAMP TO WB I-70 FROM KIPLING ST. WHEATRIDGE 65 535 131,941 247

8099 ONRAMP TO WB US-6TH AVE FROM SB WADSWORTH BLVD LAKEWOOD 2 9 1,351 146

8100 ONRAMP TO WB US-6TH AVE FROM SB KIPLING ST. LAKEWOOD 17 125 28,281 227

8104 ONRAMP TO SB US-285 (HAMPDEN AVE) FROM WADSWORTH BLVD. DENVER 10 83 7,634 92

8105 ONRAMP TO SB US-285 (HAMPDEN AVE) FROM KIPLING BLVD. DENVER 3 13 2,008 159

8106 ONRAMP TO NB US-285 (HAMPDEN AVE) FROM KIPLING BLVD. DENVER 68 706 156,954 222

8111 ONRAMP TO EB SH-58 FROM MCINTYRE ST. GOLDEN 65 597 162,453 272

8130 ONRAMP TO EB I-76 FROM SHERIDAN BLVD ARVADA 19 153 33,771 221

8131 ONRAMP TO EB I-70 FROM SHERIDAN BLVD. ARVADA 7 46 5,114 111

Subtotal 2,386 19,090 6,281,543 329

Site 

Code Location City

Active 

Days

Total 

Active 

Hours

Registered 

Vehicles 

Measured

Veh's 

Per 

Hour

2518 ONRAMP TO E.PLATTE AVE FROM NB ACADEMY BLVD COLORADO SPRINGS 8 53 7,876 148 

2520 ONRAMP TO NB I-25 FROM N.ACADEMY BLVD COLORADO SPRINGS 10 56 8,604 153 

Subtotal 18 109 16,480 151

Total 2,973 23,038 7,078,244 307
17 

Figure II-2 a: Site Locations Northern Front Range 
18 

Figure II-2 b: Site Locations – Denver Metro Area 

C. Sources of Data and Description of Elements 

Data used in the analyses in this report come from three primary sources: 

 Remote sensing unit measurements 

 The DMV database maintained on the AIR program contractor host computer 
19 

 I/M test database maintained on the AIR program contractor host computer 

Data from the RSD units are loaded into a database maintained by the centralized 

contractor, Envirotest. Using the vehicle plate identified by RSD, the registration file is 

accessed to determine the vehicle identification number (VIN) and vehicle registration 

information. Envirotest uses the Polk VIN Decoder to add additional information about 

each vehicle. The combined data fields are shown in Table II-4. 

Table II-4 Vehicle Measurement Information 

Field Name Description 

V_DATA_VER Data version 

V_DATE_TIME Date and time of measurement 

V_RSD_UNIT RSD system number 

V_SEQ_NUM Measurement sequence number 

V_SITE_CODE Site reference 

V_PROGRAM_CODE I/M Program 

V_VAN_OPERATOR_ID 

V_CO Carbon monoxide emissions % 

V_CO2 Carbon dioxide emissions % 

V_MAX_CO2 Maximum observed CO2 

V_CO2_VOLUME Volume of CO2 observed 

V_HC Hydrocarbon emissions ppm hexane equivalent 

V_NOX Oxides of nitrogen emissions ppm (NOx) 

V_NOX_FLAG Validity of NOx measurement 

V_OPAC Opacity measurement 

V_SPEED Speed MPH 

V_ACCEL Acceleration MPH/S 

V_SA_UNITS Units of speed and acceleration 

V_TEMPERATURE Ambient temperature 

V_HUMIDITY Ambient humidity 

V_WIND_SPEED Ambient wind speed 

V_WIND_DIRECTION Ambient wind direction 

V_WEATHER_UNITS 

V_PLATE_CONFIDENCE Reserved for future use 

V_ALPR_VENDOR Reserved for future use 

V_TEST_COUNTY Reserved for future use 

V_CRC 

V_TAG_EDIT_MODE 

V_TAG_EDIT_ID_1 

V_TAG_EDIT_ID_2 

V_TAG_EDIT_ID_3 

V_TAG_EDIT_EMP_1 

V_TAG_EDIT_EMP_2 

V_TAG_EDIT_EMP_3 

V_PLATE License plate 

V_PLATE_STATE State issuing license plate 

V_PLATE_TYPE Type of plate 

V_VIN Vehicle Identification Number 
20 

Field Name Description 

V_LZIP Zip code for legal owner address 

V_STATE_MAKE Make code 

V_STATE_MODEL Model code 

V_COUNTY County of registration 

V_VEH_YEAR Model year 

V_EM_FLAG Subject to emissions test 

V_POLK_VEH_YEAR Polk decoded model year 

V_POLK_MAKE Polk decoded make 

V_POLK_VEH_TYPE Polk decoded vehicle type (P-pass, T-truck, U-unknown) 

V_POLK_MODEL Polk decoded model 

V_POLK_DISP Polk decoded engine displacement 

V_VSP Calculated vehicle specific power during measurement 
21 

III. Summary of Data Collection 

Up to 22 remote sensing units were deployed for 2,973 days during 2013 to collect 7.1M 

measurements having a visible plate and valid HC, CO, speed and acceleration values: 6.3M 

measurements in the Denver metropolitan area (DMA) Metro Area, 780,000 measurements in 

the Northern Front Range (NFR) and 16,000 measurements in El Paso County. 

Clean screen exemption notices were issued for 263,432 vehicles scheduled to renew their 

registration in 2013 and due for emissions testing (Table III-1) comprising 221,334 DMA 

vehicles and 42,097 NFR vehicles. 

Vehicles registered in the DMA accounted for over 5.6M measurements, the NFR for 743,000, 

and El Paso County 108,000. Another 253,000 measurements were of vehicles registered in 

other Colorado counties (Table III-2). 

In 2012, RSD performed 6.7 million emission measurements and 280,310 clean screens were 

issued. 

Table III-1 Collection Summary 

A. Monthly Collection Activity 

Figure III-1 shows the monthly RSD measurements. Collection rates were lower during severe 

winter months. 

B. Measurements by Hour of Day 

Figure III-2 ‘Measurements by Hour of Day’ shows the number of vehicles measured during 

each hour of the day. The shape of the curve is indicative of when measurements were collected 

and does not represent the level of traffic during the day. Most measurements were collected 

between 7:00am and 7:00pm. 

Statistic

Denver Metro 

Area

Northern 

Front Range

Colorado 

Springs Total

Sites Used 63 28 2 93 

Collection Van Days 2,386 569 18 2,973 

Active Collection Van Hours 19,090 3,839 109 23,038 

Matched to Registration 6,281,543 780,221 16,480 7,078,244 

Notices Generated for 2013 renewals 221,334 42,097 263,431
22 

Figure III-1 Monthly RSD Measurements 

Figure III-2 Measurements by Time of Day 

0

100,000

200,000

300,000

400,000

500,000

600,000

700,000

800,000

900,000

1,000,000

Jan

FebMar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Measurements

Measurements by Month

El Paso

County

Northern

Front Range

Denver Metro

Area

0

100,000

200,000

300,000

400,000

500,000

600,000

700,000

800,000

900,000

Before 6 am

6-7 am7-8 am8-9 am

9-10 am

10-11 am11-12 am

12 -1 pm

1-2 pm2-3 pm3-4 pm4-5 pm5-7 pm6-7 pm7-8 pm

Measurements

Measurements by Time of Day

El Paso

County

Northern

Front Range

Denver Metro

Area
23 

C. Composition of Vehicles Measured 

Table III-2, Source of Vehicle Registrations Measured by RSD, shows the number of vehicles 

registered in each program area and the area where they were measured. The majority (98%) of 

Denver Metropolitan Area registered vehicles were measured within the DMA. A majority 

(79%) of Northern Front Range registered vehicles were measured in NFR with the remaining 

21% being measured in the DMA. 

Table III-3, Type of Vehicles Measured by RSD within Registration Jurisdiction, shows that 

79.8% of vehicles measured were registered in the DMA, 10.5% in the NFR, 1.5% in El Paso 

County (Colorado Springs), 3.6% in other non-I/M counties, and 4.6% were not matched. This 

can occur when plates are transferred by an owner to a new vehicle. These numbers are 

indicative of on-road activity – not unique registrations. The same vehicle may be measured 

more than once. 

Table III-4 shows the distribution of vehicle measurements by vehicle type, age group and 

registration jurisdiction. The vehicle types were identified by the Polk VIN decoder. The model 

years of 1980 and older vehicles and some of the newest models were determined from the 

registration information but the vehicle type was not available. These were classified as 

Unknown in Table III-3. One thousand and fifty-one measurements of motorcycles were also 

recorded. 

Table III-2 Source of Vehicle Registrations Measured by RSD 

Measured In

Denver Metro Area Northern Front Range El Paso

Adams 864,222 97% 25,472 3% 171 0% 889,865 

Arapahoe 735,400 97% 18,545 2% 443 0% 754,388 

Boulder 254,639 91% 25,191 9% 54 0% 279,884 

Broomfield 145,837 97% 3,772 3% 17 0% 149,626 

Denver 1,001,642 98% 20,474 2% 453 0% 1,022,569 

Douglas 792,648 99% 8,379 1% 406 0% 801,433 

Jefferson 1,694,294 99% 16,974 1% 216 0% 1,711,484 

State of Colorado 34,896 87% 4,925 12% 326 1% 40,147 

Subtotal Denver Metro 5,523,578 98% 123,732 2% 2,086 0% 5,649,396 

Larimer 52,049 13% 349,857 87% 63 0% 401,969 

Weld 102,899 30% 238,738 70% 52 0% 341,689 

Subtotal Northern Front Range 154,948 21% 588,595 79% 115 0% 743,658 

El Paso El Paso 88,199 81% 7,484 7% 12,813 12% 108,496 

Non I/M 228,114 90% 24,015 9% 785 0% 252,914 

Not Matched 323,780

Total 5,994,839 743,826 15,799 7,078,244 

Registered 

County

Total

Northern Front 

Range

Denver Metro Area

Program
24 

Table III-3 Type of Vehicles Measured by RSD within Registration Jurisdiction 

Table III-4 Registered Jurisdiction and Age of Vehicles Measured by RSD 

Program County Pass Truck Unknown Total %

Adams 342,518 543,312 4,035 889,865 12.6%

Arapahoe 298,728 452,936 2,724 754,388 10.7%

Boulder 123,825 154,957 1,102 279,884 4.0%

Broomfield 63,807 85,382 437 149,626 2.1%

Denver 423,627 593,954 4,988 1,022,569 14.4%

Douglas 275,290 524,629 1,514 801,433 11.3%

Jefferson 664,064 1,041,676 5,744 1,711,484 24.2%

State of Colorado 10,134 27,952 2,061 40,147 0.6%

Denver Metro 2,201,993 3,424,798 22,605 5,649,396 79.8%

Larimer 159,649 240,134 2,186 401,969 5.7%

Weld 132,518 207,381 1,790 341,689 4.8%

Subtotal North Front Range 292,167 447,515 3,976 743,658 10.5%

El Paso El Paso 44,634 63,022 840 108,496 1.5%

Non I/M 87,634 162,314 2,966 252,914 3.6%

Not Matched 4.6% 323,780

Total 2,626,428 4,097,649 30,387 7,078,244 100.0%

Denver Metro

Northern Front 

Range

 Vehicle 

Type Model Year 

 Denver 

Metro Area 

 Northern 

Front Range El Paso 

 NonI/M Total 

Pass 1981 & older 279 46 18 45 388 

1982-1990 31,028 5,224 761 2,056 39,069 

1991-1995 114,582 17,789 2,456 5,872 140,699 

1996-2000 374,788 52,498 7,442 15,992 450,720 

2001-2005 651,081 90,678 13,540 27,185 782,484 

2006-2010 656,463 84,211 13,163 24,525 778,362 

2011 & newer 373,772 41,721 7,254 11,959 434,706 

 Light 

Truck 1981 & older 409 86 13 126 634 

1982-1990 27,146 5,053 646 2,766 35,611 

1991-1995 108,010 16,889 2,425 7,381 134,705 

1996-2000 480,961 64,364 8,781 25,025 579,131 

2001-2005 1,051,982 138,572 19,945 49,776 1,260,275 

2006-2010 1,107,505 141,135 20,405 50,151 1,319,196 

2011 & newer 648,785 81,416 10,807 27,089 768,097 

Unknown 1981 & older 10,619 1,920 354 1,358 14,251 

1982-1990 364 91 43 135 633 

1991-1995 562 111 32 113 818 

1996-2000 1,516 328 52 300 2,196 

2001-2005 2,806 514 102 313 3,735 

2006-2010 2,841 530 109 355 3,835 

2011 & newer 2,872 346 57 181 3,456 

Motorcycles 613 136 91 211 1,051 

Total 743,658 5,648,984 108,496 252,914 6,754,052 
25 

IV. Clean Screening Program Performance 

A. Vehicles Selected, Notices and Redemptions 

In 2013, there were 273,824 vehicles qualifying for participation in the clean screen program. 

Table IV-1 summarizes the monthly number of vehicles meeting screening criteria each month, 

including the number withheld for the random sample and the number rejected through QA 

checks. 

 

A random sample of two percent of vehicles meeting Clean Screen criteria are not mailed 

notices. These vehicles are required to go to a test station to obtain the station-based emission 

inspection. This random sample of vehicles is used to evaluate the effectiveness of the Clean 

Screen program. 

Not all vehicles notified for clean screen or withheld in the random sample redeem the clean 

screen or obtain a test at that time, for example vehicles changing owner were likely to have 

obtained an earlier station inspection. Compared to the 263,431 vehicles notified in the year, 

fewer vehicles 233,760 (88.7%) obtained a clean screen. 

Table IV-1 Vehicles Qualified As Meeting Clean Screening Criteria by Status 

 Table IV-2 lists the number of vehicles by month and city notified via the Department of 

Revenue. Table IV-3 shows inspection results of the audit sample. Just 0.6% of the audit 

sample failed their exhaust emissions inspection down from 0.9% in 2012. Gas cap pressure test 

failures of 3.4% were up from 3.3% in 2012. 

Reg 

Year

Reg 

Month

Random 

Sample QA failed Notified

Total 

Qualified

Random 

% of 

Qualified

2013 Jan 482 787 22,880 24,149 2.0%

2013 Feb 462 463 22,235 23,160 2.0%

2013 Mar 486 272 23,425 24,183 2.0%

2013 Apr 432 242 20,840 21,514 2.0%

2013 May 450 324 21,660 22,434 2.0%

2013 Jun 463 274 22,577 23,314 2.0%

2013 Jul 494 293 23,362 24,149 2.0%

2013 Aug 497 361 23,961 24,819 2.0%

2013 Sep 484 615 22,332 23,431 2.1%

2013 Oct 496 559 23,770 24,825 2.0%

2013 Nov 393 414 18,539 19,346 2.0%

2013 Dec 363 287 17,850 18,500 2.0%

Total 5,502 4,891 263,431 273,824 2.0%
26 

Table IV-2 Notifications Transmitted to DOR 

Table IV-3 Clean Screen Audit Test Pass / Fail Statistics 

Registration Renewal Month

City Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total

DENVER 3,743 3,539 4,033 3,559 3,808 4,125 4,291 4,112 3,888 4,067 3,390 3,339 45,894

AURORA 1,680 1,553 1,656 1,479 1,435 1,442 1,511 1,655 1,431 1,634 1,235 1,197 17,908

LITTLETON 1,262 1,245 1,264 1,175 1,140 1,335 1,390 1,447 1,257 1,454 1,102 1,102 15,173

FT COLLINS 1,247 1,153 1,259 1,126 1,191 1,222 1,201 1,311 1,195 1,342 1,027 895 14,169

ARVADA 1,062 1,112 1,149 1,093 1,132 1,228 1,271 1,348 1,252 1,349 1,011 1,030 14,037

LAKEWOOD 1,097 1,080 1,127 1,040 1,093 1,094 1,122 1,241 1,266 1,293 1,044 988 13,485

HIGHLAND RCH 998 1,092 1,041 908 1,008 971 1,080 1,181 1,106 1,176 842 821 12,224

WESTMINSTER 961 833 910 776 795 905 883 903 855 831 682 715 10,049

THORNTON 893 874 893 782 869 859 820 836 752 859 643 625 9,705

CENTENNIAL 800 769 819 703 697 716 750 805 807 835 728 615 9,044

CASTLE ROCK 676 622 664 560 600 683 716 688 684 673 528 476 7,570

GREELEY 554 610 663 611 593 572 653 619 577 627 457 409 6,945

BROOMFIELD 683 671 664 568 614 591 596 584 540 544 440 428 6,923

BOULDER 777 708 645 598 550 588 577 564 478 516 346 423 6,770

LOVELAND 507 560 609 528 600 579 568 581 575 596 429 376 6,508

GOLDEN 538 495 471 437 473 539 570 573 521 604 493 452 6,166

PARKER 548 498 533 477 480 492 528 559 521 548 406 411 6,001

LONGMONT 427 459 469 376 414 377 402 389 316 371 275 263 4,538

ENGLEWOOD 387 374 375 383 365 351 377 430 371 383 267 316 4,379

WHEAT RIDGE 238 238 266 266 253 230 252 267 293 274 221 237 3,035

BRIGHTON 252 244 271 236 246 224 234 235 236 244 214 192 2,828

NORTHGLENN 277 250 240 253 250 260 255 242 186 263 177 153 2,806

WINDSOR 226 204 238 211 228 231 272 282 275 245 201 157 2,770

COMMERCE CITY 227 230 227 183 196 207 221 251 214 217 175 128 2,476

LAFAYETTE 171 170 177 171 160 189 209 198 183 212 153 143 2,136

LOUISVILLE 166 180 167 145 152 168 186 174 172 183 135 130 1,958

ERIE 178 175 199 165 179 170 174 162 156 157 102 123 1,940

EVERGREEN 141 137 148 126 172 159 179 176 151 165 133 150 1,837

MORRISON 175 148 124 125 131 148 151 137 139 161 103 111 1,653

GREENWOOD VLG 139 130 138 108 150 130 119 156 165 166 108 97 1,606

LONE TREE 153 143 133 116 114 128 103 142 116 145 103 103 1,499

EVANS 104 138 133 106 127 125 117 113 110 104 103 84 1,364

CASTLE PNS N 106 114 114 100 100 138 126 145 100 123 108 86 1,360

JOHNSTOWN 96 89 104 100 96 100 112 110 122 109 93 81 1,212

SUPERIOR 104 121 113 69 90 87 91 105 90 73 86 80 1,109

FREDERICK 80 71 88 66 61 88 94 110 104 107 82 88 1,039

BERTHOUD 90 79 92 79 77 72 71 69 75 65 55 56 880

FIRESTONE 70 100 83 57 61 77 73 66 71 95 63 45 861

CONIFER 78 99 82 61 76 69 63 57 63 65 54 42 809

OTHER 969 928 1,044 918 884 908 954 938 919 895 725 683 10,765

Total 22,880 22,235 23,425 20,840 21,660 22,577 23,362 23,961 22,332 23,770 18,539 17,850 263,431

Vehicle Type Vehicles

Fail 

Emissions

Fail Gas 

Cap / 

Pressure

Fail 

Inspection

Passenger 1,827 9 68 75 

Light Truck 2,633 18 85 102 

Total 4,460 27 153 177 

Percentage 0.6% 3.4% 4.0%
27 

B. Clean Screen Program Effectiveness 

The emissions reductions obtained during the station testing of the audit sample vehicles are used 

to project the total emissions reductions foregone as a result of the Clean Screen program. 

Pass / Fail Statistics 

Matching initial tests for audit vehicles were limited to those occurring after the second RSD 

measurement and before expiration of the assigned Clean Screen period. Matching reinspections following an initial failure were sought through the end of February 2014. The 

inspections identified for audit sample vehicles and the inspection results are tabulated in Table 

IV-3. As noted earlier, some of the anticipated random vehicles did not obtain a test within the 

Clean Screen period. In aggregate, 0.6% of the tested audit vehicles failed their tailpipe 

emissions inspection, and 3.4% of the tested audit vehicles failed their gas cap pressure test2

. 

Following sections describe in detail how these results are used to evaluate the emissions impact 

of the Clean Screen program. 

Tailpipe Emissions 

Over 93% of inspected vehicles, and 95% of the clean screen audit vehicles, were tested using 

IM240. Models inspected using the idle test included 1981-and-older models and 1982-andnewer trucks over 8500 lbs GWWR plus some four-wheel drive and traction control vehicles. 

Few of these were clean screened. The IM240 test provides a more accurate estimate of in-use 

vehicle exhaust emissions than the idle tailpipe test. Therefore, the results of the clean screen 

audit sample vehicles tested using IM240 were used to evaluate the exhaust emissions 

effectiveness of the clean screen program. 

Vehicle test results were sorted by VIN and test date. Vehicles were then further classified based 

on their first and last test result during the period. To avoid potential double counting of 

emissions reductions, the emissions analysis only considered the first and last result for each 

vehicle during the year and interim results were ignored. 

In the list below, the first and last results are indicated in parenthesis, where P is pass, F is fail, 

W is waiver and null indicates there was only a single test result for a particular vehicle. The 

expected combinations applying to the vast majority of vehicles are underlined. 

 P – Passed initial test (P/null, P/P, P/F, P/W) 

 R – Failed and successfully repaired (F/P) 

 U – Failed unresolved (F/null, F/F) 

 W – Failed and wavered (F/W) 

 

2

 Note that the number of emissions fails plus the number of Gas Cap / Gas Cap Pressure failures does not always equal the total

number of inspection failures. In a few cases a vehicle may fail both Emissions and Gas Cap. In a few cases, vehicles fail for 

other reasons. 
28 

The difference between the initial and final tests is used to determine the percentage of tailpipe 

emissions reduction of each group. For vehicles with only one test, the final result is the same as 

the initial result. 

Adjustment of Fast-Pass Results 

A majority of vehicles tested on IM240 fast pass the test in less than the 240-second driving 

cycle. To allow for comparison of emissions of vehicles tested over different durations of the 

IM240 test cycle, the emission results for vehicles fast-passing the IM240 inspection must be 

extrapolated. A method for projecting full test emissions was developed and implemented in the 

I/M program in 19964 and the projected full test emissions values are stored in the test records 

and reported as the emissions results. 

Unresolved Vehicles 

When vehicles fail their initial inspection, they must obtain a repair and return for re-inspection. 

This process is normally completed in 30 days, but can take longer. Vehicles having initial tests 

in late 2013 but completing repair and final test after February of the following year are treated 

as unresolved. Thus, the “Fail unresolved” category may be somewhat over-stated. 

A number of vehicles never complete the repair/re-inspection process. In most cases, these 

vehicles are either scrapped or removed from the non-attainment area, which does reduce 

emissions in the area. Surveys in Arizona5

 and Colorado6 found that some vehicles continued to 

operate in the area in violation of the program rules, either with expired license plates or with 

stolen license plates or license plate stickers. In this report, it is assumed that two-thirds of these 

unresolved vehicles leave the area and one third continues to operate. Recent studies in 

Colorado indicate the percentage leaving the area may be as high as 80%. 

To minimize the number of unresolved Clean Screen audit vehicles, retests of audit vehicles 

were included through the end of February 2014 and the audit vehicles were all assumed to 

remain in the area. 

First and Final Emissions Results 

Table IV-4 contains an example of the initial and final tailpipe results for 1982 to 1985 passenger 

vehicles inspected using the IM240 test. The table shows the average initial and average final 

emissions for each group of vehicles together with the percentage reduction. 

For example, of the 1,428 1985 model year passenger vehicles tested using the IM240 transient 

test, 15.8% of vehicles initially failed inspection and were repaired (Pass) with HC, CO and NOx 

reductions of 50.7%, 68.7% and 8.8%. Another 7.4% of vehicles failed their initial inspection 

and had not successfully passed a retest by end February 2014 (Unresolved). Reductions from 

these vehicles are estimated to be approximately 66% for HC, CO and NOx, because follow-up 

studies have shown that more than two thirds cease operating in the area. Finally, 0.1% of 

vehicles were waived (Waiver) with CO reductions of 35.6% and increases in HC and NOx. In 

aggregate, including vehicles passing their initial inspection, emission reductions for 1985 

passenger vehicles were 24.9% for HC, 35.6% for CO and 6.2% for NOx. 

Complete tables by model year and vehicle type are provided in Appendix A for vehicles tested 

using the IM240. Tables are also provided for the Clean Screen audit sample vehicles. 
29 

Table IV-4 Transient Test Emission Reductions for 1982-1985 Passenger Vehicles 

Appendix A1 Colorado 2013 Transient Test Emissions Reductions

Unresolved fails remaining in area 33%

Model First Last Initial Final Reduction 

Year/Type Result Result Vehicles Fail% HC CO NOX HC CO NOX HC C

1982 Pass - 258 1.62 19.18 2.02 1.62 19.18 2.02 0.0% 0.0% 

P Fail Pass 59 17.2% 4.56 51.09 2.02 1.52 19.35 1.88 66.6% 62.1% 

Fail Unresolv. 26 7.6% 5.59 85.27 1.92 1.99 29.03 0.65 64.4% 66.0% Fail Waiver 1 0.3% 1.49 70.11 0.38 1.49 70.11 0.38 0.0% 0.0% 

Total Fail% 344 25.0% 2.42 29.80 2.00 1.63 20.10 1.88 32.7% 32.5% 

1983 Pass - 462 1.29 12.26 2.07 1.29 12.26 2.07 0.0% 0.0% 

P Fail Pass 98 16.0% 2.32 36.51 2.06 1.24 14.85 1.79 46.7% 59.3% 

Fail Unresolv. 49 8.0% 4.46 73.11 1.91 1.56 24.31 0.57 65.1% 66.7% Fail Waiver 3 0.5% 4.50 140.30 1.08 4.73 146.55 0.24 -5.0% -4.5% 

Total Fail% 612 24.5% 1.73 21.65 2.05 1.32 14.30 1.89 23.5% 33.9% 

1984 Pass - 619 1.23 11.35 1.92 1.23 11.35 1.92 0.0% 0.0% 

P Fail Pass 147 17.3% 2.86 39.51 1.97 1.44 14.26 2.05 49.7% 63.9% 

Fail Unresolv. 79 9.3% 5.47 75.77 1.82 1.73 23.32 0.59 68.4% 69.2% Fail Waiver 6 0.7% 5.14 112.15 1.64 4.98 116.14 1.55 3.2% -3.6% 

Total Fail% 851 27.3% 1.94 22.90 1.92 1.34 13.70 1.82 30.7% 40.2% 

1985 Pass - 1,094 1.05 10.84 1.89 1.05 10.84 1.89 0.0% 0.0% 

P Fail Pass 226 15.8% 2.21 31.01 2.12 1.09 9.71 1.93 50.7% 68.7% 

Fail Unresolv. 106 7.4% 3.92 58.15 1.79 1.34 19.49 0.58 65.8% 66.5% Fail Waiver 2 0.1% 5.59 85.44 1.10 11.43 58.43 1.41 -104.5% 31.6% 

Total Fail% 1,428 23.4% 1.45 17.65 1.92 1.09 11.37 1.80 24.9% 35.6% 
30 

Audit Sample Reductions and Projected Impact 

Table IV-5 shows the aggregate first and final results for the 95% of inspected audit sample 

vehicles tested using IM240. The average per vehicle emissions reductions from the audit 

sample are multiplied by the number of exempted clean screen vehicles to project the 

reductions that could have been achieved if the clean screen vehicles had instead been 

inspected at the stations. This amount is then compared to the total emission reductions from 

vehicles tested at stations to determine the impact of the Clean Screen program and the 

percentage of emissions reductions retained. 

For vehicles subject to the IM240 test, the Clean Screen program retained 98.4%, 96.9% and 

98.1% of the exhaust HC, CO and NOx reductions respectively. These reductions assume all 

vehicles are driven the same number of miles each year. Mileage adjusted emission 

reductions are calculated in section V. 

Table IV-5 Clean Screen Emissions Impact for Tailpipe Emissions 

C. Gas Cap Evaporative Emissions 

The evaporative emissions test used in the I/M Program is a gas cap pressure test. Leaking 

gas caps allow evaporated gasoline (HC) to escape from vehicle gas tanks into the 

Vehicles HC g/mi CO g/mi NOx g/mi

Audit Sample 4,234

Mean Initial 0.093 1.744 0.277

Mean Final 0.090 1.638 0.272

Emissions reduction 0.004 0.106 0.004

Clean Screens 222,368

Potential Reductions 863 23,507 992 

Station Vehicles 869,433

Mean Initial 0.290 3.967 0.623

Mean Final 0.229 3.132 0.564

Emissions reduction 0.061 0.835 0.059

In station reductions 53,088 726,166 51,003 

Combined CS & Stn 1,091,801 53,951 749,673 51,995 

Clean Screen Impact 1.6% 3.1% 1.9%

Retained Reductions 98.4% 96.9% 98.1%
31 

atmosphere. The impact of leaking gas caps on the Clean Screen program is only evaluated in 

this report in terms of the failure rate, not in terms of repairable gas cap emissions reductions3

. 

Figure IV-1 compares the average gas cap failure rate of the Clean Screen audit sample 

vehicles to the average failure rate of the non-audit vehicles tested at stations. The failure rate 

of vehicles exempted via Clean Screen methods was 15% lower than the failure rate of 

vehicles receiving a station-based test (See Figure IV-1). This result is expected because 

remote sensing is directed towards measuring tailpipe emissions. A gas cap evaporative leak 

has to be quite large to be detected by RSD units. Clean screen models were newer than the 

overall tested fleet. 

Figure IV-1 Gas Cap Pressure Failure Rates 

Using the fail rates identified in the audit sample, Table IV-6 shows the projected gas cap 

failures that would have been found in the exempted clean screen vehicles. These projected 

gas cap failures are added to the actual gas cap failures identified in initial inspections at the 

test stations to provide the total possible gas cap failure rate for the program. Vehicle counts 

in Figure IV-6 are higher than IV-5 because they include gas cap tests on vehicles tested using 

idle tests as well as those tested using IM240. Vehicles with a redeemed Clean Screen notice 

account for 17.1% of the total possible gas cap failures. Therefore, 82.9% of evaporative gas 

cap HC emission reductions were retained. 

 

3

 Although the gas cap leak rates are measured in the I/M Program, it is not clear that leak rates are directly related to the 

amount of evaporative HC emissions released from the gas tank. A small pressure leak may have the same effect as a 

large pressure leak, as long as it is sufficient to release internal gas tank pressure over a period of an hour or so. 

0.0%

0.5%

1.0%

1.5%

2.0%

2.5%

3.0%

3.5%

4.0%

4.5%

Pressure Failure Missing Cap

Nature of Failure

2013 Gas Cap Pressure Failure Rates

Clean Screen Station
32 

In general, it is desirable to use direct measurements of emissions to evaluate program 

performance rather than a model. Unlike exhaust emissions that are directly measured using 

tailpipe tests, however, emissions rates from gas caps cannot easily be directly measured. 

Emissions rates of vapor leaks are typically determined in a test laboratory by enclosing a 

vehicle in a sealed compartment and measuring the emissions released into the compartment 

over time, which is impractical for testing many vehicles. Therefore, the EPA mobile source 

emissions model, MOVES, was used to estimate the fraction of emissions benefits derived 

from gas cap inspections. 

CDPHE provided results from MOVES models of the benefits of the I/M program for 2013. 

The projected average reduction in HC emissions of the area fleet was 0.128 g/mi. This was 

comprised of 0.118 g/mi resulting from exhaust emissions inspections and 0.010 g/mi from 

the Gas Cap testing. The measured I/M exhaust reductions (see section V) were 498.8 tons. 

Assuming the 0.118 g/mi corresponded to 498.8 tons, the Gas Cap related HC reductions were 

projected to be 40.8 tons. These results are shown in Table IV-7. The RapidScreen impact 

was projected as 7.0 tons or 1.3% of the I/M program reductions. 

Table IV-6 Clean Screen Impact on Evaporative HC Emissions 

Table IV-7 Gas Cap Related Benefit Tons 

Initial Tests

Pressure 

Failure

Missing 

Cap

Total 

Fails

RapidScreen Audit 4,460 149 4 153 

3.3% 0.1% 3.4%

Projected RapidScreen 233,760 7,809 210 8,019 

Station GC Tests 958,107 37,491 1,345 38,836 

3.9% 0.1% 4.1%

Total Program 1,191,867 45,300 1,555 46,855 

RapidScreen Impact 19.6% 17.2% 13.5% 17.1%

Retained Reductions 80.4% 82.8% 86.5% 82.9%

MOVES Estimates (from CDPHE)

2013 

MOVES 

g/mi HC

I/M 

2013 

HC tons

I/M Exhaust emission reductions 0.118 498.8

Projected Gas Cap Evap Emissions reductions 0.010 40.7

I/M Program total HC reductions 0.128 539.6

Gas Cap Evap RapidScreen impact 17.1% 0.002 7.0

% of I/M program HC benefit 1.3%
33 

D. Hybrid RSD-LEI vs. 2-hit RSD 

Envirotest compared the effectiveness of the ‘Hybrid’ and ‘2-RSD’ screening methods. The 

Hybrid method uses a single RSD measurement and a low emitter index (LEI) table. The 2-

RSD method uses two RSD measurements. 

The audit sample of vehicles with IM240 tests contained 2,832 vehicles screened using the 2-

RSD method and 1,402 vehicles screened using Hybrid RSD-LEI method. Table IV-8 shows 

the emissions reductions for these two samples and the average for all vehicles inspected at 

stations. Figures IV-2 and IV-3 show the average initial emissions and emissions reductions 

for each sample. 

The 2-RSD method audit vehicles had initial emissions that were 41%, 53% and 54% of the 

overall I/M fleet average for HC and CO and NOx respectively. These percentages were 

similar to the equivalent percentages in 2012 of 42%, 50% and 56% respectively. 

The Hybrid RSD-LEI method audit vehicles had lower initial emissions that were 30%, 44% 

and 42% of the I/M fleet average for HC and CO and NOx respectively. These percentages 

were higher than the 2012 equivalents of 26%, 38% and 39% 

Average I/M emissions reductions for the 2-RSD audit vehicles were 1.9%, 3.5% and 0.7% of 

fleet average initial emissions for HC and CO and NOx respectively. The comparable 

percentages in 2012 were 3.8%, 3.4% and 3.0%. 

Average emissions reductions for the Hybrid RSD-LEI audit vehicles were 0.8%, 2.1% and 

1.1% of fleet average initial emissions for HC and CO and NOx respectively. The 

comparable 2012 percentages were 0.8%, 0.9% and 0.1%. Average reductions in station 

tested vehicles were 24.4%, 23.9% and 10.7% for HC, CO and NOx respectively. 

The Hybrid RSD-LEI audit vehicles had lower initial emissions of HC, CO and NOx and 

smaller reductions than the 2-RSD audit vehicles. Consideration should be given to adjusting 

the 2-RSD standards. The RSD-LEI method standards are in part automatically adjusted by 

annual updates to the LEI table. 
34 

Table IV-8 Average Emissions per Vehicle 

 

Figure IV-2 Average Initial IM240 Emissions 

Vehicle IM240 Tailpipe Emissions

Sample Vehicles HC g/mi CO g/mi NOx g/mi

I/M vehicle initial mean 

emissions 0.248 3.496 0.549

2-RSD Audits 2,832

Mean Initial 0.103 1.845 0.299

Mean Final 0.098 1.723 0.296

Emissions reduction 0.005 0.122 0.004

 % of I/M vehicle initial mean emission 1.9% 3.5% 0.7%

Hybrid Audits 1,402

Mean Initial 0.075 1.540 0.231

Mean Final 0.073 1.466 0.225

Emissions reduction 0.002 0.074 0.006

 % of I/M vehicle initial mean emission 0.8% 2.1% 1.1%

All Station Tests 869,433

Mean Initial 0.290 3.967 0.623

Mean Final 0.229 3.132 0.564

Emissions reduction 0.061 0.835 0.059

 % of I/M vehicle initial mean emission 24.6% 23.9% 10.7%

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

Station

2-RSD

RSDLEI

g/mi

HC

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

Station

2-RSD

RSDLEI

CO

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

Station

2-RSD

RSDLEI

NOx
35 

Figure IV-3 Average IM240 Emissions Reductions 

 

0.00

0.02

0.04

0.06

0.08

Station

2-RSD

RSD-LEI

g/mi

HC

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Station

2-RSD

RSD-LEI

CO

0.00

0.02

0.04

0.06

0.08

0.10

Station

2-RSD

RSD-LEI

NOx
36 

V. Estimate of Overall I/M Program Benefits and Clean Screen 

Impact 

Overall I/M program emission reductions derive from two main components: 

○ Reductions resulting directly from I/M inspections and consequent repairs; 

○ Reductions from repair activities performed in anticipation of an I/M inspection. 

In previous years, it was assumed the vast majority of emissions reductions were directly 

measurable by comparing the initial and final I/M inspection emissions results, i.e. the first 

component described above. This report uses the same methodology. However, most 

vehicles tested were equipped with OBD-II malfunction indicator lights and many repairs of 

these vehicles are performed in response to warning lights before the initial inspection. The 

benefits of these repairs are not directly measurable in the program testing. 

The Clean Screen disbenefit can be projected directly from the emissions testing of the audit 

sample. There may be unmeasured offsetting benefits if the Clean Screen program 

encourages owners to maintain malfunctioning vehicles sooner than otherwise. 

For this report, measured I/M exhaust emissions benefits were projected from the IM240 and 

Idle emissions tests. In the case of Idle tests, idle test emission concentrations were converted 

to equivalent IM240 g/mi emissions. 

For each model year, the IM240 g/mi emissions values were weighted by the annual vehicle 

miles traveled to project the emissions inventory for initial and final test and, hence, the direct 

program benefits. 

The following sections project the directly measured tons of emissions and reductions 

A. Conversion of Idle Tests to IM240 Equivalent emissions 

On-road remote sensing emissions of vehicles inspected at I/M stations have been used to 

project IM240 equivalent values for Idle test emissions. 

The idle test procedure includes a low-speed idle and a high speed idle at 2500rpm. Vehicles 

model year 1980 and older are required to pass the low-speed idle while 1981 and newer 

models must pass both the low-speed and the high-speed tests. 

Figures V-1 and V-2 show the correlation between Idle tests and on-road HC and CO 

emissions of the same vehicles. Results are averaged by model year. Average initial and 

final test emissions were used for vehicles initially failing and retested. Model years were 

grouped together for 1965-and-older, 1966 to 1970, 1971 to 1975, 1976 to 1981, 1982 to 

1985, 1986 to 1990 and 2004-and-newer. Even with these groups, there were less than 100 

matching RSD measurements for Passenger vehicles in groups from 1982 to 1998. There 

were several hundred matching RSD measurements for each truck group. Trend lines were 

plotted with an intercept of zero to obtain RSD / Idle Test emissions ratios. 
37 

Similarly, Figure V-3 shows the correlation between IM240 and on-road emissions. Trend 

lines were plotted with an intercept of zero for HC and CO emissions to obtain IM240 / RSD 

emissions ratios. The results are summarized in Tables V-1 and V-2. 

Figure V-1 RSD vs. Idle Test Emissions 

Table V-1 Low Speed Idle to IM240 

Truck Idle Test and Matching Vehicle 

RSD Emissions

 (RSD N=57,867)

y = 1.0336x

R2

 = 0.9242

0

100

200

300

400

500

600

700

800

900

0 100 200 300 400 500 600 700 800

Idle HC ppm

RSD HC ppm

Passenger Idle Test and Matching

Vehicle RSD Emissions

 (RSD N=8,843)

y = 1.1007x

R2

 = 0.8169

0

100

200

300

400

500

600

- 100 200 300 400 500 600

Idle HC ppm

RSD HC ppm

Passenger Idle Test and Matching

Vehicle RSD Emissions

 (RSD N=8,843)

y = 1.3267x

R2

 = 0.712

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0.0 1.0 2.0 3.0 4.0

Idle CO %

RSD CO %

Truck Idle Test Test and Matching

Vehicle RSD Emissions

 (RSD N=57,867)

y = 1.5121x

R2

 = 0.7963

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

0.0 0.5 1.0 1.5 2.0 2.5 3.0

Idle CO %

RSD CO %

Low Speed Idle test to IM240 Projection

Passenger HC HC R2 CO CO R2

RSD / Idle 1.1007 0.81 1.3267 0.71

IM240 / RSD 0.0087 0.98 15.947 0.92

IM240 / Idle 0.0096 21.1569

Truck HC HC R2 CO CO R2

RSD / Idle 1.0336 0.92 1.5121 0.8

IM240 / RSD 0.0111 0.98 18.765 0.94

IM240 / Idle 0.0115 28.3746
38 

Figure V-2 RSD vs. 2500 Idle Test Emissions 

Table V-2 High Speed Idle to IM240 

Using the ratios derived above, IM240 g/mi equivalent emissions were projected for the 

vehicles tested with the idle test procedure. The low speed idle results were used to estimate 

emissions reductions as all model year vehicles tested at idle were required to pass the low 

speed idle test. 

Model Year Average Truck Idle 2500 Test and 

Matching Vehicle RSD Emissions

 (RSD N=57,867)

y = 1.548x

R2

 = 0.927

0

100

200

300

400

500

600

700

800

900

0 100 200 300 400 500 600 700 800

Idle HC ppm

RSD HC ppm

Model Year Average Passenger Idle 2500 Test 

and Matching Vehicle RSD Emissions (RSD 

N=8,843)

y = 1.5353x

R2

 = 0.8565

0

100

200

300

400

500

600

0 100 200 300 400 500 600

Idle HC ppm

RSD HC ppm

Model Year Average Passenger Idle 2500 Test 

and Matching Vehicle RSD Emissions (RSD 

N=8,843)

y = 1.1789x

R2

 = 0.8169

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0.0 1.0 2.0 3.0 4.0

Idle CO %

RSD CO %

Model Year Average Truck Idle 2500 Test and 

Matching Vehicle RSD Emissions

 (RSD N=57,867)

y = 1.4699x

R2

 = 0.8185

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

Idle CO %

RSD CO %

2500 RPM Idle test to IM240 Projection

Passenger HC HC R2 CO CO R2

RSD / 2500 1.5353 0.86 1.1789 0.82

IM240 / RSD 0.0087 0.98 15.947 0.92

IM240 / 2500 0.0134 18.7999

Truck HC HC R2 CO CO R2

RSD / 2500 1.548 0.93 1.4699 0.82

IM240 / RSD 0.0111 0.98 18.765 0.94

IM240 / 2500 0.0172 27.5827
39 

Figure V-3 RSD vs. IM240 Test Emissions 

Model Year Average Passenger IM240 Test and 

Matching Vehicle RSD Emissions

 (RSD N=449,842)

y = 0.0087x

R2

 = 0.9812

0.0

0.5

1.0

1.5

2.0

2.5

0 50 100 150 200 250

RSD HC ppm

IM240 HC g/mi

Model Year Average Passenger IM240 Test and 

Matching Vehicle RSD Emissions

 (RSD N=449,842)

y = 15.947x

R2

 = 0.9229

0

5

10

15

20

25

30

0.0 0.3 0.5 0.8 1.0 1.3 1.5

RSD CO %

IM240 CO g/mi

Model Year Average Passenger IM240 Test and 

Matching Vehicle RSD Emissions

 (RSD N=449,842)

y = 0.0016x + 0.1754

R2

 = 0.9885

0.0

0.5

1.0

1.5

2.0

2.5

0 250 500 750 1000 1250 1500

RSD NO ppm

IM240 NOx g/mi

Model Year Average Truck IM240 Test and 

Matching Vehicle RSD Emissions

 (RSD N=423,746)

y = 0.0111x

R2

 = 0.9756

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

0 50 100 150 200 250 300 350 400

RSD HC ppm

IM240 HC g/mi

Model Year Average Truck IM240 Test and 

Matching Vehicle RSD Emissions

 (RSD N=423,746)

y = 18.765x

R2

 = 0.9368

0

10

20

30

40

50

60

0.0 0.5 1.0 1.5 2.0 2.5 3.0

RSD CO %

IM240 CO g/mi

Model Year Average Truck IM240 Test and 

Matching Vehicle RSD Emissions

 (RSD N=423,746)

y = 0.0016x + 0.3013

R2

 = 0.9785

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0 500 1000 1500 2000

RSD NO ppm

IM240 NOx g/mi
40 

B. Annual Mileage Weighting 

Because of data entry errors and odometer rollover on older, high mileage vehicles, obtaining 

estimates of annual mileage from the I/M Program odometer readings for each model year 

and type of vehicle is not recommended. To avoid these problems, annual mileages for 

vehicles were taken from the 2008 ERG report on Colorado mileage accumulation rates7

. 

The estimated annual mileages are shown in Table V-3 for LDGVs and LDGTs. In Table VI3 the mileage accumulation rates for LDGT2, 3 and 4 were weighted together to obtain a 

single LDGT value. This table indicates that newer model year vehicles are driven more miles 

annually than older vehicles. It also indicates that 1998 and newer model year LDGTs, which 

emit greater masses of pollution than LDGVs are driven more miles annually than 1998 and 

newer model year LDGVs. 

` 

Table V-3 Estimated Annual Mileage in 2013 

Year LDGV LDGT

1983 4,304 4,550 

1984 4,304 4,554 

1985 4,304 4,562 

1986 4,434 4,583 

1987 4,481 4,630 

1988 4,502 4,668 

1989 4,552 4,741 

1990 4,780 4,851 

1991 5,088 5,019 

1992 5,430 5,256 

1993 5,672 5,519 

1994 6,002 5,824 

1995 6,331 6,135 

1996 6,653 6,471 

1997 6,974 6,940 

1998 7,369 7,437 

1999 7,764 7,863 

2000 8,188 8,345 

2001 8,613 8,900 

2002 9,032 9,502 

2003 9,450 10,087 

2004 9,905 10,727 

2005 10,360 11,245 

2006 10,746 11,817 

2007 11,132 12,303 

2008 11,870 12,834 

2009 12,023 13,215 

2010 12,307 13,433 

2011 12,357 13,514 

2012 11,600 12,428 

2013 9,650 8,995 
41 

C. Annual Emissions Reductions 

Annual tons of emissions were projected for vehicle type and model year by multiplying the 

numbers of vehicles by annual mileage and average g/mi emission levels. Results were 

projected for initial tests and final tests to determine the initial and final tons of emissions and, 

therefore, the tons of reduction. The results are listed in Appendix B for IM240 and Idle tests. 

Table V-4 first shows the reductions from the Clean Screen audit tests. Based on the audit 

tests, the second part of the table projects the potential reductions from the Clean Screen 

vehicles if all vehicles with redeemed Clean Screen notices had been tested at a station. The 

third part of the table shows the reductions from the vehicles tested at inspection stations, 

which includes the Clean Screen audit vehicles. The total potential reductions from the 

program are the combination of the potential reductions from the Clean Screened vehicles 

plus the actual reductions from the vehicles tested at stations. 

In Table IV-4, Clean Screen effectiveness was expressed without reference to the annual 

vehicle miles traveled (VMT) by each model year of vehicles. The more complete analysis in 

Table V-4 shows the Clean Screen program effectiveness when the VMT and Gas Cap4

estimates are factored in. During 2013, the Clean Screen program retained 97.3%, 96.7% and 

97.6% respectively of potential HC, CO and NOx emission reductions in vehicles subject to 

testing. 

For vehicles initially tested in calendar year 2013, the I/M Program is projected to have 

eliminated 559.0 tons of HC, 6,924.4 tons of CO and 414.8 tons of NOx for one year of 

vehicle travel – based on the IM240 driving cycle. 

Because the program is biennial, these reductions are approximately half of the reductions 

that would be measured over a full two-year cycle of the program. 

The tons of reductions cited here do not relate directly to the total mobile emissions inventory. 

The reductions cited are for tailpipe emissions and are in terms of the IM240 driving cycle. 

State Implementation Plan reductions are based on different driving cycles, are subject to 

many adjustments for speed, road type, temperature, air conditioning loads, etc., and therefore 

are larger than the IM240 measured reductions. 

As noted earlier, the reductions shown do not include reductions from maintenance actions 

performed on vehicles before their initial inspection. These may be quite substantial, 

especially for OBD-II vehicles that turn on the check engine light to alert owners to problems. 

 

4

 The evaporative emissions have not been adjusted for mileage but the effect of an adjustment would be small. Gas cap 

failures are more evenly distributed by age than tailpipe failures and only part of the evaporative emissions are running 

losses dependent on miles traveled. 
42 

Table V-4 Estimated Annual Tons of Reduction (IM240 and Idle Tested Vehicles 

* NOx is not reported for idle tests. 

Table V-4 also shows that, during calendar year 2013, 233,760 vehicles were exempted 

through Clean Screen, and 951,115 vehicles received a station test. Therefore, 19.7% of the 

1,184,875 unique vehicles were Clean Screened. 

If the fraction of Clean Screen vehicles had been 30% of vehicles subject to inspection there 

would have been 355,463 Clean Screens and 829,413 Station tests. Assuming this increase 

was achieved by increasing on-road fleet coverage rather than by relaxing the Clean Screen 

standards, the projected emissions retained would have been 95.9%, 94.5% and 95.9% 

respectively of potential HC, CO and NOx tailpipe emission reductions. 

 Audit Vehicle Reductions (IM240 tons/yr)

Audit Tests

Unique 

Vehicles HC CO NOx

Enhanced IM240 4,234 0.14 4.33 0.18

Potential from RS Vehicles (IM240 tons/yr)

RapidScreen

Unique 

Vehicles HC CO NOx

Enhanced Area 233,760 8.0 239.2 10.1

Gas Cap estimate from Mobile6 7.4

Station Reductions (IM240 tons/yr)

Station I/M Vehicles

Unique 

Vehicles HC CO NOx

Enhanced IM240 869,433 368.9 5,133.9 414.8

Enhanced Idle* 81,682 154.2 1,790.5

Gas Cap scaled from MOVES 35.9

 559.0 951,115 6,924.4 414.8 

Total Potential Reductions 574.4 7,163.6 424.8

RapidScreen Exhaust Impact 1.4% 3.3% 2.4%

Rapidscreen Gas Cap Impact 1.3%

Retained Reductions 97.3% 96.7% 97.6%
43 

VI. IM240 Projected Emissions by Model Year 

Figures VI-1 through VI-6 show the annual emissions inventories and reductions by model 

year and vehicle type for the vehicles tested in 2013 at stations, based on the IM240 driving 

cycle. The projected exhaust emissions inventory for the Clean Screen vehicles and Idle 

tested vehicles are also shown. The biennial testing cycle of the Enhanced area causes the 

difference between the sizes of the bars for odd model year vehicles vs. even model year 

vehicles. 

Not included in these charts: 

 most 2010 and newer models not yet subject to inspection; 

 any estimate of pre-inspection emission reductions; 

 NOx emissions for 81,682 vehicles tested with the idle test: 1981 and older models 

12,891 (16%), 1982 and newer trucks 64,174 (78%), and 1982 & newer passenger 

vehicles 4,617 (6%). 

The Figures VI-1 to 6 illustrate that 1995 and older vehicles, which are fewer in number and 

driven fewer miles each year, still contribute many tons of excess emissions in the I/M area – 

especially old trucks. 
44 

Figure VI-1 LDGV HC Reductions and Remaining Emissions 

Figure VI-2 LDGT HC Reductions and Remaining Emissions 

0

50

100

150

200

250

P 1965&older

P 1966-70P 1971-75P 1976-81

P 1982P 1983P 1984P 1985P 1986P 1987P 1988P 1989P 1990P 1991P 1992P 1993P 1994P 1995P 1996P 1997P 1998P 1999P 2000P 2001P 2002P 2003P 2004P 2005P 2006P 2007P 2008P 2009P 2010P 2011P 2012P 2013

IM240 Equivalent Exhaust Tons Per Year in 2013

Passenger HC

Idle Reduction HC

IM240 Reduction HC

Idle Final HC

IM240 Final HC

Clean Screen Vehicles HC

0

50

100

150

200

250

T 1965&older

T 1966-70T 1971-75T 1976-81

T 1982T 1983T 1984T 1985T 1986T 1987T 1988T 1989T 1990T 1991T 1992T 1993T 1994T 1995T 1996T 1997T 1998T 1999T 2000T 2001T 2002T 2003T 2004T 2005T 2006T 2007T 2008T 2009T 2010T 2011T 2012T 2013

IM240 Equivalent Exhaust Tons Per Year in 2013

Light Truck HC

Idle Reduction HC

IM240 Reduction HC

Idle Final HC

IM240 Final HC

Clean Screen Vehicles HC
45 

Figure VI-3 LDGV CO Reductions and Remaining Emissions 

Figure VI-4 LDGT CO Reductions and Remaining Emissions 

0

500

1,000

1,500

2,000

2,500

P 1965&older

P 1966-70P 1971-75P 1976-81

P 1982P 1983P 1984P 1985P 1986P 1987P 1988P 1989P 1990P 1991P 1992P 1993P 1994P 1995P 1996P 1997P 1998P 1999P 2000P 2001P 2002P 2003P 2004P 2005P 2006P 2007P 2008P 2009P 2010P 2011P 2012P 2013

IM240 Equivalent Exhaust Tons Per Year in 2013

Passenger CO

Idle Reduction CO

IM240 Reduction CO

Idle Final CO

IM240 Final CO

Clean Screen Vehicles CO

0

500

1,000

1,500

2,000

2,500

T 1965&older

T 1966-70T 1971-75T 1976-81

T 1982T 1983T 1984T 1985T 1986T 1987T 1988T 1989T 1990T 1991T 1992T 1993T 1994T 1995T 1996T 1997T 1998T 1999T 2000T 2001T 2002T 2003T 2004T 2005T 2006T 2007T 2008T 2009T 2010T 2011T 2012T 2013

IM240 Equivalent Exhaust Tons Per Year in 2013

Light Truck CO

Idle Reduction CO

IM240 Reduction CO

Idle Final CO

IM240 Final CO

Clean Screen Vehicles CO
46 

Figure VI-5 LDGV NOx Reductions and Remaining Emissions 

Figure VI-6 LDGT NOx Reductions and Remaining Emissions 

0

50

100

150

200

250

300

350

400

450

500

P 1965&older

P 1966-70P 1971-75P 1976-81

P 1982P 1983P 1984P 1985P 1986P 1987P 1988P 1989P 1990P 1991P 1992P 1993P 1994P 1995P 1996P 1997P 1998P 1999P 2000P 2001P 2002P 2003P 2004P 2005P 2006P 2007P 2008P 2009P 2010P 2011P 2012P 2013

IM240 Equivalent Exhaust Tons Per Year in 2012

Passenger NOx

Idle Reduction NOx n/a

IM240 Reduction NOx

Idle Final NOx n/a

IM240 Final NOx

Clean Screen Vehicles NOx

0

50

100

150

200

250

300

350

400

450

500

T 1965&older

T 1966-70T 1971-75T 1976-81

T 1982T 1983T 1984T 1985T 1986T 1987T 1988T 1989T 1990T 1991T 1992T 1993T 1994T 1995T 1996T 1997T 1998T 1999T 2000T 2001T 2002T 2003T 2004T 2005T 2006T 2007T 2008T 2009T 2010T 2011T 2012T 2013

IM240 Equivalent Exhaust Tons Per Year in 2012

Light Truck NOx

Idle Reduction NOx n/a

IM240 Reduction NOx

Idle Final NOx n/a

IM240 Final NOx

Clean Screen Vehicles NOx
47 

VII. RapidScreen Benefits 

Rapidscreen provided benefits to vehicle owners of $5.15M through reduced time and 

expense associated with eliminated inspection station visits. The elimination of station 

inspections also yielded net savings in greenhouse gases and 195,600 gallons of gasoline. 

This section summarizes the operational costs and benefits of the Rapidscreen program. 

A. Greenhouse Gas and Pollutants from Clean Screen Operations 

The following were considered in deriving the net emissions, greenhouse gas and fuel use 

associated with the RapidScreen program: 

- RSD van operations;

- RSD generators;

- RSD unit calibration and audit gases;

- Reductions from eliminated trips to inspection stations. 

Table VII-1 summarizes these amounts. 

Table VII-1 Reductions in Greenhouse Gases and Pollutants from RapidScreen Operations 

1. RapidScreen Operating Vehicles 

Emissions and fuel usage of RSD vans, audit trucks and maintenance vehicles associated with 

the RapidScreen program were developed from the average IM240 emissions of each vehicle 

from the most recent inspections performed from 2010 through 2013. Idle test emissions 

were converted to IM240 g/mi using the conversion factors described in Section V. 

Emissions were scaled up to match MOVES estimates of running emissions vs. IM240 using 

scaling factors of 1.0 for hydrocarbons, 1.92 for CO and 2.23 for NOx. Odometer changes 

were pro-rated to provide annual mileages. Fuel use was calculated using EPA city fuel 

Activity HC t/yr CO t/yr NOx t/yr CO2 t/yr Fuel gal.

RapidScreen Operations

RapidScreen operating vehicles (vans, audit

trucks, maintenance) 0.132 1.64 0.027 91.1 10,208

Generators 0.943 24.08 0.081 59.4 10,097

Calibration and audit gases 0.005 0.05 0.003 0.5

Total Rapidscreen operations 1.080 25.77 0.111 150.9 20,305

RapidScreen Vehicle Emission Reductions

Station trip, waiting & testing 0.445 12.24 2.148 1925.9 215,905

Net benefit (cost) (0.63) (13.53) 2.037 1774.9 195,600
48 

economies for the vehicle models or similar models. CO2 tons were calculated at the rate of 

8.92 x 10-3 tons per gallon (http://www.epa.gov/cleanenergy/energy-resources/refs.html). 

2. Generators 

Typical emissions and CO2 grams over a four minute period were obtained by collecting 

emissions from two generators using lane IM240 equipment. Emissions were collected from 

the generator while another vehicle was driven on the dynamometer. Emissions and CO2

grams were then multiplied by 15 to obtain g/hour and by the Active Collection Van Hours 

from Table III-1. Fuel gallons were back calculated from CO2 tons. 

Envirotest is in the process of replacing existing generators with newer, lower emitting 

models that would eliminate 67% of HC emissions and up to 98% of the generator NOx 

emissions. 

3. Calibration and Audit Gases 

Calibration and Audit Gas emissions were calculated directly from the use estimates 

presented in Table VII-2. The liters of calibration and audit gases at 70F and normal pressure 

were multiplied by the pollutant concentration percentages and by the pollutant mass per liter 

to obtain tons. 

Table VII-2 Calibration and Audit Gas Emissions 

4. RapidScreen Vehicle Emissions Reductions 

The RapidScreen program eliminated the need for 233,760 station inspections that would 

otherwise require travel, waiting and inspection. 

RSD VANS

AL

Cyls

BL

Cyls

CL

Cyls

Liters at

70F NP

CO

%

CO2

% HC % NO %

HC

PPM

NOX

PPM

CO

tons

CO2

tons

HC

tons

NO

tons

Calibration 240 30 0 1,028,820 3.00 12.90 0.15 0.15 1500 1500 0.0425 0.2874 0.0033 0.0023

2 Point Audit 80 10 342,940 0.50 14.70 0.04 0.10 400 1000 0.0024 0.1092 0.0003 0.0005

ATP / DOR

A 12 0 47,916 0.00 15.05 0.00 0.00 0 0 0.0000 0.0156 0.0000 0.0000

F 12 0 16 61,964 5.00 11.55 0.60 0.03 6000 250 0.0043 0.0155 0.0008 0.0000

G 12 0 47,916 0.20 14.91 0.01 0.15 100 1500 0.0001 0.0155 0.0000 0.0001

H 12 0 47,916 0.30 14.84 0.02 0.10 200 1000 0.0002 0.0154 0.0000 0.0001

J 12 0 16 61,964 0.50 14.70 0.04 0.10 400 1000 0.0004 0.0197 0.0001 0.0001

K 12 0 47,916 1.00 14.34 0.05 0.03 500 300 0.0007 0.0149 0.0001 0.0000

L 12 0 47,916 1.50 13.99 0.07 0.01 700 100 0.0010 0.0145 0.0001 0.0000

Q 12 0 16 61,964 3.00 12.92 0.11 0.05 1100 500 0.0026 0.0173 0.0001 0.0000

Total 416 40 48 1,797,232 0.0541 0.5249 0.0048 0.0031

Capacities and g/l

AL

Cyls

BL

Cyls

CL

Cyls

CO

%

CO2

% HC % NO %

Cylinder  L @2000psi 29.5 15.7 5.9 Mol. Wt 28 44 44 30

Liters gas at 70F NP 3993 2350 878 g/l 1.3 2.0 2.0 1.3
49 

The average round trip to a station was estimated to be 9.5 miles. For every two minutes a car 

is idling, it uses about the same amount of fuel it takes to go about one mile according to the 

Consumer Energy Center (http://www.consumerenergycenter.org/myths/idling.html). This 

implies the average waiting time of 13.5 minutes was equivalent to 6.8 miles of driving. The 

equivalent of another equivalent 2.2 miles of driving was spent moving through the inspection 

lane for a total equivalent of 18.5 miles per inspection. Eliminated trip/inspection emissions 

tons were calculated from the inspection mileage multiplied by the average IM240 g/mi 

emissions of the RapidScreen audit sample and the number of exempted vehicles. As noted 

above, IM240 emissions were scaled up to match MOVES estimates of running emissions vs. 

IM240. Gallons of fuel saved were estimated using an average of 20mpg. 

B. RapidScreen Vehicle Owner Savings 

Table VII-3 quantifies the RapidScreen benefits to vehicle owners. The average round trip to 

an inspection station was assumed to take an average of 28.5 minutes (9.5 miles at 20mph). 

Average wait and test times were both 13.5 minutes. The waiting and testing fuel 

consumption was estimated to be the equivalent of driving another 8.4 miles. Vehicle owner 

time was assumed to be worth half the Denver area average hourly wage of $25.05 per hour, 

or $12.53 per hour. 

Travel savings from were calculated at the IRS rate of 56.5c per mile per IRS Notice IR-2012-

95, Nov. 21, 2012. 

Total savings were $5.15M or $22.02 per vehicle. 

Table VII-3 RapidScreen Vehicle Owner Savings 

Activity Vehicles Minutes Hours Unit $ $'M

Station round trip @ 20mph 233760 28.5 111036 12.53 $     $      1.39

Testing 233760 13.5 52479 12.53 $     $      0.66

Waiting 233760 13.5 52596 12.53 $     $      0.66

Miles

Driving miles equiv. 233760 18.5 0.565 $     $      2.44

Total vehicle ownersavings 5.15 $      
50 

VIII. Recommendations 

In 2015, several program changes will be implemented that will affect the vehicles subject to 

testing and test procedures: 

 New models will be exempt for seven years vs. four years currently; 

 Models 8 to 11 years old will be tested by scanning the OBD status with a fallback to 

IM240 allowed for vehicles with no more than one out of a select group of OBD 

system monitors not set ready; 

 Models over 11 years old will continue to be tailpipe tested using IM240 or Idle. 

Currently clean screen notices are issued to 30% of subject vehicles due to renew registration. 

Unless changes are made to clean screen criteria, the 2015 program changes will act to reduce 

this percentage in two ways: 

 The percentage of vehicles qualifying for clean screen is highest among the newest 

three model years that will now be exempt and will reduce current clean screens by at 

least one third; 

 If/when the LEI is updated with OBD failure rates for 8 to 11 year old vehicles, the 

percentage of passing the screen will decrease dramatically. 

It is desirable to increase clean screen productivity provided the program remains compliant 

with the clean screen goals modeled using Mobile6. 

MIL-on rates in Colorado are currently higher than observed in other state I/M programs. As 

owners realize MIL-on is required, Colorado observed MIL-on rates should fall. Modeling 

using existing MIL-on rates therefore overstates the impacts of the transition for OBD 

inspected models. OBD testing of 8-11 year olds will affect fail rates but the extent will 

depend on the number of pre-inspection repairs obtained by vehicle owners in response to the 

new program rules. 

It is suggested 2015 should be a transitional year. The year will start using the current clean 

screen criteria with only minor changes such as a potential increase in the existing 2% RSDLEI fail cutpoint. This will be evaluated to determine whether adjusting the threshold, e.g. to 

5%, in fall of 2014 for 2015 renewal candidates, could increase motorist convenience and 

clean screens without materially affecting program emission reductions. 

In addition: 

 Recommended Reg 11 changes: 

o Permit periodic adjustments of the LEI fail % cutpoints as approved by 

CDPHE, e.g. in 2014 for IM240 tested models, and during 2015 for OBD 

tested models; 

o Allow a separate LEI OBD fail % cutpoint for the OBD tested RSD-LEI 

models; 
51 

 In order to provide emissions data on clean screen OBD tested models in 2015, set 

registration table flags set to force dual OBD and IM240 inspection of 8-11 year old 

models selected for clean screen audit. The IM240 being either a normal IM240 with 

fast-pass allowed, or, if operationally acceptable, a full IM240. These OBD model 

vehicles selected as part of the random 2% clean screen audit sample IM240’s may 

form part of the independently required 5% OBD-IM240 sample; 

 In order to create an adequate audit sample by end of June 2015 for a mid-year 

evaluation, and provided doing so will not materially increase wait times, increase the 

clean screen audit percentage to 3.5% or 4% during the first half of 2015 and reduce it 

to 0.5% or 0% during the second half year. This will allow appropriate LEI cutpoints 

to be developed in fall of 2015 for 2016 renewals. 
52 

References 

 

1

 “The Colorado Remote Sensing Program January – December 2011”, Envirotest report for the 

Colorado Department of Public Health and Environment, November 2012 

2 Colorado Air Quality Control Commission, “Regulation Number 11, Motor Vehicle Emissions 

Inspection Program”, http://www.cdphe.state.co.us/regulations/airregs/5CCR1001-13.pdf 

3 Colorado Department Of Public Health and Environment, Air Pollution Control Division, Mobile 

Sources Section, “Colorado On-road Vehicle Emissions Remote Sensing System (COVERS) 

Specifications” Amended July 2010 

4

 Klausmeier R., “Technical Note: Estimating Full IM240 Emissions Based on Fast Pass Emission 

Results”, November 2005 

5

 Wenzel, T. “Evaluation of Arizona’s Enhanced I/M Program”, Presented at the 9th CRC On-Road 

Vehicle Emissions Workshop. April 1999. 

6

 McClintock, P. “The Denver Remote Sensing Clean Screening Pilot”, Envirotest report for the 

Colorado Department of Health and Environment, December 1999. 

7

 “Colorado Mileage Accumulation Rates from VID Odometer Readings Draft Report” for CDPHE by 

Eastern Research Group, Inc. June 30, 2008 
Appendix A1 Colorado 2013 Transient Test Emissions Reductions

Unresolved fails remaining in area 33%

Model First Last Initial Final Reduction %

Year/Type Result Result Vehicles Fail% HC CO NOX HC CO NOX HC CO NOX

1982 Pass - 258 1.62 19.18 2.02 1.62 19.18 2.02 0.0% 0.0% 0.0%

P Fail Pass 59 17.2% 4.56 51.09 2.02 1.52 19.35 1.88 66.6% 62.1% 7.0%

Fail Unresolv. 26 7.6% 5.59 85.27 1.92 1.99 29.03 0.65 64.4% 66.0% 66.0%

Fail Waiver 1 0.3% 1.49 70.11 0.38 1.49 70.11 0.38 0.0% 0.0% 0.0%

Total Fail% 344 25.0% 2.42 29.80 2.00 1.63 20.10 1.88 32.7% 32.5% 6.0%

1983 Pass - 462 1.29 12.26 2.07 1.29 12.26 2.07 0.0% 0.0% 0.0%

P Fail Pass 98 16.0% 2.32 36.51 2.06 1.24 14.85 1.79 46.7% 59.3% 13.2%

Fail Unresolv. 49 8.0% 4.46 73.11 1.91 1.56 24.31 0.57 65.1% 66.7% 69.9%

Fail Waiver 3 0.5% 4.50 140.30 1.08 4.73 146.55 0.24 -5.0% -4.5% 77.6%

Total Fail% 612 24.5% 1.73 21.65 2.05 1.32 14.30 1.89 23.5% 33.9% 7.5%

1984 Pass - 619 1.23 11.35 1.92 1.23 11.35 1.92 0.0% 0.0% 0.0%

P Fail Pass 147 17.3% 2.86 39.51 1.97 1.44 14.26 2.05 49.7% 63.9% -4.4%

Fail Unresolv. 79 9.3% 5.47 75.77 1.82 1.73 23.32 0.59 68.4% 69.2% 67.3%

Fail Waiver 6 0.7% 5.14 112.15 1.64 4.98 116.14 1.55 3.2% -3.6% 5.9%

Total Fail% 851 27.3% 1.94 22.90 1.92 1.34 13.70 1.82 30.7% 40.2% 5.2%

1985 Pass - 1,094 1.05 10.84 1.89 1.05 10.84 1.89 0.0% 0.0% 0.0%

P Fail Pass 226 15.8% 2.21 31.01 2.12 1.09 9.71 1.93 50.7% 68.7% 8.8%

Fail Unresolv. 106 7.4% 3.92 58.15 1.79 1.34 19.49 0.58 65.8% 66.5% 67.5%

Fail Waiver 2 0.1% 5.59 85.44 1.10 11.43 58.43 1.41 -104.5% 31.6% -27.3%

Total Fail% 1,428 23.4% 1.45 17.65 1.92 1.09 11.37 1.80 24.9% 35.6% 6.2%

1986 Pass - 1,228 0.92 7.91 1.80 0.92 7.91 1.80 0.0% 0.0% 0.0%

P Fail Pass 199 13.1% 2.11 25.18 2.17 1.08 9.10 1.89 48.7% 63.9% 13.2%

Fail Unresolv. 90 5.9% 5.07 66.22 2.13 1.48 19.40 0.73 70.9% 70.7% 65.7%

Fail Waiver 3 0.2% 8.87 78.05 1.85 8.39 69.96 1.92 5.4% 10.4% -4.1%

Total Fail% 1,520 19.2% 1.34 13.76 1.87 0.99 8.87 1.75 26.0% 35.5% 6.4%

1987 Pass - 1,974 0.84 7.71 1.81 0.84 7.71 1.81 0.0% 0.0% 0.0%

P Fail Pass 273 11.6% 2.30 26.86 2.08 1.04 9.26 1.72 55.0% 65.5% 17.3%

Fail Unresolv. 96 4.1% 4.37 54.71 2.10 1.45 19.04 0.64 66.8% 65.2% 69.5%

Fail Waiver 7 0.3% 3.36 49.60 2.75 4.28 55.88 2.81 -27.6% -12.7% -1.9%

Total Fail% 2,350 16.0% 1.16 11.98 1.85 0.90 8.49 1.75 22.7% 29.1% 5.5%

1988 Pass - 1,798 0.74 7.84 1.59 0.74 7.84 1.59 0.0% 0.0% 0.0%

P Fail Pass 266 12.3% 2.69 27.10 1.87 0.94 8.74 1.66 65.1% 67.8% 10.9%

Fail Unresolv. 91 4.2% 4.34 39.25 2.05 1.37 12.28 0.68 68.4% 68.7% 67.0%

Fail Waiver 5 0.2% 4.45 31.72 3.32 4.45 39.36 1.99 0.1% -24.1% 39.9%

Total Fail% 2,160 16.8% 1.14 11.59 1.65 0.80 8.21 1.56 29.8% 29.2% 5.2%

1989 Pass - 3,208 0.72 7.90 1.61 0.72 7.90 1.61 0.0% 0.0% 0.0%

P Fail Pass 405 10.8% 2.12 24.65 1.86 0.89 8.60 1.61 58.1% 65.1% 13.4%

Fail Unresolv. 131 3.5% 3.84 42.15 2.14 1.16 14.00 0.74 69.8% 66.8% 65.4%

Fail Waiver 4 0.1% 4.00 119.43 0.31 4.01 119.56 0.36 -0.1% -0.1% -15.3%

Total Fail% 3,748 14.4% 0.99 11.03 1.65 0.76 8.31 1.58 23.0% 24.7% 4.6%

A1-1
Appendix A1 Colorado 2013 Transient Test Emissions Reductions

Unresolved fails remaining in area 33%

Model First Last Initial Final Reduction %

Year/Type Result Result Vehicles Fail% HC CO NOX HC CO NOX HC CO NOX

1990 Pass - 3,890 0.70 7.69 1.60 0.70 7.69 1.60 0.0% 0.0% 0.0%

P Fail Pass 526 11.4% 1.79 23.38 2.14 0.86 8.23 1.71 52.0% 64.8% 19.9%

Fail Unresolv. 176 3.8% 3.52 38.36 2.39 1.13 12.27 0.79 68.0% 68.0% 66.9%

Fail Waiver 8 0.2% 4.74 49.18 2.96 1.85 36.29 3.19 60.9% 26.2% -7.8%

Total Fail% 4,600 15.4% 0.94 10.73 1.70 0.74 7.98 1.59 21.6% 25.7% 6.5%

1991 Pass - 6,006 0.59 6.73 1.45 0.59 6.73 1.45 0.0% 0.0% 0.0%

P Fail Pass 832 11.7% 1.75 22.18 1.97 0.72 7.04 1.55 59.0% 68.3% 21.7%

Fail Unresolv. 273 3.8% 3.16 33.84 2.37 1.02 11.29 0.76 67.6% 66.6% 68.0%

Fail Waiver 18 0.3% 3.14 47.36 1.76 3.09 40.87 1.51 1.4% 13.7% 14.3%

Total Fail% 7,129 15.8% 0.83 9.67 1.55 0.62 7.02 1.44 24.5% 27.4% 7.3%

1992 Pass - 5,812 0.57 6.25 1.42 0.57 6.25 1.42 0.0% 0.0% 0.0%

P Fail Pass 790 11.5% 1.68 23.39 1.81 0.67 6.52 1.52 59.9% 72.1% 16.2%

Fail Unresolv. 256 3.7% 3.66 37.50 2.07 1.23 12.93 0.66 66.3% 65.5% 68.1%

Fail Waiver 15 0.2% 4.18 45.81 1.76 2.51 35.38 1.59 39.9% 22.8% 9.6%

Total Fail% 6,873 15.4% 0.82 9.47 1.49 0.61 6.60 1.41 25.7% 30.4% 5.8%

1993 Pass - 8,487 0.54 5.76 1.44 0.54 5.76 1.44 0.0% 0.0% 0.0%

P Fail Pass 995 10.1% 1.37 19.52 2.02 0.63 6.23 1.58 54.0% 68.1% 21.6%

Fail Unresolv. 330 3.4% 2.76 29.61 2.22 1.00 10.29 0.73 63.7% 65.2% 67.2%

Fail Waiver 18 0.2% 2.90 30.61 2.62 4.91 27.55 2.49 -69.3% 10.0% 4.9%

Total Fail% 9,830 13.7% 0.71 8.00 1.53 0.57 6.00 1.43 18.5% 25.0% 6.2%

1994 Pass - 9,146 0.42 5.10 1.16 0.42 5.10 1.16 0.0% 0.0% 0.0%

P Fail Pass 961 9.2% 1.50 17.95 1.71 0.52 5.60 1.26 65.0% 68.8% 26.2%

Fail Unresolv. 328 3.1% 3.13 29.41 2.19 1.01 9.47 0.72 67.9% 67.8% 67.3%

Fail Waiver 11 0.1% 5.19 39.70 2.36 4.78 34.41 2.28 8.0% 13.3% 3.4%

Total Fail% 10,446 12.4% 0.61 7.08 1.24 0.45 5.31 1.16 25.6% 25.0% 7.0%

1995 Pass - 14,190 0.40 4.70 1.01 0.40 4.70 1.01 0.0% 0.0% 0.0%

P Fail Pass 1,398 8.7% 1.23 15.74 1.61 0.48 5.10 1.19 60.7% 67.6% 25.7%

Fail Unresolv. 443 2.8% 2.38 22.40 2.31 0.78 7.60 0.75 67.2% 66.0% 67.7%

Fail Waiver 18 0.1% 1.69 15.15 3.01 1.77 9.66 2.60 -5.1% 36.3% 13.7%

Total Fail% 16,049 11.6% 0.53 6.16 1.10 0.42 4.82 1.02 20.7% 21.8% 7.3%

1996 Pass - 12,780 0.31 3.82 0.82 0.31 3.82 0.82 0.0% 0.0% 0.0%

P Fail Pass 1,301 9.0% 0.97 13.35 1.47 0.39 4.48 0.95 59.7% 66.5% 35.2%

Fail Unresolv. 309 2.1% 2.41 22.58 2.06 0.78 6.84 0.70 67.7% 69.7% 66.2%

Fail Waiver 15 0.1% 1.18 30.39 1.99 1.27 33.86 1.76 -7.6% -11.4% 11.7%

Total Fail% 14,405 11.3% 0.42 5.11 0.90 0.33 3.98 0.83 20.9% 22.2% 8.4%

1997 Pass - 19,145 0.30 3.79 0.75 0.30 3.79 0.75 0.0% 0.0% 0.0%

P Fail Pass 1,691 8.0% 0.83 12.81 1.28 0.36 4.43 0.88 57.0% 65.4% 31.1%

Fail Unresolv. 391 1.8% 1.93 24.10 2.02 0.66 8.29 0.66 66.0% 65.6% 67.6%

Fail Waiver 10 0.0% 2.26 23.14 2.84 4.10 29.06 2.91 -81.5% -25.6% -2.5%

Total Fail% 21,237 9.9% 0.37 4.89 0.81 0.31 3.94 0.76 16.2% 19.5% 7.0%

A1-2
Appendix A1 Colorado 2013 Transient Test Emissions Reductions

Unresolved fails remaining in area 33%

Model First Last Initial Final Reduction %

Year/Type Result Result Vehicles Fail% HC CO NOX HC CO NOX HC CO NOX

1998 Pass - 18,012 0.23 3.41 0.63 0.23 3.41 0.63 0.0% 0.0% 0.0%

P Fail Pass 1,762 8.7% 0.77 12.26 1.18 0.28 3.87 0.70 63.3% 68.5% 40.6%

Fail Unresolv. 377 1.9% 1.66 21.08 1.91 0.55 7.23 0.63 66.7% 65.7% 67.1%

Fail Waiver 13 0.1% 0.86 12.40 2.00 0.30 6.56 2.07 65.5% 47.1% -3.6%

Total Fail% 20,164 10.7% 0.30 4.52 0.70 0.24 3.52 0.64 20.9% 22.0% 9.4%

1999 Pass - 24,969 0.20 2.97 0.57 0.20 2.97 0.57 0.0% 0.0% 0.0%

P Fail Pass 2,307 8.3% 0.64 9.93 1.24 0.24 3.37 0.66 62.5% 66.1% 46.7%

Fail Unresolv. 399 1.4% 1.30 17.42 2.08 0.43 6.05 0.70 66.8% 65.3% 66.5%

Fail Waiver 9 0.0% 0.75 7.59 2.46 0.79 8.92 2.70 -4.5% -17.5% -9.7%

Total Fail% 27,684 9.8% 0.25 3.76 0.65 0.21 3.05 0.58 18.1% 18.9% 10.5%

2000 Pass - 24,217 0.15 2.52 0.46 0.15 2.52 0.46 0.0% 0.0% 0.0%

P Fail Pass 2,120 7.9% 0.58 9.32 1.29 0.21 3.23 0.58 63.9% 65.3% 55.5%

Fail Unresolv. 387 1.4% 1.45 16.73 2.20 0.46 5.52 0.72 68.6% 67.0% 67.3%

Fail Waiver 15 0.1% 2.13 22.26 2.20 0.62 10.64 2.59 70.7% 52.2% -17.9%

Total Fail% 26,739 9.4% 0.20 3.28 0.55 0.16 2.62 0.47 21.8% 19.9% 14.2%

2001 Pass - 29,978 0.10 2.08 0.31 0.10 2.08 0.31 0.0% 0.0% 0.0%

P Fail Pass 1,936 6.0% 0.55 7.65 1.05 0.16 2.63 0.42 70.4% 65.6% 59.7%

Fail Unresolv. 256 0.8% 1.21 14.44 2.07 0.38 4.81 0.71 68.3% 66.7% 65.7%

Fail Waiver 15 0.0% 2.72 9.24 3.07 0.80 8.45 3.06 70.7% 8.6% 0.5%

Total Fail% 32,185 6.9% 0.14 2.52 0.37 0.11 2.14 0.32 22.0% 15.0% 13.1%

2002 Pass - 25,025 0.09 2.42 0.27 0.09 2.42 0.27 0.0% 0.0% 0.0%

P Fail Pass 1,808 6.7% 0.45 7.05 0.88 0.13 2.38 0.37 70.8% 66.3% 58.6%

Fail Unresolv. 205 0.8% 1.06 13.39 2.33 0.36 4.11 0.78 65.7% 69.3% 66.5%

Fail Waiver 12 0.0% 0.49 9.61 2.63 0.67 8.74 2.51 -36.1% 9.0% 4.9%

Total Fail% 27,050 7.5% 0.12 2.82 0.32 0.09 2.43 0.28 21.9% 13.6% 14.3%

2003 Pass - 30,739 0.06 1.34 0.21 0.06 1.34 0.21 0.0% 0.0% 0.0%

P Fail Pass 1,576 4.9% 0.34 5.21 0.78 0.11 2.00 0.31 68.2% 61.6% 60.8%

Fail Unresolv. 137 0.4% 1.33 13.03 2.25 0.47 4.78 0.75 65.0% 63.3% 66.8%

Fail Waiver 4 0.0% 0.35 12.14 2.46 0.35 6.12 2.18 2.5% 49.6% 11.6%

Total Fail% 32,456 5.3% 0.08 1.58 0.24 0.06 1.39 0.22 19.5% 12.1% 12.0%

2004 Pass - 20,421 0.05 1.26 0.15 0.05 1.26 0.15 0.0% 0.0% 0.0%

P Fail Pass 1,172 5.4% 0.33 5.40 0.65 0.10 2.01 0.24 69.6% 62.8% 63.4%

Fail Unresolv. 111 0.5% 1.03 12.82 2.31 0.38 3.74 0.76 62.8% 70.8% 67.0%

Fail Waiver 6 0.0% 0.92 10.41 3.08 0.80 8.73 2.80 13.2% 16.2% 9.3%

Total Fail% 21,710 5.9% 0.07 1.55 0.19 0.06 1.32 0.16 21.8% 14.9% 15.9%

2005 Pass - 30,699 0.04 0.95 0.12 0.04 0.95 0.12 0.0% 0.0% 0.0%

P Fail Pass 1,444 4.5% 0.21 4.00 0.54 0.07 1.36 0.18 67.7% 65.9% 66.9%

Fail Unresolv. 73 0.2% 1.56 14.57 1.80 0.44 4.67 0.56 71.7% 68.0% 68.9%

Fail Waiver 1 0.0% 0.15 8.57 2.66 0.38 7.40 2.95 -156.2% 13.6% -10.8%

Total Fail% 32,217 4.7% 0.05 1.12 0.15 0.04 0.98 0.13 18.4% 12.6% 13.0%

A1-3
Appendix A1 Colorado 2013 Transient Test Emissions Reductions

Unresolved fails remaining in area 33%

Model First Last Initial Final Reduction %

Year/Type Result Result Vehicles Fail% HC CO NOX HC CO NOX HC CO NOX

2006 Pass - 21,813 0.04 1.12 0.10 0.04 1.12 0.10 0.0% 0.0% 0.0%

P Fail Pass 828 3.6% 0.26 4.99 0.87 0.07 1.48 0.18 73.6% 70.4% 79.7%

Fail Unresolv. 46 0.2% 1.60 13.86 2.56 0.49 4.35 0.77 69.4% 68.6% 69.8%

Fail Waiver 0 0.0% ------ - - -

Total Fail% 22,687 3.9% 0.05 1.29 0.13 0.04 1.14 0.11 19.1% 11.5% 21.4%

2007 Pass - 30,994 0.03 0.92 0.09 0.03 0.92 0.09 0.0% 0.0% 0.0%

P Fail Pass 759 2.4% 0.15 2.69 0.68 0.05 1.27 0.12 66.1% 52.5% 82.8%

Fail Unresolv. 27 0.1% 0.88 11.45 2.33 0.28 3.45 0.79 68.4% 69.9% 66.0%

Fail Waiver 0 0.0% ------ - - -

Total Fail% 31,780 2.5% 0.03 0.97 0.11 0.03 0.93 0.09 8.3% 4.2% 14.1%

2008 Pass - 15,681 0.03 1.00 0.08 0.03 1.00 0.08 0.0% 0.0% 0.0%

P Fail Pass 489 3.0% 0.23 3.40 0.85 0.06 1.39 0.12 75.7% 59.3% 85.6%

Fail Unresolv. 17 0.1% 0.92 9.54 2.71 0.30 3.07 0.92 68.0% 67.8% 66.0%

Fail Waiver 1 0.0% 0.56 7.45 3.42 0.49 7.89 3.27 11.4% -5.8% 4.6%

Total Fail% 16,188 3.1% 0.04 1.08 0.11 0.03 1.02 0.09 15.3% 6.2% 21.6%

2009 Pass - 26,667 0.03 0.95 0.08 0.03 0.95 0.08 0.0% 0.0% 0.0%

P Fail Pass 483 1.8% 0.15 2.36 0.72 0.05 1.33 0.09 67.8% 43.6% 87.1%

Fail Unresolv. 15 0.1% 1.36 15.55 3.10 0.46 5.75 0.91 66.4% 63.0% 70.5%

Fail Waiver 0 0.0% ------ - - -

Total Fail% 27,165 1.8% 0.03 0.98 0.09 0.03 0.96 0.08 7.4% 2.4% 13.1%

2010 Pass - 5,971 0.03 0.96 0.07 0.03 0.96 0.07 0.0% 0.0% 0.0%

P Fail Pass 90 1.5% 0.18 3.42 0.62 0.05 1.28 0.08 71.8% 62.5% 86.6%

Fail Unresolv. 9 0.1% 1.46 11.75 1.53 0.40 3.76 0.49 72.9% 68.0% 68.3%

Fail Waiver 0 0.0% ------ - - -

Total Fail% 6,070 1.6% 0.03 1.01 0.08 0.03 0.97 0.07 11.4% 4.3% 11.5%

2011 Pass - 3,138 0.03 0.99 0.07 0.03 0.99 0.07 0.0% 0.0% 0.0%

P Fail Pass 53 1.7% 0.10 1.64 0.31 0.04 1.23 0.08 54.8% 24.8% 74.6%

Fail Unresolv. 8 0.3% 0.14 3.70 0.57 0.05 1.22 0.19 67.0% 67.0% 67.0%

Fail Waiver 0 0.0% ------ - - -

Total Fail% 3,199 1.9% 0.03 1.00 0.07 0.03 0.99 0.07 3.9% 1.3% 6.6%

2012 Pass - 2,356 0.02 1.01 0.06 0.02 1.01 0.06 0.0% 0.0% 0.0%

P Fail Pass 29 1.2% 0.06 3.51 0.17 0.02 0.83 0.03 75.8% 76.4% 80.1%

Fail Unresolv. 4 0.2% 0.03 1.21 0.09 0.01 0.40 0.03 67.0% 67.0% 67.0%

Fail Waiver 0 0.0% ------ - - -

Total Fail% 2,389 1.4% 0.03 1.04 0.06 0.02 1.01 0.06 2.4% 3.3% 2.9%

2013 Pass - 633 0.02 0.75 0.06 0.02 0.75 0.06 0.0% 0.0% 0.0%

P Fail Pass 3 0.5% 0.01 0.71 0.23 0.02 0.24 0.01 -65.3% 65.8% 93.6%

Fail Unresolv. 4 0.6% 0.59 6.58 1.10 0.49 2.20 0.36 18.5% 66.5% 66.7%

Fail Waiver 0 0.0% ------ - - -

Total Fail% 640 1.1% 0.02 0.79 0.07 0.02 0.76 0.06 2.6% 3.7% 8.6%

2014 Pass - 21 0.03 0.85 0.06 0.03 0.85 0.06 0.0% 0.0% 0.0%

P Fail Pass 0 0.0% ------ - - -

Fail Unresolv. 0 0.0% ------ - - -

Fail Waiver 0 0.0% ------ - - -

Total Fail% 21 0.0% 0.03 0.85 0.06 0.03 0.85 0.06 0.0% 0.0% 0.0%

A1-4
Appendix A1 Colorado 2013 Transient Test Emissions Reductions

Unresolved fails remaining in area 33%

Model First Last Initial Final Reduction %

Year/Type Result Result Vehicles Fail% HC CO NOX HC CO NOX HC CO NOX

Total Passenger Vehicles

All Pass - 401,431 0.17 2.51 0.45 0.17 2.51 0.45 0.0% 0.0% 0.0%

P Fail Pass 27,026 6.2% 0.84 11.75 1.25 0.33 3.94 0.75 60.9% 66.5% 39.5%

Fail Unresolv. 5,249 1.2% 2.42 27.28 2.14 0.79 9.03 0.70 67.1% 66.9% 67.2%

Fail Waiver 220 0.1% 2.67 33.53 2.36 2.50 30.24 2.26 6.2% 9.8% 4.3%

Total Fail% 433,926 7.5% 0.24 3.40 0.52 0.19 2.69 0.47 21.5% 20.9% 9.3%

A1-5
Appendix A1 Colorado 2013 Transient Test Emissions Reductions

Unresolved fails remaining in area 33%

Model First Last Initial Final Reduction %

Year/Type Result Result Vehicles Fail% HC CO NOX HC CO NOX HC CO NOX

1982 Pass - 247 2.44 30.88 2.88 2.44 30.88 2.88 0.0% 0.0% 0.0%

T Fail Pass 103 25.9% 4.34 68.97 2.61 2.35 30.83 2.58 45.8% 55.3% 1.2%

Fail Unresolv. 46 11.6% 6.88 103.08 2.42 2.10 33.75 0.83 69.5% 67.3% 65.6%

Fail Waiver 1 0.3% 3.57 10.40 6.82 1.89 137.67 0.12 46.9% ####### 98.2%

Total Fail% 397 37.8% 3.45 49.08 2.76 2.38 31.47 2.56 31.1% 35.9% 7.6%

1983 Pass - 482 2.90 32.87 2.53 2.90 32.87 2.53 0.0% 0.0% 0.0%

T Fail Pass 165 22.9% 4.03 59.42 3.02 2.40 28.71 2.65 40.6% 51.7% 12.3%

Fail Unresolv. 71 9.9% 5.48 98.37 2.22 1.78 33.12 0.72 67.6% 66.3% 67.5%

Fail Waiver 1 0.1% 2.15 66.24 2.48 2.15 66.24 2.48 0.0% 0.0% 0.0%

Total Fail% 719 33.0% 3.41 45.48 2.61 2.67 31.99 2.38 21.7% 29.7% 8.9%

1984 Pass - 603 1.96 24.05 2.65 1.96 24.05 2.65 0.0% 0.0% 0.0%

T Fail Pass 240 24.9% 3.94 58.19 2.68 2.04 24.85 2.75 48.3% 57.3% -2.7%

Fail Unresolv. 116 12.0% 6.19 98.68 2.48 1.79 32.53 0.82 71.1% 67.0% 66.8%

Fail Waiver 6 0.6% 4.21 39.05 5.43 3.92 39.02 5.49 6.9% 0.1% -1.0%

Total Fail% 965 37.5% 2.98 41.60 2.65 1.97 25.36 2.47 33.7% 39.0% 6.8%

1985 Pass - 1,011 1.84 19.25 2.78 1.84 19.25 2.78 0.0% 0.0% 0.0%

T Fail Pass 322 21.7% 3.39 53.69 3.04 1.87 22.16 2.88 44.7% 58.7% 5.4%

Fail Unresolv. 144 9.7% 5.67 93.91 2.12 1.85 31.34 0.66 67.3% 66.6% 68.8%

Fail Waiver 4 0.3% 7.34 131.13 1.03 3.68 94.91 0.68 49.9% 27.6% 34.2%

Total Fail% 1,481 31.7% 2.56 34.30 2.77 1.85 21.27 2.59 27.7% 38.0% 6.4%

1986 Pass - 1,127 1.64 16.23 2.55 1.64 16.23 2.55 0.0% 0.0% 0.0%

T Fail Pass 355 21.8% 3.26 45.75 2.83 1.78 18.18 2.79 45.3% 60.3% 1.7%

Fail Unresolv. 136 8.4% 6.06 89.08 2.28 1.89 28.87 0.78 68.8% 67.6% 65.8%

Fail Waiver 7 0.4% 4.41 82.89 2.29 3.25 82.94 2.60 26.3% -0.1% -13.7%

Total Fail% 1,625 30.6% 2.37 29.07 2.59 1.70 18.01 2.45 28.5% 38.1% 5.2%

1987 Pass - 1,865 1.49 14.20 2.41 1.49 14.20 2.41 0.0% 0.0% 0.0%

T Fail Pass 405 16.8% 2.86 35.71 2.70 1.47 13.51 2.52 48.4% 62.2% 6.8%

Fail Unresolv. 138 5.7% 4.75 67.54 2.45 1.40 22.80 0.80 70.5% 66.2% 67.3%

Fail Waiver 8 0.3% 4.18 73.16 3.05 3.27 71.94 2.68 21.7% 1.7% 12.0%

Total Fail% 2,416 22.8% 1.92 21.05 2.46 1.49 14.77 2.33 22.2% 29.8% 5.1%

1988 Pass - 1,990 1.34 12.12 2.25 1.34 12.12 2.25 0.0% 0.0% 0.0%

T Fail Pass 429 16.7% 2.63 30.85 2.78 1.37 12.50 2.25 48.0% 59.5% 19.0%

Fail Unresolv. 144 5.6% 5.17 54.41 2.91 1.69 17.71 0.96 67.4% 67.4% 67.2%

Fail Waiver 5 0.2% 5.75 102.88 0.92 4.93 97.83 0.62 14.2% 4.9% 32.5%

Total Fail% 2,568 22.5% 1.78 17.79 2.38 1.37 12.66 2.18 23.0% 28.8% 8.4%

1989 Pass - 3,146 1.24 12.48 2.13 1.24 12.48 2.13 0.0% 0.0% 0.0%

T Fail Pass 610 15.4% 2.77 31.58 2.75 1.32 11.99 2.37 52.5% 62.0% 13.9%

Fail Unresolv. 186 4.7% 5.00 55.35 2.95 1.57 17.62 0.98 68.5% 68.2% 66.8%

Fail Waiver 11 0.3% 4.32 60.42 3.42 4.26 62.47 3.57 1.3% -3.4% -4.2%

Total Fail% 3,953 20.4% 1.66 17.58 2.27 1.27 12.79 2.12 23.2% 27.3% 6.7%

A1-6
Appendix A1 Colorado 2013 Transient Test Emissions Reductions

Unresolved fails remaining in area 33%

Model First Last Initial Final Reduction %

Year/Type Result Result Vehicles Fail% HC CO NOX HC CO NOX HC CO NOX

1990 Pass - 2,587 1.22 11.73 2.21 1.22 11.73 2.21 0.0% 0.0% 0.0%

T Fail Pass 561 17.0% 2.91 33.43 2.66 1.32 11.87 2.30 54.8% 64.5% 13.6%

Fail Unresolv. 137 4.2% 5.17 48.25 2.97 1.61 15.99 0.96 68.8% 66.9% 67.6%

Fail Waiver 9 0.3% 5.27 43.78 3.24 3.03 32.88 2.72 42.5% 24.9% 16.1%

Total Fail% 3,294 21.5% 1.68 17.03 2.32 1.26 11.99 2.17 25.3% 29.6% 6.3%

1991 Pass - 4,396 1.01 11.35 1.91 1.01 11.35 1.91 0.0% 0.0% 0.0%

T Fail Pass 771 14.4% 2.19 26.67 2.64 1.10 10.49 2.09 49.9% 60.7% 20.8%

Fail Unresolv. 168 3.1% 3.98 47.34 2.96 1.53 15.89 0.98 61.4% 66.4% 66.8%

Fail Waiver 8 0.1% 3.02 36.74 4.75 3.34 34.74 3.54 -10.4% 5.5% 25.5%

Total Fail% 5,343 17.7% 1.28 14.73 2.05 1.04 11.41 1.91 18.3% 22.6% 7.0%

1992 Pass - 3,999 1.04 11.07 1.95 1.04 11.07 1.95 0.0% 0.0% 0.0%

T Fail Pass 738 15.0% 2.32 24.54 2.63 1.15 11.10 2.12 50.5% 54.8% 19.4%

Fail Unresolv. 173 3.5% 4.78 45.77 3.00 1.38 14.67 0.98 71.1% 68.0% 67.3%

Fail Waiver 7 0.1% 3.38 36.17 2.06 4.50 45.47 1.92 -33.1% -25.7% 6.7%

Total Fail% 4,917 18.7% 1.37 14.35 2.09 1.08 11.25 1.94 21.5% 21.6% 7.1%

1993 Pass - 7,277 1.01 10.52 2.08 1.01 10.52 2.08 0.0% 0.0% 0.0%

T Fail Pass 1,108 12.8% 2.45 24.76 2.98 1.12 10.54 2.10 54.0% 57.4% 29.4%

Fail Unresolv. 249 2.9% 4.17 36.68 3.29 1.35 12.33 1.09 67.7% 66.4% 66.8%

Fail Waiver 13 0.2% 3.51 24.19 4.86 3.06 24.65 3.86 13.0% -1.9% 20.6%

Total Fail% 8,647 15.8% 1.29 13.12 2.23 1.04 10.60 2.05 19.5% 19.2% 7.9%

1994 Pass - 8,368 0.78 8.74 1.80 0.78 8.74 1.80 0.0% 0.0% 0.0%

T Fail Pass 1,494 14.6% 1.99 21.24 2.73 0.87 9.12 1.89 56.1% 57.1% 30.7%

Fail Unresolv. 376 3.7% 3.86 38.24 3.19 1.26 11.98 1.07 67.5% 68.7% 66.5%

Fail Waiver 14 0.1% 2.62 23.34 3.88 1.84 22.04 3.81 29.7% 5.6% 1.8%

Total Fail% 10,252 18.4% 1.07 11.66 1.99 0.81 8.93 1.79 24.2% 23.4% 10.1%

1995 Pass - 11,703 0.73 8.53 1.79 0.73 8.53 1.79 0.0% 0.0% 0.0%

T Fail Pass 1,987 14.0% 1.92 20.98 2.88 0.83 8.58 1.86 56.6% 59.1% 35.3%

Fail Unresolv. 501 3.5% 3.32 29.87 3.70 1.08 9.66 1.22 67.6% 67.7% 67.1%

Fail Waiver 29 0.2% 4.24 30.42 2.66 3.26 26.07 2.74 23.1% 14.3% -3.1%

Total Fail% 14,220 17.7% 1.00 11.07 2.01 0.76 8.61 1.78 23.4% 22.2% 11.4%

1996 Pass - 10,587 0.42 5.41 1.37 0.42 5.41 1.37 0.0% 0.0% 0.0%

T Fail Pass 1,576 12.6% 1.03 13.86 2.28 0.45 5.71 1.51 56.2% 58.8% 33.7%

Fail Unresolv. 292 2.3% 2.58 26.11 3.22 0.87 8.98 1.04 66.3% 65.6% 67.6%

Fail Waiver 15 0.1% 3.07 36.78 2.97 1.94 25.26 3.08 36.8% 31.3% -3.7%

Total Fail% 12,470 15.1% 0.55 7.00 1.53 0.44 5.56 1.38 20.7% 20.6% 9.7%

1997 Pass - 17,878 0.36 5.13 1.26 0.36 5.13 1.26 0.0% 0.0% 0.0%

T Fail Pass 2,593 12.4% 0.94 13.06 2.19 0.41 5.57 1.38 55.9% 57.4% 37.3%

Fail Unresolv. 434 2.1% 2.24 21.21 3.55 0.70 6.89 1.16 68.9% 67.5% 67.5%

Fail Waiver 22 0.1% 1.70 24.08 3.51 1.49 20.97 3.27 12.5% 12.9% 6.7%

Total Fail% 20,927 14.6% 0.48 6.47 1.42 0.38 5.24 1.27 20.5% 19.0% 10.6%

A1-7
Appendix A1 Colorado 2013 Transient Test Emissions Reductions

Unresolved fails remaining in area 33%

Model First Last Initial Final Reduction %

Year/Type Result Result Vehicles Fail% HC CO NOX HC CO NOX HC CO NOX

1998 Pass - 17,654 0.32 4.53 1.11 0.32 4.53 1.11 0.0% 0.0% 0.0%

T Fail Pass 2,432 11.8% 0.89 12.62 2.12 0.38 4.98 1.27 57.9% 60.5% 40.0%

Fail Unresolv. 461 2.2% 1.92 22.04 3.22 0.64 6.97 1.05 66.9% 68.4% 67.4%

Fail Waiver 18 0.1% 1.11 18.94 3.15 1.05 17.76 3.21 5.9% 6.2% -1.9%

Total Fail% 20,565 14.2% 0.42 5.90 1.28 0.33 4.65 1.13 21.2% 21.1% 11.7%

1999 Pass - 25,874 0.24 3.45 0.81 0.24 3.45 0.81 0.0% 0.0% 0.0%

T Fail Pass 3,088 10.5% 0.70 10.58 1.84 0.30 3.88 1.00 57.3% 63.3% 45.7%

Fail Unresolv. 527 1.8% 1.51 18.26 2.78 0.49 6.11 0.93 67.7% 66.6% 66.7%

Fail Waiver 28 0.1% 1.46 26.61 2.80 0.87 11.94 2.80 40.0% 55.1% 0.1%

Total Fail% 29,517 12.3% 0.31 4.48 0.95 0.25 3.55 0.83 19.8% 20.8% 12.8%

2000 Pass - 22,666 0.21 3.04 0.70 0.21 3.04 0.70 0.0% 0.0% 0.0%

T Fail Pass 2,390 9.4% 0.58 9.64 1.54 0.26 3.72 0.89 54.7% 61.4% 42.1%

Fail Unresolv. 322 1.3% 1.99 23.04 2.63 0.59 8.00 0.87 70.0% 65.3% 66.8%

Fail Waiver 15 0.1% 1.14 17.08 3.48 1.56 17.63 3.24 -37.0% -3.2% 7.0%

Total Fail% 25,393 10.7% 0.27 3.93 0.80 0.22 3.18 0.72 17.7% 19.1% 10.4%

2001 Pass - 29,019 0.14 2.61 0.47 0.14 2.61 0.47 0.0% 0.0% 0.0%

T Fail Pass 2,370 7.5% 0.42 8.31 1.14 0.19 3.20 0.63 54.8% 61.5% 45.0%

Fail Unresolv. 182 0.6% 1.93 21.89 2.85 0.67 8.34 0.91 65.4% 61.9% 68.1%

Fail Waiver 13 0.0% 0.94 15.88 3.35 1.39 11.77 3.72 -47.5% 25.9% -11.2%

Total Fail% 31,584 8.1% 0.17 3.16 0.54 0.15 2.69 0.49 14.2% 14.7% 9.2%

2002 Pass - 23,316 0.11 2.81 0.42 0.11 2.81 0.42 0.0% 0.0% 0.0%

T Fail Pass 1,740 6.9% 0.39 9.38 1.10 0.17 3.13 0.60 56.0% 66.7% 45.2%

Fail Unresolv. 163 0.6% 1.53 26.31 2.57 0.52 8.64 0.83 66.2% 67.2% 67.7%

Fail Waiver 15 0.1% 0.95 15.60 2.86 0.90 14.11 2.61 5.9% 9.5% 8.7%

Total Fail% 25,234 7.6% 0.14 3.43 0.48 0.12 2.88 0.44 15.1% 15.9% 9.5%

2003 Pass - 31,096 0.09 1.66 0.31 0.09 1.66 0.31 0.0% 0.0% 0.0%

T Fail Pass 1,774 5.4% 0.34 7.40 0.77 0.13 2.60 0.43 61.6% 64.8% 43.8%

Fail Unresolv. 89 0.3% 2.02 24.68 2.44 0.59 8.21 0.82 70.7% 66.7% 66.3%

Fail Waiver 5 0.0% 2.36 60.00 2.74 1.63 28.55 4.12 30.8% 52.4% -50.4%

Total Fail% 32,964 5.7% 0.11 2.04 0.34 0.09 1.73 0.32 14.2% 15.1% 6.5%

2004 Pass - 23,967 0.06 1.42 0.18 0.06 1.42 0.18 0.0% 0.0% 0.0%

T Fail Pass 1,378 5.4% 0.28 6.45 0.63 0.11 2.43 0.28 62.6% 62.3% 54.7%

Fail Unresolv. 71 0.3% 0.84 15.58 2.56 0.28 5.19 0.84 66.3% 66.7% 67.0%

Fail Waiver 1 0.0% 0.02 0.33 2.74 0.01 0.77 2.05 28.9% -131.1% 25.0%

Total Fail% 25,417 5.7% 0.08 1.73 0.21 0.07 1.48 0.19 14.3% 14.3% 11.0%

2005 Pass - 35,394 0.05 1.06 0.12 0.05 1.06 0.12 0.0% 0.0% 0.0%

T Fail Pass 1,266 3.4% 0.21 3.70 0.46 0.09 1.85 0.21 59.5% 49.9% 54.8%

Fail Unresolv. 48 0.1% 0.80 11.81 1.90 0.27 3.80 0.66 66.4% 67.8% 65.4%

Fail Waiver 7 0.0% 0.81 10.55 2.79 0.73 18.26 2.54 10.0% -73.0% 9.1%

Total Fail% 36,715 3.6% 0.06 1.17 0.14 0.06 1.10 0.13 8.3% 6.2% 7.6%

A1-8
Appendix A1 Colorado 2013 Transient Test Emissions Reductions

Unresolved fails remaining in area 33%

Model First Last Initial Final Reduction %

Year/Type Result Result Vehicles Fail% HC CO NOX HC CO NOX HC CO NOX

2006 Pass - 23,116 0.04 1.03 0.11 0.04 1.03 0.11 0.0% 0.0% 0.0%

T Fail Pass 935 3.9% 0.15 2.78 0.53 0.07 1.39 0.18 52.9% 49.9% 66.6%

Fail Unresolv. 32 0.1% 1.01 20.90 2.94 0.38 7.25 1.00 62.7% 65.3% 65.9%

Fail Waiver 0 0.0% ------ - - -

Total Fail% 24,083 4.0% 0.05 1.12 0.13 0.05 1.05 0.11 7.8% 6.4% 12.6%

2007 Pass - 35,304 0.03 0.85 0.09 0.03 0.85 0.09 0.0% 0.0% 0.0%

T Fail Pass 1,272 3.5% 0.09 2.37 0.26 0.04 1.36 0.11 55.4% 42.7% 59.9%

Fail Unresolv. 10 0.0% 0.59 7.81 2.75 0.20 2.58 0.91 67.0% 67.0% 67.0%

Fail Waiver 0 0.0% ------ - - -

Total Fail% 36,586 3.5% 0.04 0.91 0.10 0.03 0.87 0.09 5.4% 4.0% 6.2%

2008 Pass - 18,094 0.03 0.90 0.09 0.03 0.90 0.09 0.0% 0.0% 0.0%

T Fail Pass 745 4.0% 0.09 2.41 0.20 0.04 1.65 0.08 51.4% 31.6% 60.2%

Fail Unresolv. 12 0.1% 0.38 15.52 0.96 0.13 5.21 0.33 65.3% 66.4% 65.9%

Fail Waiver 0 0.0% ------ - - -

Total Fail% 18,851 4.0% 0.03 0.97 0.09 0.03 0.93 0.08 5.9% 3.8% 5.8%

2009 Pass - 23,024 0.03 0.82 0.08 0.03 0.82 0.08 0.0% 0.0% 0.0%

T Fail Pass 655 2.8% 0.03 1.08 0.15 0.03 1.12 0.06 12.7% -3.8% 60.9%

Fail Unresolv. 6 0.0% 0.56 4.79 0.84 0.18 1.58 0.28 67.0% 67.0% 67.0%

Fail Waiver 0 0.0% ------ - - -

Total Fail% 23,685 2.8% 0.03 0.83 0.08 0.03 0.83 0.07 0.7% 0.0% 3.4%

2010 Pass - 6,327 0.03 0.77 0.07 0.03 0.77 0.07 0.0% 0.0% 0.0%

T Fail Pass 147 2.3% 0.06 2.25 0.07 0.02 0.95 0.05 59.7% 57.9% 21.3%

Fail Unresolv. 4 0.1% 0.56 6.18 1.61 0.19 2.04 0.53 67.0% 67.0% 67.0%

Fail Waiver 0 0.0% ------ - - -

Total Fail% 6,478 2.3% 0.03 0.81 0.07 0.03 0.78 0.07 3.6% 4.0% 1.5%

2011 Pass - 2,239 0.03 0.84 0.06 0.03 0.84 0.06 0.0% 0.0% 0.0%

T Fail Pass 54 2.3% 0.04 1.82 0.17 0.02 1.16 0.08 33.8% 36.1% 53.0%

Fail Unresolv. 5 0.2% 0.06 2.30 0.20 0.02 0.76 0.07 67.0% 67.0% 67.0%

Fail Waiver 0 0.0% ------ - - -

Total Fail% 2,298 2.6% 0.03 0.86 0.06 0.03 0.85 0.06 1.3% 2.2% 4.0%

2012 Pass - 1,302 0.03 0.77 0.05 0.03 0.77 0.05 0.0% 0.0% 0.0%

T Fail Pass 13 1.0% 0.04 0.74 0.06 0.02 0.63 0.06 53.0% 14.8% -9.8%

Fail Unresolv. 0 0.0% ------ - - -

Fail Waiver 0 0.0% ------ - - -

Total Fail% 1,315 1.0% 0.03 0.77 0.05 0.03 0.77 0.05 0.7% 0.1% -0.1%

2013 Pass - 594 0.03 0.70 0.05 0.03 0.70 0.05 0.0% 0.0% 0.0%

T Fail Pass 3 0.5% 0.02 0.65 0.04 0.01 0.71 0.02 65.5% -9.4% 42.8%

Fail Unresolv. 1 0.2% 0.47 8.07 2.35 0.16 2.66 0.78 67.0% 67.0% 67.0%

Fail Waiver 0 0.0% ------ - - -

Total Fail% 598 0.7% 0.03 0.72 0.05 0.03 0.71 0.05 2.0% 1.2% 5.1%

2014 Pass - 30 0.02 0.52 0.05 0.02 0.52 0.05 0.0% 0.0% 0.0%

T Fail Pass 0 0.0% ------ - - -

Fail Unresolv. 0 0.0% ------ - - -

Fail Waiver 0 0.0% ------ - - -

Total Fail% 30 0.0% 0.02 0.52 0.05 0.02 0.52 0.05 0.0% 0.0% 0.0%

A1-9
Appendix A1 Colorado 2013 Transient Test Emissions Reductions

Unresolved fails remaining in area 33%

Model First Last Initial Final Reduction %

Year/Type Result Result Vehicles Fail% HC CO NOX HC CO NOX HC CO NOX

Total Trucks

All Pass - 396,282 0.24 3.25 0.61 0.24 3.25 0.61 0.0% 0.0% 0.0%

T Fail Pass 33,719 7.7% 1.06 14.33 1.73 0.49 5.81 1.15 53.6% 59.5% 33.6%

Fail Unresolv. 5,244 1.2% 3.19 37.07 2.98 1.02 12.22 0.98 68.0% 67.0% 67.1%

Fail Waiver 262 0.1% 2.70 33.90 3.19 2.22 29.85 3.06 17.7% 11.9% 4.3%

Total Fail% 435,507 9.0% 0.34 4.54 0.73 0.27 3.57 0.66 20.8% 21.2% 9.5%

Fleet Total

All Pass - 797,713 0.20 2.88 0.53 0.20 2.88 0.53 0.0% 0.0% 0.0%

All Fail Pass 60,745 7.0% 0.96 13.18 1.51 0.42 4.98 0.97 56.4% 62.2% 35.8%

Fail Unresolv. 10,493 1.2% 2.80 32.17 2.56 0.91 10.62 0.84 67.6% 67.0% 67.1%

Fail Waiver 482 0.1% 2.68 33.74 2.81 2.35 30.03 2.69 12.5% 11.0% 4.3%

Total Fail% 869,433 8.2% 0.29 3.97 0.62 0.23 3.13 0.56 21.1% 21.1% 9.4%

A1-10
Appendix B Colorado 2013

Enhanced IM240 Test Reduction Tons

Initial Tons/Yr Final Tons/Yr Reduction Tons/Yr

Type

 Annual 

Miles 

 Unique 

Vehicles HC CO NOx HC CO NOx HC CO NOx

P 1982 4,304 344 4.0 48.6 3.3 2.7 32.8 3.1 1.3 15.8 0.2

P 1983 4,304 612 5.0 62.9 5.9 3.8 41.5 5.5 1.2 21.3 0.4

P 1984 4,304 851 7.8 92.5 7.7 5.4 55.3 7.3 2.4 37.2 0.4

P 1985 4,304 1,428 9.8 119.6 13.0 7.4 77.0 12.2 2.4 42.5 0.8

P 1986 4,434 1,520 10.0 102.3 13.9 7.4 65.9 13.0 2.6 36.3 0.9

P 1987 4,481 2,350 13.5 139.0 21.5 10.4 98.6 20.3 3.1 40.4 1.2

P 1988 4,502 2,160 12.2 124.2 17.7 8.6 88.0 16.8 3.7 36.2 0.9

P 1989 4,552 3,748 18.5 207.4 31.1 14.3 156.3 29.7 4.3 51.1 1.4

P 1990 4,780 4,600 22.8 260.1 41.2 17.8 193.4 38.5 4.9 66.7 2.7

P 1991 5,088 7,129 33.1 386.7 61.9 25.0 280.8 57.4 8.1 105.8 4.5

P 1992 5,430 6,873 33.6 389.7 61.4 25.0 271.4 57.8 8.6 118.4 3.6

P 1993 5,672 9,830 43.4 491.5 93.9 35.3 368.6 88.1 8.0 122.8 5.8

P 1994 6,002 10,446 42.2 489.4 85.9 31.4 367.2 79.8 10.8 122.2 6.1

P 1995 6,331 16,049 59.0 690.4 122.8 46.8 540.1 113.9 12.2 150.3 8.9

P 1996 6,653 14,405 44.0 540.2 95.5 34.8 420.3 87.5 9.2 119.9 8.0

P 1997 6,974 21,237 60.3 798.6 132.9 50.5 642.5 123.6 9.8 156.1 9.3

P 1998 7,369 20,164 49.9 740.5 115.1 39.5 577.3 104.3 10.4 163.2 10.8

P 1999 7,764 27,684 59.7 890.6 154.1 48.8 722.4 138.0 10.8 168.2 16.1

P 2000 8,188 26,739 49.4 790.6 132.4 38.7 633.4 113.6 10.8 157.2 18.9

P 2001 8,613 32,185 42.7 769.7 112.5 33.3 653.9 97.7 9.4 115.8 14.8

P 2002 9,032 27,050 32.7 758.8 87.3 25.5 655.6 74.8 7.2 103.2 12.5

P 2003 9,450 32,456 26.1 534.8 82.8 21.0 470.0 72.9 5.1 64.8 10.0

P 2004 9,905 21,710 17.1 366.5 45.1 13.4 312.0 37.9 3.7 54.5 7.2

P 2005 10,360 32,217 17.6 411.3 53.5 14.4 359.6 46.5 3.2 51.7 7.0

P 2006 10,746 22,687 13.1 345.9 36.1 10.6 306.3 28.4 2.5 39.6 7.7

P 2007 11,132 31,780 13.3 380.1 41.0 12.2 364.3 35.2 1.1 15.8 5.8

P 2008 11,870 16,188 8.2 229.5 23.4 7.0 215.1 18.3 1.3 14.3 5.0

P 2009 12,023 27,165 11.4 353.5 33.7 10.5 345.0 29.3 0.8 8.5 4.4

P 2010 12,307 6,070 2.5 83.1 6.9 2.3 79.6 6.1 0.3 3.6 0.8

P 2011 12,357 3,199 1.2 43.7 3.2 1.2 43.2 3.0 0.0 0.6 0.2

P 2012 11,600 2,389 0.8 31.7 1.8 0.7 30.7 1.8 0.0 1.0 0.1

P 2013 9,650 640 0.2 5.4 0.4 0.2 5.2 0.4 0.0 0.2 0.0

P Total 433,905 765.1 11678.8 1739.0 605.8 9473.3 1562.7 159.3 2205.5 176.3

T 1982 4,550 397 6.9 97.7 5.5 4.7 62.7 5.1 2.1 35.1 0.4

T 1983 4,550 719 12.3 164.0 9.4 9.6 115.4 8.6 2.7 48.6 0.8

T 1984 4,554 965 14.4 201.5 12.8 9.6 122.8 12.0 4.9 78.7 0.9

T 1985 4,562 1,481 19.1 255.5 20.6 13.8 158.4 19.3 5.3 97.1 1.3

T 1986 4,583 1,625 19.5 238.6 21.2 13.9 147.8 20.1 5.6 90.8 1.1

T 1987 4,630 2,416 23.6 259.6 30.3 18.4 182.1 28.8 5.3 77.5 1.6

T 1988 4,668 2,568 23.5 235.1 31.4 18.1 167.3 28.8 5.4 67.8 2.6

T 1989 4,741 3,953 34.3 363.2 46.9 26.3 264.2 43.8 8.0 99.0 3.1

T 1990 4,851 3,294 29.6 300.0 40.9 22.1 211.2 38.3 7.5 88.8 2.6

T 1991 5,019 5,343 37.8 435.5 60.7 30.8 337.2 56.5 6.9 98.3 4.2

T 1992 5,256 4,917 39.0 408.8 59.6 30.6 320.5 55.4 8.4 88.3 4.2

T 1993 5,519 8,647 67.8 690.1 117.4 54.6 557.4 108.0 13.2 132.7 9.3

T 1994 5,824 10,252 70.6 767.4 130.7 53.6 587.7 117.6 17.1 179.7 13.2

T 1995 6,135 14,220 95.7 1064.3 193.3 73.3 828.3 171.3 22.4 236.0 22.0

T 1996 6,471 12,470 49.3 622.9 136.0 39.1 494.3 122.8 10.2 128.5 13.2

T 1997 6,940 20,927 76.1 1035.3 227.8 60.6 838.6 203.5 15.6 196.7 24.2

T 1998 7,437 20,565 71.5 993.9 215.3 56.4 784.5 190.2 15.2 209.4 25.1

T 1999 7,863 29,517 78.8 1146.5 243.4 63.2 908.0 212.4 15.6 238.5 31.1

T 2000 8,345 25,393 62.4 916.9 187.8 51.3 742.2 168.3 11.0 174.7 19.5

T 2001 8,900 31,584 53.4 977.7 166.7 45.8 834.2 151.3 7.6 143.6 15.4

T 2002 9,502 25,234 37.9 905.6 127.3 32.2 761.2 115.2 5.7 144.4 12.1

T 2003 10,087 32,964 39.3 747.8 124.8 33.7 635.1 116.6 5.6 112.7 8.2

T 2004 10,727 25,417 23.2 520.0 63.9 19.9 445.8 56.9 3.3 74.2 7.0

T 2005 11,245 36,715 27.6 531.7 62.7 25.3 498.6 57.9 2.3 33.1 4.7

T 2006 11,817 24,083 15.4 352.6 40.5 14.2 330.1 35.4 1.2 22.6 5.1

T 2007 12,303 36,586 17.8 450.0 47.4 16.8 431.8 44.4 1.0 18.2 3.0

T 2008 12,834 18,851 9.2 258.9 24.1 8.6 249.1 22.7 0.5 9.8 1.4

T 2009 13,215 23,685 9.7 286.7 26.8 9.6 286.8 25.9 0.1 -0.1 0.9

T 2010 13,433 6,478 2.7 77.5 6.6 2.6 74.4 6.5 0.1 3.1 0.1

T 2011 13,514 2,298 1.0 29.6 2.0 1.0 28.9 2.0 0.0 0.6 0.1

T 2012 12,428 1,315 0.5 13.8 1.0 0.5 13.8 1.0 0.0 0.0 0.0

T 2013 8,995 598 0.2 4.2 0.3 0.2 4.2 0.3 0.0 0.1 0.0

T Total 435,477 1070.3 15352.9 2485.0 860.7 12424.6 2246.6 209.6 2928.4 238.4

Total 869,382 1835.4 27031.8 4224.0 1466.5 21897.9 3809.3 368.9 5133.9 414.8

B-1
20% 19%

Appendix B - Colorado 2011

RapidScreen Audit IM240 Test Reduction Tons

Initial Tons/Yr Final Tons/Yr Reduction Tons/Yr

Type

 Annual 

Miles 

 Unique 

Vehicles HC CO NOx HC CO NOx HC CO NOx

P 1982 4,304 - 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

P 1983 4,304 - 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

P 1984 4,304 - 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

P 1985 4,304 1 0.0 0.1 0.0 0.0 0.1 0.0 0.0 0.0 0.0

P 1986 4,434 2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

P 1987 4,481 2 0.0 0.1 0.0 0.0 0.1 0.0 0.0 0.0 0.0

P 1988 4,502 - 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

P 1989 4,552 4 0.0 0.1 0.0 0.0 0.1 0.0 0.0 0.0 0.0

P 1990 4,780 2 0.0 0.1 0.0 0.0 0.1 0.0 0.0 0.0 0.0

P 1991 5,088 4 0.0 0.1 0.0 0.0 0.1 0.0 0.0 0.0 0.0

P 1992 5,430 6 0.0 0.2 0.0 0.0 0.2 0.0 0.0 0.0 0.0

P 1993 5,672 5 0.0 0.1 0.0 0.0 0.1 0.0 0.0 0.0 0.0

P 1994 6,002 9 0.0 0.3 0.1 0.0 0.3 0.1 0.0 0.0 0.0

P 1995 6,331 27 0.1 0.7 0.2 0.1 0.7 0.2 0.0 0.0 0.0

P 1996 6,653 21 0.0 0.6 0.1 0.0 0.6 0.1 0.0 0.0 0.0

P 1997 6,974 54 0.1 1.3 0.3 0.1 1.3 0.3 0.0 0.0 0.0

P 1998 7,369 49 0.1 1.8 0.3 0.1 1.3 0.2 0.0 0.5 0.0

P 1999 7,764 80 0.2 2.1 0.4 0.2 2.1 0.4 0.0 0.1 0.0

P 2000 8,188 76 0.1 1.6 0.3 0.1 1.6 0.3 0.0 0.0 0.0

P 2001 8,613 141 0.1 2.6 0.4 0.1 2.6 0.4 0.0 0.0 0.0

P 2002 9,032 132 0.1 4.4 0.4 0.1 3.0 0.4 0.0 1.4 0.0

P 2003 9,450 206 0.1 3.0 0.5 0.1 3.0 0.5 0.0 0.0 0.0

P 2004 9,905 114 0.1 1.5 0.2 0.1 1.5 0.2 0.0 0.0 0.0

P 2005 10,360 246 0.1 2.6 0.3 0.1 2.5 0.3 0.0 0.2 0.0

P 2006 10,746 127 0.0 1.4 0.1 0.0 1.4 0.1 0.0 0.0 0.0

P 2007 11,132 278 0.1 3.1 0.3 0.1 3.1 0.3 0.0 0.0 0.0

P 2008 11,870 61 0.0 0.7 0.1 0.0 0.7 0.1 0.0 0.0 0.0

P 2009 12,023 152 0.1 1.9 0.2 0.1 1.8 0.2 0.0 0.0 0.0

P 2010 12,307 - 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

P Total 1,799 1.5 30.4 4.1 1.4 28.3 4.1 0.1 2.1 0.0

T 1982 4,550 - 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

T 1983 4,550 - 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

T 1984 4,554 - 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

T 1985 4,562 - 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

T 1986 4,583 - 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

T 1987 4,630 1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

T 1988 4,668 - 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

T 1989 4,741 3 0.0 0.2 0.0 0.0 0.2 0.0 0.0 0.0 0.0

T 1990 4,851 1 0.0 0.1 0.0 0.0 0.1 0.0 0.0 0.0 0.0

T 1991 5,019 2 0.0 0.2 0.0 0.0 0.2 0.0 0.0 0.0 0.0

T 1992 5,256 4 0.0 0.3 0.0 0.0 0.3 0.0 0.0 0.0 0.0

T 1993 5,519 3 0.0 0.2 0.0 0.0 0.2 0.0 0.0 0.0 0.0

T 1994 5,824 4 0.0 0.3 0.0 0.0 0.2 0.0 0.0 0.1 0.0

T 1995 6,135 5 0.0 0.3 0.0 0.0 0.3 0.0 0.0 0.0 0.0

T 1996 6,471 19 0.1 1.1 0.1 0.1 0.8 0.1 0.0 0.3 0.0

T 1997 6,940 39 0.1 1.7 0.4 0.1 1.6 0.4 0.0 0.0 0.1

T 1998 7,437 59 0.2 2.1 0.5 0.2 2.0 0.5 0.0 0.1 0.0

T 1999 7,863 101 0.2 3.0 0.7 0.2 2.7 0.6 0.0 0.3 0.0

T 2000 8,345 86 0.1 2.0 0.5 0.1 2.0 0.5 0.0 0.0 0.0

T 2001 8,900 195 0.3 4.5 0.9 0.3 4.4 0.9 0.0 0.1 0.0

T 2002 9,502 135 0.2 3.9 0.6 0.1 3.1 0.6 0.0 0.7 0.0

T 2003 10,087 270 0.2 4.8 0.9 0.2 4.7 0.9 0.0 0.1 0.0

T 2004 10,727 181 0.1 2.7 0.4 0.1 2.8 0.4 0.0 -0.2 0.0

T 2005 11,245 419 0.3 6.0 0.7 0.3 5.8 0.7 0.0 0.2 0.0

T 2006 11,817 192 0.1 2.5 0.2 0.1 2.5 0.2 0.0 0.0 0.0

T 2007 12,303 459 0.2 5.7 0.6 0.2 5.1 0.6 0.0 0.6 0.0

T 2008 12,834 78 0.0 0.9 0.1 0.0 1.0 0.1 0.0 0.0 0.0

T 2009 13,215 179 0.1 2.3 0.2 0.1 2.4 0.2 0.0 0.0 0.0

T 2010 13,433 - 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

T Total 2,435 2.3 44.7 7.2 2.2 42.4 7.1 0.1 2.2 0.2

Total 4,234 3.8 75.1 11.3 3.6 70.8 11.2 0.1 4.3 0.2

B-2