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RSD Colorado

Colorado Remote Sensing

Remote Sensing Device (RSD) technology has deep roots in Colorado. Not only was remote sensing invented by Dr. Donald Stedman at Denver University in the late 80s, but most early studies that led to remote sensing's recognition and acceptance as an on-road screening supplement to traditional station-based I/M programs were conducted in Colorado.

Colorado's Greeley Pilot Study (1997)

Through a combined effort, remote sensing began in the mid-1990s to satisfy the Clean Air Act's requirement to test 0.5% of the I/M area fleet each year using an on-road measurement technique. The annual Denver 0.5% RSD campaign generated considerable interest in on-road screening within the Colorado Department of Health and Environment (CDPHE).

The Greeley on-road data was collected using a single AccuScanâ„¢ Model RSD-2000. Over a year and a half, nearly 600 vehicles were measured multiple times with RSD and immediately followed up with IM240 tests. The data provided a measure of the potential for remote sensing to identify both clean and high emitting vehicles on the road.
This landmark study is published on the U.S. EPA website ( The Greeley study served as the basis for not only the U.S. EPA's clean screen guidance document that emerged in early 1999, but also Colorado's clean screen program, which was launched in October 2003. Within a year of the guidance release in early 1999, Missouri launched the first clean screen program of its kind in April 2000. Based on the Greeley study, the U.S. EPA's FACA committee established that up to 50% of the clean vehicles in a registered area could be identified and exempted from their next scheduled I/M test with minimal loss of excess repairable emissions.

Colorado's Total Screening Program (2003 - present)

Colorado's Bill HB06-1302, which passed in May 2006, called for:
-The growth of remote sensing clean screening as cleaner new cars stay cleaner longer.
-The addition of high emitter identification to address the fewer high emitters today that represent a growing majority of the excess repairable emissions from light duty motor vehicle fleet.
-The continuous survey of on-road vehicle emission to track inventories and evaluate the I/M program's performance.

Colorado's RSD program began with three RSD4000s and a focus on clean screening in October, 2003. By July 2008, Colorado's total screen program was operating 18 RSD4600s around the Denver and North Front Range areas, was clean screening over 30% of its inspected vehicle population and was expanding high emitter identification which had started in late 2007. Colorado's clean screening and high emitter identification, in combination with I/M program evaluation is not only the largest RSD program in the world, collecting over 10M RSD measurements each year, but the most comprehensive (clean, high emitter and general monitoring), hence known as a "total screening" program. Under HB1302, Colorado plans to have RSD serve as the basis of tailpipe inspection in the future, requiring vehicles new and old, OBD-equipped or not, submit to a tailpipe test should their drive-by RSD reading indicate probable cause. At the same time, clean running vehicles can continue to demonstrate their compliance and earn exemption from more rigorous inspection, while the RSD-based general fleet emissions profiles dictate changes that may be required to the I/M program proceeding.

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May 2010 article/video on "Remote Sensing Could Exempt Cars From Emissions Test"


2009 Clean Air Conference Presentation: "Pre-screening and Evaluation of High Evaporative Emissions using RSD"(PDF 685 KB)by Jim Sidebottom, Colorado Department of Public Health and Environment

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