International Experience and Best Practices - Clean Air Initiative

prudent judgment on what level of standards will command political support. 140 The
pollutants covered will vary for gas vs. diesel engines (CO/HC/NOx vs. PM/smoke/
NOx). A very tough standard that many vehicles flunk could erode support, as could
a very easy standard that made the I/M program appear ineffectual. When phasing-in
standards, policymakers should set standards or “cut-points” be set so that 15 to 20
percent of vehicles fail. 141 However, this rate could be higher or lower depending on
technical and cost factors. A consultant study for Sri Lanka provides a good example of
how analysis and judgment can inform the recommendation of a set of standards (see
Box 3-5).
As emission standards for new vehicles are tightened, policymakers should set I/M
standards for these vehicles that are appropriately stringent, reflecting newer technology
and improved emissions performance. Older vehicles emit more due to the nature of
their technology, as well as the inevitable deterioration of age. While this should lead to
relatively lenient standards for older vehicles, at the same time, policymakers may want
to set a relatively tough standard for older high-emitting vehicles in order to create some
pressure for retiring the vehicle rather than maintaining it. 142
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BOX 3-4. HEAVY-DUTY DIESEL I/M PROGRAMS IN THE U.S.
Heavy-duty diesel vehicle emission inspection programs have been initiated in a number of
locations in the U.S. in the last decade in an effort to identify, test and repair vehicles that
emit excessive smoke. The earliest of these programs dates back to 1974 for the Arizona
program, but most programs were initiated in the mid to late 1990s. At present, there are 16
programs in operation in the U.S., and two in Canada. All of the 18 programs in operation
as of March 2004 measure smoke opacity only as a surrogate for diesel emissions, but
program structures and test methods vary across states.
At present, there are three specific types of programs used:
• Roadside Inspections: A sample of all trucks is selected at varied locations for
smoke opacity testing.
• Periodic Inspections: Trucks registered in a specific area are inspected annually or
biennially at an inspection facility.
• Self-Certification Program: This program is for fleets, which are allowed to conduct
periodic tests in their own maintenance facility and report the results to the state.
Most states use a test approved by the Society of Automotive Engineers for identifying a
diesel vehicle's smoke emissions, called the SAE J1667 "snap-acceleration" test, with pass/
fail standards of 55 percent smoke opacity for pre-1991 vehicles and 40 percent for 1991
and later vehicles.” (Author’s note: some states add a third category of pre-1974 or pre-1976
trucks with a 70 percent opacity standard)
Source: Diesel Technology Forum, Smoke Testing Programs
140 Faiz, A. et al, op. cit., pp. 141-144. Asian Development Bank, 2003, op. cit., p. 13-14. Weaver, C. and L.
Chan, op. cit., p. 41-42. One reviewer argued that current EU I/M standards represent “internationally
recognized” cut-points, but this was a lone viewpoint.
141 Asian Development Bank, 2003, op. cit., p. 14.
142 One reviewer argued strongly that technology alone should determine cut-points, and that age should
not be a factor.