Abstract:

The purpose of an inspection and maintenance (I/M) program is to identify high-emitting vehicles and mitigate their impact on air quality and climate. I/M programs require vehicle owners to regularly subject their vehicles to a certified emissions test. Vehicles that fail the test, due to either emissions that exceed the regulatory threshold or to emissions control component malfunctions, are required to undergo repairs. High emitters typically make up a small percentage of a vehicle fleet, but are responsible for an inordinately large amount of total emissions. This paper, reviews the best practices for I/M programs, evaluate existing I/M testing methods and protocols and their limitations, examine new and emerging techniques for I/M testing, evaluate a range of I/M programs across the globe, and make recommendations about how to improve I/M programs in the future. Combined with other measures, such as remote sensing programs, cities can concentrate resources to monitor and improve the vehicle fleet with highest noncompliance ratios and therefore increase the compliance and pass rate of I/M testing.