A growing body of evidence indicates that one of the reasons for a rapidly growing discrepancy between official and real-world fuel consumption and emission values of new passenger cars is shortcomings in the certification testing schemes new vehicles and in the compliance protocols.
Vehicle manufacturers are increasingly able to exploit tolerances and flexibilities, leading to downward-trending type-approval emission levels that are not matched by a similar decrease in real-world emission levels—indeed, the real-world values contradict the type-approval results.
The recently uncovered use of an illegal defeat device by Volkswagen crosses a line between illegality and the simple exploitation of legal loopholes that allow manufacturers to observe the letter of a regulation while disregarding its spirit and intent.
But it nevertheless serves to dramatically highlight a broader underlying problem with today’s vehicle emissions testing and compliance systems.
A program designed to periodically check vehicle emissions to ensure they are within limits. Often referred to as an I/M (Inspection/Maintenance) program, they are used in numerous states and areas as required by the Environmental Protection Agency to improve air quality in those areas. Although the requirement comes from the federal government, states and their associated agencies have some flexibility in the type of test used, vehicle populations to be tested and other program-specific details.
Some states run centralized programs that have state-contracted test stations exclusively dedicated to testing. Other states run decentralized programs, where emissions can be tested at local repair facilities. In a few cases, states may run “hybrid” programs using both centralized and decentralized test stations.
The latest trend is to incorporate the use of second-generation onboard diagnostics (OBDII) into these programs, in many cases altogether eliminating the need for tailpipe emissions tests.