I/M 240 is an "enhanced" inspection/maintenance vehicle emissions testing program for improving air quality in areas that fail to meet the federal government's ambient air quality standards. The test is similar to the Federal Test Procedure (FTP) that auto makers use to certify new vehicle emissions.

A key feature of the I/M 240 test procedure is the use of a special inertia dynamometer to simulate vehicle loads at various speeds during a 240-second drive cycle that includes acceleration, deceleration and cruise modes. The test can catch emission problems that often escape notice during a simple idle emissions test, but it requires a trained operator to "drive" the vehicle while it is on the dyno, and the special dyno that is required is very expensive. A single I/M 240 test lane can cost upwards of $150,000 or more!