A new Massachusetts truck and bus exhaust smoke testing program, which began Feb. 2, has drawn support and praise from Washington, DC–based Diesel Technology Forum, according to executive director Allen Schaeffer, who called the new regulation “a proven method to help improve air quality within the region.” The regulations require that diesel trucks and buses undergo an annual smoke emissions inspection in conjunction with their commercial vehicle safety checks. Excessive smoke is the exception, not the rule. It means there is a problem with the operation of the diesel engine  it is out of tune, needs maintenance, and is not operating efficiently  all of which are no good for the operator. Smoke represents unburned fuel. Smoke testing programs are cost-effective solutions that are good for the environment, for regulators, for truck and bus operators, and the public. Massachusetts will join 12 other states, which currently have programs to control excessive exhaust smoke. States adopting these programs can receive air quality credits toward meeting their clean air goals. Endorsed by the federal Environmental Protection Agency, the smoke testing programs have received encouragement and support from the Diesel Technology Forum.