Data were obtained on exhaust emissions at idle from four fleets of cars to develop information that would be needed for servicing vehicles rejected by state and city emission surveillance programs. As expected, emissions increased with car age. Pre-1968 European cars produced higher emissions and responded less favorably to tune-up than other pre-1968 cars. Idle emission standards already proposed can bring about rejection rates ranging from 10 to 60% of all cars depending on the emission standard and local car population. Extended idling can increase these rejection rates by 3 to 31% of all cars. Although most rejected cars passed emission standards after tune-up, a significant percentage required additional repair work in order to pass. It is clear that with several standards, some cars could not be made to pass at a reasonable cost.
Evaluation of exhaust analyzers has led to development of criteria for service station equipment. Analyzers have been manufactured that could meet these criteria.