Periodic Motor Vehicle Inspection as a Smog Abatement Measure in the South Coast Air Basin

Abstract

It is well known that emissions from motor vehicles are the major cause of smog in the South Coast Air Basin. In an attempt to reduce the smog a strategy has been adopted by the State of California based on the idea of reducing emissions from each vehicle per mile driven rather than restricting the number of vehicles or the amount any vehicle is operated. The principal elements of this strategy are three. The one is a set of emission standards for new vehicles which becomes more severe with each model year until 1975 when the federal emissions standards become effective. The second is a program whereby existing vehicles are retrofitted with one or more emission control devices whenever the Air Resources Board determines that appropriate devices are both effective and available. The third is a system of tax exemptions designed to encourage the conversion of existing vehicles to burn gaseous fuels. This paper discusses periodic motor vehicle inspection and maintenance as a fourth element which could be incorporated into the strategy to complement the existing measures. There is abundant experimental evidence to show that each of the three measures in the present strategy is capable of materially reducing emissions. Unfortunately there is a growing body of data that shows that the measures are often not as effective as they might be. Usually the reason that a measure is ineffective on a particular vehicle is that the vehicle is malfunctioning or misadjusted. It is a truism that any vehicle will emit more if it is malfunctioning or misadjusted than if it is operating properly. Depending on the nature of the malfunction or misadjustment the excess in emissions may be anywhere from a few percent to several hundred percent. For the very low emission vehicles to be produced in the latter half of this decade it is expected that certain not too uncommon kinds of malfunction would increase their emissions by several thousand percent. The periodic inspection and mandatory maintenance discussed below is intended to return improperly operating vehicles to proper operation and thus cause each vehicle to achieve its normal level of emissions rather than some higher level.