United States vehicle emission standards are set through a combination of legislative mandates enacted by Congress through Clean Air Act amendments from 1970 onwards, and executive regulations managed
Smog in the Los Angeles valley in 1972
All electric/battery cars, like those of Tesla, are considered zero-emissions vehicles (ZEV) under California's ZEV mandate.
Non-road engines include railway locomotives like this EMD GP38 modified to meet Tier 4 standards.
A representative dynamometer-based emissions test station
The California Air Resources Board is an agency of the government of California that aims to reduce air pollution. Established in 1967 when then-governor Ronald Reagan signed the Mulford-Carrell Act,
United States vehicle emission standards
…has generally been the exception, having been granted a waiver and given allowance to set stricter standards as it had established its own via the California Air Resources Board prior to the 1970 CAA amendments. Several other states have since also received waivers to follow California's standards, which have also become a de…
California Air Resources Board Laboratory, Los Angeles, in 1973
Researchers at the Statewide Air Pollution Research Center manufacture smog using a photochemical tube reactor (May 1972).
Sunlight filtered through smog near Blythe, May 1972
GM EV1