smog check aftermarket parts

On-Road Heavy-Duty Regulations & Certification Programs

The millions of vehicles operating on California's roadways each day are the single greatest source of smog-forming emissions in the state, and a top contributor to climate-changing gases. Keeping trucks and buses well-maintained and in good working order is a key part of the state’s pollution control program. Heavy-duty engine requirements help to keep pollution from trucks and buses down even as the number of motor vehicles - and the miles people drive them each day - continues to grow.