Inspectors with the air resources board set up a checkpoint on Jensen near Highway 99.
The big rigs were checked for smoky exhaust, as well as whether they were complying with pollution laws. The state began its diesel soot reduction plan in the year 2000.
Some trucks are now equipped with new filters which help clean up particulate matter. And some can be retrofitted with new filters which can reduce the amount of smog released into the air.