But many people do have cars, arguably a larger number than trucks. Many of them letting it idle for fairly long periods of time in the winter to remove ice, in the summer for air-conditioning if waiting for someone, etc. So on the aggregate, they are still producing a high number of fumes.

Also, if the business requires the truck to idle to run loading, unloading, and processing equipment, then the law exempts them from the requirements while using that equipment.