California EPA
the 1965 rule was base on twenty year old vehicles . that was revised to the current law on smog tests , a vehicles four years old or less , smogs are not required . these are gas powered vehicles , trucks with diesels have another type of smog requirements . california just made them put after burns on the rigs exhaust to burn up the particular matter from the exhaust or buy a new rig , estamtes cost for the unit installed is 14k , yes 14k . or you can only put 2500 miles on your rig a year . alot of rigs got sold off , just look to the northern states for them , trucking co's scraped alot as well . just thing of all those turbo's getting scraped , should have been buying them up , lol .