Editorial: Diesel trucks are among California’s biggest polluters. Smog-check them

Trucks make their way up the Gerald Desmond Bridge at the Port of Los Angeles on July 19.
(Wally Skalij / Los Angeles Times)

The routine smog check is one of the basic requirements of owning a car in California. Older cars have to be taken to the shop every other year to ensure that they have been properly maintained and don’t spew excessive emissions from their tailpipes.

But even though heavy-duty diesel trucks are among the biggest polluters in the state, truck owners don’t have the same responsibility. That would change under a bill by state Sen. Connie Leyva (D-Chino). Leyva’s proposal would direct the state to create a smog check program that diesel-powered big rigs would have to comply with in order to drive on California roads.

Requiring a smog check for trucks is long overdue. Currently, with the number of unhealthy smog days in Southern California on the rise after years of improvement, it’s especially important to finally crack down on truck pollution.


Smoggy, unhealthy air is particularly bad in inland communities in Southern California and the San Joaquin Valley, where trucks play a crucial role in the agriculture and goods-movement industries. About a million heavy-duty diesel trucks operate in California each year, which is a small fraction of the total number of vehicles on the road. Yet diesel trucks account for nearly 60% of the smog-forming nitrogen oxides and 80% of the soot from motor vehicles.

As of now, state regulators have no good way to make sure trucks’ emission controls are regularly inspected and repaired.

Air quality regulators have recognized that diesel trucks produce a disproportionate share of the state’s air pollution woes. Newer trucks are required to have modern pollution controls and on-board monitoring systems that can cut smog-forming emissions by 90%, compared with older truck engines. Soot filters can also dramatically reduce the amount of fine particles spewed into the air.

But all that pollution-control equipment has to be carefully maintained to keep emissions low. One truck with malfunctioning equipment can emit as much pollution as multiple properly maintained trucks.

Yet as of now, state regulators have no good way to make sure trucks’ emission controls are regularly inspected and repaired. New trucks are required to demonstrate that they meet emissions standards, but after that, the state relies on random inspections at border crossings and weigh stations, where officials look for visibly soot-belching exhaust stacks. Fleet owners are supposed to check their trucks once a year to make sure their vehicles aren’t pumping out smoke, but such a visual inspection can’t curtail invisible pollutants that foul the air.

Indeed, without an inspection and enforcement program like the one Leyva is proposing, California’s truck pollution control requirements are toothless once the trucks are in operation. The California Air Resources Board has been slowly working to develop a truck inspection program. Leyva’s Senate Bill 210 would make such a smog check program mandatory within a few years.


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Under the bill, truck owners would be required to pass the smog test to operate in California. There would be a smog-check fee to cover the cost of the program. Regulators would have to develop a system for out-of-state trucks to prove compliance or get tested upon driving into the state, ensuring that they follow the same rules as California-based trucking companies.

The bill would also require the Department of Motor Vehicles to track and confirm that a truck’s pollution control system is working before its registration is renewed or the ownership is transferred — just as the agency does now as part of the smog check program for cars.

Leyva’s bill is facing opposition from some trucking and farming industry groups, which have raised concerns about the fee and the added regulatory burden of the program. But other trucking groups have been open to the program because it would level the playing field between companies that spend the money to properly maintain their trucks’ pollution control systems and companies that don’t.

The smog check program for cars, which has forced gross polluters to clean up or get off the road, has been an integral piece of the state’s fight against smog. It’s time for trucks to be brought into that fight.

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