Oregon presently does not include diesel buses or trucks weighing more than 8,500 pounds in its emissions testing program. But because diesel engines pump more than three times more particulate matter - soot and smoke - into the air than their gas-burning counterparts, state officials are considering the regulation of trucks and buses as one way to help clean up Oregon’s air.
“We’re not very far down the road yet, but this is something we’re seriously considering,” said Ed Woods, who oversees the Oregon Department of Environmental Quality’s vehicle inspection program.
The idea comes at a time when the Environmental Protection Agency, to comply with the Clean Air Act, is poised to tighten air quality standards. The changes are scheduled to go into effect in June.
“The new standards are one thing, but we’ve also run into the perception problem of people wondering why (diesel) trucks aren’t treated the same way as cars,” Woods said.
In part, buses and heavy trucks aren’t tested because there are no federal requirements, officials said.
“A lot of it has to do with the nature of trucks and their routes,” explains Greg Green, the DEQ’s air quality administrator. “It’s hard to tell a truck that’s registered in Oregon that it has to meet a certain standard here when it spends 95 percent of its time outside the state.”
Oregon motor vehicle and transportation records list more than 326,000 vehicles weighing more than 26,000 pounds. Most of those operate on diesel.
In all, more than 450,000 trucks registered in the state weigh more than 8,500 pounds; this category includes a larger number of gasoline-powered trucks.
Current DEQ testing procedures, conducted in most of the state’s population centers, measure the amount of carbon monoxide, hydrocarbons and particulate matter emitted by each vehicle.
A 1993 federal law forced companies that produce diesel to remove some of the sulphur, which reduced the amount of emissions, but diesel still doesn’t burn as cleanly as gasoline.
Smaller diesel vehicles are allowed to emit 20 percent more visible emissions than comparable gas-powered vehicles.
In most cases, the trucking industry has bristled at emissions standards for diesel trucks, which would require costly upgrades. Some clean air advocates want all diesel trucks outfitted with particulate traps, devices that catch most of the particulate matter emitted in truck exhaust.