Legislation designed to strengthen federal safety regulation of trucks and buses won the strong support this week of the administration and the Teamsters Union.

In two days of hearings before the Senate Commerce Committee, both John Hassell, deputy administrator of the Federal Highway Administration, and R. V. Durham, director of safety and health for the International Brotherhood of Teamsters, said that federal action was necessary to stem the accelerating accident rates involving commercial motor carriers.

"There is strong reason to believe that this increase in accidents results from widespread noncompliance with safety requirements," Hassell said. He noted that in May, federal and state officials stopped 1,731 trucks at random in five Mississippi Valley states for safety inspections and found 753 of them - 44 percent - unfit and placed them out of service.

"We do not place vehicles out of service because of minor violations," he emphasized. "We are talking here about unsafe brakes and other significant safety hazards." The May inspection was not unrepresentative, he added.

The teamsters' Durham agreed, calling the state of trucking safety "a disaster."

"In some areas of the industry, there are differing degrees of compliance with existing safety regulations, but overall the system is in need of change," he said.

There was one serious disagreement between them Durham sought to link truck safety regulation to the economic regulation also undergoing congressional scrutiny, arguing that safety regulation wouldn't be effective without continuing the extensive economic regulatory scheme.

Hassell called it a "false" issue saying there were no studies proving a causal link and that DOT data suggested the safety performance of federally regulated and unregulated carriers was comparable. "Safety laws are what we need to assure safe motor vehicle operation," he said.