In a letter to U.S. House of Representatives members sent this week, Teamsters Union President James Hoffa denounced two potential amendments to legislation saying they will weaken highway safety standards by putting fatigued drivers on the road in bigger, heavier trucks.

Hoffa urged representatives to oppose any floor amendments to an appropriations bill that would delay, revise or replace the current hours of service 34-hour restart provision or allow increases in truck size and weight.

“The tragic accident that claimed the life of comedian James McNair and injured many others including actor Tracy Morgan, could have been prevented had Walmart’s driver been properly rested rather than reportedly going 24 hours without a break,” Hoffa said. “While the notoriety of the victims in this accident pushed truck safety to the front page, more than 4,000 lives are claimed each year on our highways as a result of accidents involving trailer trucks. We must ensure that hours of service rules provide enough rest for drivers so cumulative fatigue doesn’t put the driving public at risk.”

Last week the Senate Appropriations Committee voted by a wide margin to suspend the current 34-hour restart provision of the hours of service rule while the Federal Motor Carrier Safety Administration studies the impact of the regulation. The vote was applauded by the American Trucking Association and the Owner Operator Independent Drivers Association. The measure still faces a long and uncertain road, before possibly receiving final approval.

The vote has drawn blowback by some safety groups following the crash last Saturday in which Walmart trucker Kevin Roper struck the limo van of Morgan and others in New Jersey. Police in court papers claim Roper had been awake for more than 24 hours, a crime in the state if someone causes a traffic accident with injuries. Police have yet to say how they discovered Roper had been awake this long, while messages on a Twitter account purportedly from Roper deny such a claim.