WASHINGTON (AP) — The Trump administration took a key step Wednesday toward relaxing federal rules that govern the length of time truck drivers can spend behind the wheel, a move long sought by the trucking industry but opposed by safety advocates who warn it could lead to more highway crashes.

The Federal Motor Carrier Safety Administration, an agency of the Transportation Department, issued proposed changes to the “hours of service” rules , which dictate breaks truckers are required to take, and their time on and off duty.

“It puts a little more power back in the hands of the drivers and motor carriers,” said Raymond Martinez, head of the federal safety agency. Martinez said the agency listened to drivers and their calls for safer and more flexible rules.

But highway safety groups have warned that putting the revisions into place would dangerously weaken the regulations.

“The agency is offering flexibility without regard for the fact that it could be exploited by the worst actors in the industry, including drivers who will operate while fatigued and motor carriers who will coerce them to do so,” said Harry Adler, executive director of the Truck Safety Coalition.

There were 4,657 large trucks involved in fatal crashes in 2017, a 10% increase from the year before, according to a May report issued by the agency. Sixty of the truckers in these accidents were identified as “asleep or fatigued,” although the National Transportation Safety Board has said this type of driver impairment is likely underreported on police crash forms.

Trade groups that represented truck drivers and motor carriers have pushed for years for less rigid hours of service rules, arguing that the regulations were too rigid and out of step with the daily realties confronting most truck drivers. They found a supporter in President Donald Trump, who has made rolling back layers of regulatory oversight a priority.

“To me, having the flexibility is huge,” said Terry Button, a hay farmer from upstate New York who owns his truck and has logged about 4 million miles since he started driving in 1976. “It’s good that the government finally took the time to listen to the people who do the job.” Button spoke to The Associated Press on Wednesday.

The existing regulations limit long-haul truckers to 11 hours of driving time within a 14-hour on-duty window. Drivers must have had 10 consecutive hours off duty before the on-duty clock starts anew.

A driver who is going to be driving for more than eight hours must take a 30-minute off-duty break before hitting the eight-hour mark.