PORTLAND — Just in time for the busy summer travel season, Maine is increasing the speed limit on most of Interstate 295 and long sections of the state-run portion of Interstate 95, but motorists will have to wait until later in the summer to go faster on the Maine Turnpike, officials said Tuesday.

Speed limits will increase from 55 mph to 60 mph and 65 mph to 70 mph on rural sections of I-295 and I-95 as soon as signs are installed Tuesday and Wednesday, Transportation Commissioner David Bernhardt said. A section of U.S. 1 between Brunswick and Bath also will be boosted, from 55 mph to 60 mph.

The Maine Turnpike Authority is poised to raise speed limits from 65 mph to 70 mph for most of the toll highway, but that requires a different process that won’t be completed until mid-August, a spokeswoman said.

Bernhardt said most motorists are already driving faster and that the new limits will be safer.

“The fact of the matter is people drive at their comfort level. All studies show that if you post it too low, then you have more accidents. If you post it higher, then you have more accidents,” he said. “It’s not necessarily the speed that causes the crashes. It’s the differential in people driving at different speeds.”

But greater speeds will increase the number and lethality of crashes, said Russ Rader, spokesman for the Insurance Institute for Highway Safety, a nonprofit research group funded by automobile insurance companies.

“When you increase the speed limit, you make it less likely that drivers facing an emergency will be able to brake in time to get the speed down to a survivable point,” Rader said. “Raising the speed limit gets people to their destinations faster, but there’s always a cost,” he added.

The speed limit for most of the state’s interstate highways was 65 mph, except for a 110-mile stretch between Old Town and Houlton, where motorists can drive 75 mph.

The Maine Legislature approved a bill in 2013 that allowed the transportation commissioner to raise all interstate speed limits to 75.

The biggest stretches of highway seeing speed limit increases from 65 mph to 70 mph are I-295 between Portland to Gardiner, and I-95 between Augusta and Oakland, and Fairfield and Bangor. I-95 through Bangor and Brewer will increase from 55 mph to 60 mph and the stretch between Brewer and Old Town will go from 65 mph to 70 mph.

Critics suggest motorists will become comfortable with higher limits and drive even faster. But that’s not the case, Bernhardt said. Officials revisited the 75 mph speed limit north of Old Town and found that speeds increased only 1 mph since the higher limit went into place in 2011, he said.