PORTLAND – Amtrak’s Downeaster began operating on a new schedule Monday that shaves 10 to 15 minutes off the travel time between Portland and Boston, a change that rail advocates say was necessary to make the train competitive with buses.

The Downeaster is benefiting from track improvements in Kennebunk, faster station stops and schedule adjustments made by the Massachusetts Bay Transportation Authority, Patricia Douglas of the Northern New England Passenger Rail Authority said Monday.

Last year’s lifting of the train’s top speed to 79 mph shaved three minutes off the Portland-to-Boston transit time, and Monday’s changes will shave off another 10 to 12 minutes.

Riding the train from Portland to Boston takes 2 hours, 30 minutes under the new schedule, compared with 2 hours, 45 minutes before the changes, Douglas said.

“From the very beginning, a shorter travel time has been one of the most important issues,” said Wayne Davis, chairman of the Portland-based rail advocacy group TrainRiders Northeast. “This is good news for everyone.”

The Northern New England Passenger Rail Authority, which operates the Downeaster, hopes additional track upgrades will allow a fifth round trip by this fall. Currently the Downeaster makes four daily trips between Boston and Portland.

The Downeaster makes stops in Saco and Wells in Maine; Dover, Durham and Exeter in New Hampshire; and Haverhill and Woburn in Massachusetts. Effective Monday, the Downeaster added its seasonal stop in Old Orchard Beach.

Rail authorities are hoping for a smooth ride this summer.

Last summer, Downeaster officials suspended service during the Democratic National Convention in Boston and then scrambled to assemble train-and-bus service after an overpass buckled during a track overhaul in Kennebunk, necessitating emergency repairs.

The new schedule that went into effect for this summer was the result of the higher speed and improvements of the rail line in Kennebunk, Douglas said. The rail upgrades allowed the speed to be increased from 25 to 50 mph through Kennebunk.

Additional improvements were yielded by making station stops more efficient, shaving the times down to 30 to 60 seconds, Douglas said.

Finally, the MTBA adjusted its schedule that had treated the Downeaster like other commuter trains that made stops between Woburn and Boston, she said. The new schedule takes into account that the Downeaster doesn’t stop between Woburn and Boston.