Weekday service between Brunswick and Dover, New Hampshire, will be limited and passengers on most of the line should expect to take part of their trip by bus, said Patricia Quinn, executive director of the Northern New England Passenger Rail Authority. Weekend service will operate normally, but there will be construction delays, Quinn said. Most fares have been reduced during the construction period.

Pan Am Railways, along with NNEPRA and Maine Department of Transportation is replacing about 15,000 railroad ties and restoring a number of grade crossings on its line in Maine and New Hampshire. Construction is expected to begin on Saturday, Sept. 8 and wrap up by Oct. 5.

Disruptions could throw a wrench in a lot of travel plans. In 2017, more than 50,000 riders took the Downeaster in September, the third-highest ridership month of the year for the passenger rail.

“We tend to do these in October, but again there are competing projects for Pan Am as well. We moved it a little earlier this year than in the past,” Quinn said. “There is really never a good time to do these projects, this is just where this one wound up.”

The biggest travel disruption will be next week, according to a Downeaster schedule. From Sept. 10 to 16, the early morning and midday southbound train will not run during the weekdays, and neither will the second northbound run of the day.

There will be no stops at all in Saco and Old Orchard Beach, and the run between Dover and Brunswick will be operated by shuttle bus during the first week of construction.

Service gets marginally better on Sept. 17. The first southbound train of the day will not operate between Brunswick and Wells, and the midday southbound train will not run at all. The second northbound train of the day also won’t run between Boston and Dover, but it will pick up again between Wells and Brunswick.

There will be no weekend Downeaster service to Woburn, Massachusetts, until Oct. 28 because Massachusetts Bay Transportation Authority is conducting work on the track.