Some North Shore commuters are scrambling to find a new way to get to work in Boston after a company that has provided commuter bus service for decades announced that it will make its last trip later this month.

When commuters from Boxford, Georgetown, Newburyport, Peabody and Topsfield got on the Coach Company bus that typically shuttles them between downtown Boston and the North Shore in late March, they were greeted by a notice informing them that the company "will be exiting the Boston commuter bus service effective April 19."

The company, which has a corporate office in Merrimac and a garage in Plaistow, N.H., said its decision was based on finances and the lack of a subsidy from the Massachusetts Department of Transportation.

"We had always been subsidized by the State to help operate the commuter service but, in the Duval [sic] Patrick era, we and all the other commuter transportation providers had our subsidy cut," the company wrote in its note to riders. "We did what we could to try and make it work but unfortunately we have reached the point where we can no longer afford to operate the commuter service."

In a brief interview with the News Service, Coach Company owner Benton Smith said two other factors led to the decision to stop Boston commuter service: increases in the company's insurance costs and dwindling ridership.

He said the cost of insuring the company's commuter buses recently doubled due to a change in which the company's buses are now considered to be garaged in Boston rather than New Hampshire because of the commuter runs.

"It's anti-commuter," he said of the changes, adding that his company's buses do not spend the night in Boston and only park there to pick up or drop off riders. "It was crazy ... ours went from a normal charter bus in the $8,000 range and it went to $18,000 for those commuter buses."

He said ridership has fallen off, especially on Mondays and Fridays, meaning the company has just three days a week of a full bus worth of fares. Making matters worse, he said, is the limited parking available at the Newburyport park and ride, which he said was the origin point for the greatest number of riders.

"The operator that runs that facility has it so stuffed with long-term airport parking that the commuters were forced out and it hit our ridership. And that ridership is pretty much what funded the runs," Smith said. "Lower ridership because of parking issues and whatnot and an increase in insurance and no subsidy to help run it, we just to make a business decision."

MassDOT said about 60 people use the Coach Company's commuter service each day and, in a letter that the department has circulated to North Shore municipal leaders and others, said it does not regulate operators like the Coach Company and that MassDOT "does not provide operating subsidies for this or other commuter services provided by private operators."

MassDOT suggested that affected Coach Company riders use the T's commuter rail system or other services operated by Merrimack Valley Transit Authority and C&J Bus Lines. The agency pointed riders with specific needs towards to find alternate travel options.

"MassDOT managers have already reached out to other bus operators to gauge interest in running routes similar to those run by The Coach Company. In addition, The Coach Company will be returning two intercity coaches to MassDOT which the state had provided for the Boston Commuter Service routes so that these two vehicles may be used by another bus service operator," MassDOT wrote. "By April 10, we hope to be able to announce one or more operators who will be offering new service options using these vehicles."

The loss of a commuter bus service from the North Shore could complicate what already looks to be a challenging few years for North Shore commuters. Lane closures began Monday on the Tobin Bridge and next month officials will initiate lane closures on Route 1 in the Chelsea Curves area as part of a rehabilitation of the Tobin Bridge's surface and maintenance of the Chelsea viaduct.

MassDOT expects those projects -- which transit officials have warned will increase travel times for drivers and MBTA bus riders in both directions along Route 1 -- to be completed by 2021.