PORTLAND – With gas prices surging upward again, ticket sales are hot for the Portland-to-Boston Downeaster passenger train.

Winter is usually a slow season for the Downeaster, but this year has been an exception, with ridership for the quarter up 35 percent over last year’s figure. Many of the trains are now sold out days in advance.

To accommodate all of the riders, the Northern New England Passenger Rail Authority has added a car to one of its trains during school vacation week. The rail authority says it is now talking to Amtrak about getting an extra car for the tourism season ahead.

“We’re looking into the summer with Amtrak to see what they might have available, because we may need to have that extra car at least as much as we can during the summer,” the authority’s Lou Ensor told WCSH-TV.

Rail service officials say the gain in ridership is because of the high price of gas, shortened trips to Boston and the Downeaster becoming recognized as a dependable way to travel. It rates near the top of Amtrak trains for on-time service.

The Downeaster, which marked its fourth anniversary this week, is no longer considered a novelty and is used regularly by commuters. Transportation officials are looking into extending its Maine runs to Brunswick.

Worries of high gasoline prices this summer were heightened Thursday as oil prices hit a record high of $72.49 after a drop in U.S. gasoline stocks.

That has prompted concern that refiners lack an adequate inventory cushion ahead of the peak summer driving season, which could translate into higher prices at the pump.