The U.S. railroad Amtrak is trying to stir up new business by offering $100 in free alcohol to customers on some overnight trains.

The national passenger rail company is making the unusual offer to promote a new high-end service being offered on a trial basis for certain sleeper car trips.

Members of Amtrak's guest rewards program — the railroad equivalent of frequent fliers — can get a $100 per person credit for alcohol between November and January.

The offer of free drinks comes on top of the dinner wine that is already included in the cost of a ticket for GrandLuxe trips on the California Zephyr — chugging between Chicago and San Francisco — the Southwest Chief between Chicago and Los Angeles, or the Silver Meteor between Washington, D.C., and Miami or Orlando, Fla.

At about $6 for a house wine or $7 for a top-shelf scotch, that credit could fuel a long ride. The credit would not go nearly as far for, say, a $250 bottle of Dom Perignon — also available.

Christina Messa, vice president of marketing for GrandLuxe, said the drinks promotion is part of an effort to revive some of the luxury of old-fashioned, cross-country train trips.

Mothers Against Drunk Driving questioned whether $100 in free alcohol was too much.

"This sounds like a lot of credit toward possible overindulging," said MADD spokeswoman Misty Moyse.

GrandLuxe offers separate cars, with their own private dining and lounge sections, attached to regular Amtrak trains. Tickets for such trips range from $789 per person for a two-day, one night trip on the East Coast to $1,599 or higher for three days and two nights for travel to or from the West Coast.

Amtrak spokeswoman Karina Morero said the goal is to entice people to try the new, high-end sleeper car service. The free alcohol promotion "is a test run so we're going to see how our passengers respond to it," she said.