To discourage cancellations and no-shows, Alamo Rent A Car said yesterday it will reward customers who pre-pay and penalize those who don't follow through.

Under the plan, customers who pay when making a reservation at Alamo.com get a 10 percent discount on the base rental price. Here's the twist: A customer who then fails to show up, or cancels within 24 hours of a scheduled pickup, is nicked with a $25 credit-card charge. Cancellation more than 24 hours in advance carries a $10 fee.

The Alamo policy, effective immediately, is unique among major rental agencies. It's the latest wrinkle in the industry's persistent efforts to address the problem of no-shows. Past efforts to penalize customers who don't follow through with reservations have largely failed.

Alamo spokesman Charles Pulley says the company hopes the change will encourage customers to make firmer plans, and allow the company to manage its fleet better.

Alamo's move differs from some past industry efforts by incorporating "a carrot approach" — the 10 percent discount — to help cut down on the number of no-shows, says Sherb Brown, publisher of Auto Rental News. No-shows have eaten into the industry's bottom line for years. And unlike airlines or hotels, car rental companies have had difficulty levying cancellation fees.

Brown said about 30 percent of reserved cars aren't picked up. But stiff competition has prevented companies from doing much about it, he says.

Hertz and Dollar Thrifty said they don't plan to follow Alamo's lead.

"We've looked at cancellation fees over the past year, and determined that strong customer preference is (to retain) flexibility," says Rich Broome, a Hertz spokesman.

Broome says the notion that no-shows are disruptive is overblown. Many of the no-shows occur in situations that are predictable — bad weather that has diverted flights, for example. "We have the experience to know the likelihood of cancellation," he says.