Metro is trying to prepare commuters for a major shift next week in the way they pay for parking at 33 lots and garages across the region.

On Monday, the transit agency will stop taking cash at the exits of its parking facilities, part of an effort to regain public trust following allegations that cashiers were not turning in the money, Metro officials say. An internal audit revealed that Metro might have lost as much as $1 million in annual parking revenues during the past few years.

Starting Monday, drivers must pay for parking with electronic SmarTrip cards. The prepaid, reusable cards will make parking simpler and speedier, officials say. No longer will drivers fumble through wallets for cash or scour seat cushions for change. With a tap of the card to a sensor at every gate, motorists' fees will be deducted automatically from the card.

The cashless system is so painless, Metro officials say, that nearly 80 percent of rail riders who use parking facilities already pay with SmarTrip cards.

But for patrons accustomed to paying with greenbacks, the cash to card switch can be a bewildering process.

On a recent afternoon at the Huntington station in Alexandria, members of the Huley family spotted a sandwich board advertising Metro's upcoming switch to a cashless system, and they snatched up a brochure, figuring it would tell them all they needed to know.

Instead, the Huleys were stumped.

"It doesn't indicate whether it's $5 per month or $5 per member," said George Huley of Alexandria, standing in the station's stuffy garage with his wife, Cathy, and their two children, Hilarie and Christian.

"The question I've got which has not been answered is how much it costs to park," said Cathy Huley, scanning the brochure.

"I feel badly for the people who, when they try to park here on the 28th, they have no idea," she said.

Metro officials say they are trying hard to prevent that. The agency has placed signs and brochures at stations, taken out newspaper and radio ads, published information on its Web site, and staged SmarTrip sales events at several stations. Metro also plans to install 50 SmarTrip vending machines at stations by Monday.

"We've been working hard to get the word out as much as we can," said Metro spokesman Steven Taubenkibel.

Metro plans to post extra employees at parking facilities next Monday, Tuesday and Wednesday to help commuters navigate the new system.

Workers were tinkering with the innards of the Vienna/Fairfax-GMU station's three new SmarTrip card vending machines on a recent evening while Metro representatives hawked cards from a table nearby. Perplexed-looking commuters flocked to the table to buy cards and ask questions: Do you need a separate card to pay Metro fares? Does it already have money on it? Can you get out of a parking lot without a card? No, no, and yes, they were told.

Drivers, they learned, can purchase the cards for $5 each from the new SmarTrip vending machines at stations with parking facilities. They can also buy them online at Metro's Web site (www.MetroOpensDoors.com), by mail and at Metro sales offices and 14 Giant supermarkets in the region. SmarTrip cards come with no value, but drivers can add up to $200 to the cards at machines marked "Passes/Farecards" in all Metro stations.

The cards can be used to pay parking fees -- in most cases $3.75 per day, counting the increases approved by the Metro board this month -- and fares for all Metrorail and some Metrobus trips. At most parking facilities, the fees will be collected on exit during regular hours Monday through Thursday, and from Friday mornings to 3 a.m. Saturdays, when Metrorail extends its hours of service. At a few stations, drivers will continue to be charged on entry, rather than exit.

Starting Monday, customer service representatives will patrol parking facilities to address problems, Taubenkibel said. If a lot is full, for instance, an employee will close it so motorists are not charged if they do not find parking. In the event of broken SmarTrip vending machines or damaged cards, drivers will be able to pay for parking with regular paper Farecards, transit officials said. Metro employees will not handle cash.

Metro will allow a grace period covering the first few days of next week, when unaware commuters without SmarTrip cards might be allowed to exit a parking facility without paying. However, if people abuse the privilege, Metro officials said they will use license plate numbers to track down defaulters, sending notices of unpaid fees and involving the police if necessary.

Metro officials are crossing their fingers that Monday's transition will be smooth, Taubenkibel said.

Aldean Glover, for one, thinks that's wishful thinking. Glover, a Pentagon employee from Woodbridge, began paying for parking with SmarTrip in March. But it took her several reads through the pamphlet, a trip to an information booth and a phone call to Metro headquarters to understand the cards, she said.

As she washed the windshield of her black Honda in the Huntington garage the other afternoon, Glover predicted the "awful" change would frustrate drivers -- especially tourists -- and hurt Metro's business. "It still doesn't make much sense to me," she said.

Staff writer Lyndsey Layton contributed to this report.

Metro officials say about 80 percent of regular parkers already use SmarTrip cards.