These exits from the Wiehle Avenue garage will be more crowded on Monday. (Robert Thomson/The Washington Post)

If the line to exit the new Silver Line garage is really slow on Monday, keep this in mind: Some Metro commuters who used to ride a bus to a station may not have their SmarTrip cards set up for parking.

SmarTrip card Metro image shows a SmarTrip fare card.

Granted, we’re talking about a limited pool of travelers, but it doesn’t take much to slow an exit line from a station garage, and even less to annoy the drivers waiting in the line.

The group in question consists of commuters who were traveling by bus, who are part of the SmartBenefits program and who are planning to use their SmarTrip cards to pay for the station parking at the Wiehle Avenue garage.

SmartBenefits is the program under which people get federal tax breaks by setting aside a portion of salary for transit commuting. Several years ago, the IRS tightened up the rules. The value flowing into a SmarTrip card lands in one of three baskets: One is the money a person adds to a card, and it can be used for any purpose payable with the card. A second basket pays for transit riding. A third will cover parking at Metro stations.

The SmarTrip card won’t pay for parking with the money set aside for transit riding. It will deduct any value you have added on your own, but that’s not part of the commuting tax benefit program.

A person who has been riding a Fairfax Connector of Metro bus to a station may not be set up under the SmartBenefits program to pay for parking with a SmarTrip card. If there’s no money at all on the card to cover parking, the card won’t work at the exit. Many people set up their benefits plan long ago and may have no recollection of this complicated system of separate baskets flowing onto the cards.

Quick solutions: Add enough value to your SmarTrip card on Monday to cover the daily $4.85 for parking when leaving the garage. Or use a credit card.

Long-term solution: Contact the administrator of your SmartBenefits program to realign your commuter benefit allocation to cover the parking cost. The benefit for parking can be up to $250 per month. The transit-riding benefit is up to $130.