Meet Farecard.

Farecard is a wallet-sized ticket containing a strip of magnetic tape that will be the Metro subway rider's passport.

Farecards can be purchased from vending machines in any Metro station. The machines accept $1 and $5 bills and nickels, dimes, quarters and half-dollars. Cards can be purchased for amounts between 40 cents (the minimum cost of one ride) and $10. The machine makes change. For example, if a rider puts $1 into a machine but only wants a 40-cent Farecard, he can adjust the machine so that he receives 60 cents in change and a 40-cent Farecard.

If he has an old Farecard with less than 40 cents value remaining, he can insert the old Farecard in the machine, add money, and receive a new Farecard that contains the total value of his old Farecard and his money.

After buying a Farecard, the rider inserts the card into the side of a computerized box that controls gates leading to the train platform. The card must be worth at least 40 cents before the gates will open. If there is enough money in the card, the card will appear within a second at the top of the computerized box. When the rider takes the card, the gates open and the rider walks through.

The rider must keep the card.

At the end of the subway ride, the rider approaches the computerized box again and inserts the card. Three things can happen:

1. If the cost of the trip equaled the amount of money left in Farecard, the box will keep the card but the exit gate will open.

2. If the cost of the trip was less than the amount of money left in Farecard, the box will return Farecard and print the balance left in Farecard on its face. The gate will open. The rider returns the card for his next trip.

3. If the cost of the trip is more than the amount left in Farecard, the machine will light up, say, "Go to Addfare" and return the Farecard. The gate will not open.

Addfare is another machine. It stands inside the exit gate. The rider will insert his returned Farecard in Addfare. Addfare will figure out how much money the rider owes and will announce same in a digital readout.

Rider inserts money into Addfare's coin slots, retrieves Farecard, his change (if any) and returns to the exit gate, where he tries again. This time the gate should open.