The Washington DC area subway system seemed a bit complicated to me at first, but eventually I found that it's quite logical. Purchasing metro cards runs as follows: In front of the ticket vending machine, you have to choose if you plan to buy a ticket for a single journey and then look at the list of stations and the cost of the journey to reach it. It varies depending on whether or not it's rush hour. If you want to save time on new cards is better to buy a card that has more money on it than just a single route. To get a card, you have to select a value. The machine suggests $20 to start with and 2 side buttons do raise or lower this amount until you reach the desired price.