Much of the Washington DC Metro area is biker friendly, and Metrorail is no exception. If you ventured a little bit too far, ran into a summer storm, or just want to cover a little bit more ground, this can be an excellent option.
Bikes are not allowed during Metro's busiest hours. This includes weekdays from 7-10 a.m. and 4-7 p.m., as well as the 4th of July and other particularly busy occasions. You are also asked to limit bicycles to four per car, and enter cars using the first and last door of each car.