Philadelphia and New York City are two of the biggest cities in the United States, conveniently an hour apart via rail. Both cities operate interesting subway systems, which happen to both have an A and B train. This video goes on to compare the two.
In New York City, the B Train in a weekday-only train between Manhattan and Brooklyn, similarly to in Philadelphia where the B train is a weekday only train operating along the Market-Frankford Line.
Routes: A Train, B Train