I'm relatively new to New York and ride the subway every day. When I'm on the above-ground lines I notice another "fourth" rail in between the two running rails that doesn't look like it is used, but is securely tied down. Sometimes there's even a fifth rail, also in the middle. Usually this rail doesn't run continuously and it occasionally curves or has other oddities. What is this fourth rail for? [more inside]
posted by pithy comment on Mar 23, 2007 - 15 answers

Is there a geographically accurate map of the DC metro system? Like this London tube map?
posted by phrontist on Dec 28, 2006 - 11 answers

How far from New York City can one get solely by using public transport? [more inside]
posted by armage on Oct 10, 2006 - 22 answers

What do our (United States) roads really cost? [more inside]
posted by R343L on Sep 19, 2006 - 10 answers