@grunt - how they didn't get electrocuted is physics 
There are four rails on the underground. The two that the wheels run on have a very low current in some places, but not anything that would bother a human being.
The rail in the middle of the tracks (second one from the platform) is the negative rail. It could kill you if a train was on the same segment of track and returning current, or if you were in contact with the positive rail at the same time, otherwise it should be fine. The proper scary rail is the one furthest from the platform, and furthest away from the Buggy.
I'm sure it goes without saying, but just in case: Do not put this information to the test, and do not trespass on the railway.