Double track? Let's just say multiple. Sacramento has lines where there are 3 or 4 tracks, with 2 light rail and the others "steam" railroad. Any of them, in any direction, can trigger the gates on approach. There have been a number of wrecks with light rail, because it tends to run faster and because it's a quiet zone sop they just use the gong. Sound walls make it worse, because the train operator often can't see the road away approaching the crossing in time to react to a crazy passing a line of other cars waiting for the down gate to enter the crossing wrong way. The south (or Blue, or whatever they call it now) line is particularly bad that way, and will probably become worse once ACE starts running that way (only a few freight trains a day now so most of the traffic is light rail).

As Bob2 says, it's hard to make this chimp-proof.