In message , Sawney Beane
writes
There are different parts of a rail to measure from, so I took a steel
tape to measure the track alongside the municipal parking lot. While I
was there, the crossing arms came down and traffic backed up and no
train came.

I guess the crossing might detect the trains approach when the rails are
shunted. By a metal measuring tape for instance?

--
Clive Mitchell
http:/www.bigclive.com