In some track locations, copper bond wires connect rail ends to carry electric current
across the joint. Such bonded joints are found where highway or train signals are actuated
through track circuit and at gasoline-loading stations where the rails are grounded.
Lugs at the end of the bond wire are driven into holes drilled in the rail's web until they
fit firmly. Except in emergencies, the rail maintenance crew must be careful not to break wires
or remove bonded rails unless a signal maintainer is present. If he is not there when a broken
rail is to be replaced, tighten the joints to make as good contact as possible with the rails, and
notify him that the bond wires have been broken.
Rail joints are connected and strengthened by joint bars. Rails of different sizes are
joined by compromise joints, a variation of the regular joint made to fit the different rail
sections. Unless they are installed in very hot weather, space for expansion is left between the
joints. Standard military practice is for a joint to be located opposite the center of the other rail
of the track--a "broken joint." Joints in electric track-circuit territory must be insulated; in some
locations, they must be bonded.