A rail joint is a device that connects two pieces of rail on a railroad track. This is typically a piece of flat steel with two holes drilled at each end. The holes correspond to ones that are drilled into the ends of the rails and are bolted between the two rails to connect and hold them together. The rail joint also provides room for expansion when subjected to very high heat climates.
Railroad rails are made of high quality steel. Like all steel, they will tend to expand or get longer when sitting in the sun. If the growth for the entire line had to occur at the end of the line of track, the track might need to extend hundreds of feet or more. By placing a rail joint in the rail at a certain interval, the track expansion is allowed to occur at the joint and is not noticeable at the end of the line of track.
Many times a rail joint will be installed near road crossings. This allows repair crews to remove pieces of track with ease. If not for the rail joint, the track would require cutting and welding to be removed and replaced. Often a rail joint is utilized near rail crossovers or switching points as well. Repair crews can once again remove the switch track with ease and replace it without closing the line for an extended period.
New railroad tracks are welded, for the most part, to allow for high-speed train travel. This track gives of a smooth whir as the train's wheels pass along its surface. Older or slower speed tracks can be identified by the rhythmic click, click as the wheels pass over each rail joint. It is said that early in the railroad's history, a good brakeman could time the speed of his train by measuring the time between clicks and rail joints.
Modern construction methods have made welding track the predominant method of laying new or repairing existing track. The rail joint continues to have a place in the rail system, due to the easy removal and replacement characteristics it possesses. Until such time as a faster method of cutting and welding track presents itself, the rail joint will continue to be installed in sensitive areas of track that contain switches, crossings and high heat, making it a crucial component of railroad construction.