In railway terminology, the "four foot" is the technical name for the area located between the two running rails of a single track. Despite its name, the space is actually slightly wider than four feet in standard gauge systems; specifically, it is 4 feet, 8.5 inches (1435 mm). This area is extremely dangerous and is a "no-go" zone for anyone not specifically trained and authorized in track safety. Workers are taught the "jargon" of the track to ensure clear communication: the area outside the rails is called the "four-foot's companion," the six-foot is the space between two adjacent sets of tracks, and the ten-foot is a wider gap often found between pairs of lines. Understanding the "four foot" is essential for track maintenance safety, as it is where a person is most at risk of being struck by a train. In many modern systems, the four-foot also houses critical infrastructure like "balises" for automated train protection or third-rail power systems, which carry lethal electrical currents.