strap rail

A strap rail is an early form of railroad track in which a flat iron strap, typically 1.5 to 2 inches wide and three-eighths inch thick, is spiked or bolted to the top surface of a wooden rail. The wooden rail itself, often made of oak or other hardwoods, runs the length of the track bed and provides structural support. The iron strap serves to reduce wear on the wood and provide a smoother, harder surface for the wheel flange to roll upon.

Strap rail represented a compromise between the all-wood track of turnpikes and the fully flanged iron rail that eventually became standard. It was widely used on American and British railways from roughly 1830 through the 1850s, when it began to be displaced by rolled iron rails of T-section and later flat-bottom designs. The wooden substrate kept initial construction costs lower than all-iron track, which mattered greatly for early railroad companies building hundreds of miles of line.

Failure modes and limitations

The joint between strap and wood created chronic problems. Vibration from passing trains would gradually loosen the fasteners, and moisture penetration beneath the strap caused wood rot. Once rot began, the entire section had to be replaced. More serious was the tendency of the strap to curl upward at the ends and separate from the wood, creating a hazard called a snake head that could derail equipment. The strap offered minimal lateral stiffness compared to a full rail, limiting safe speed.

The rise of heavier locomotives and higher speeds made strap rail obsolete. Its appearance on a line was a reliable indicator of older construction dating to the pre-Civil War era in America. By the 1880s, strap rail had entirely vanished from main lines, though isolated sections lingered on minor spurs and industrial branches well into the twentieth century. The term itself persists in railroad historical literature but is rarely encountered in modern operations.