Horseshoe Curve, Pennsylvania

A panorama taken in October 1934 (larger version on Wikimedia)

The term Horseshoe Curve denotes a railway track formation that in a short distance substantially changes the direction of travel by about 180 degrees.  The best known one in NZ is the one at Turangarere on the North Island Main Trunk.

The one in Pennsylvania, simply called Horseshoe Curve, is in Kittanning Gap near the summit of the Allegheny Front, about 5 miles (8 km) west of Altoona. It covers about 220 degrees of arc; on the north side, the radius measures 637 ft (194 m), tightening to 609 ft (186 m) on the south side.

It was built with two tracks in 1854 by the Pennsylvania Railroad.  In 1900 it gained an extra two tracks; in 1981 one of them was removed by Conrail.

Four tracks, three trains: a poster scene from the late 1940s