slew

To slew track is to move an entire rail line horizontally perpendicular to its length, keeping the rails in contact with the ground or on their existing ballast bed. The operation shifts the centerline of the track sideways by some distance, typically a few inches to several feet, without raising or removing the rail itself. This is distinct from realigning track by lifting, which requires disconnecting rail joints and repositioning on new sleepers or ties.

Slewing is performed using hydraulic or mechanical jacks positioned under the rail, usually at multiple points along the section being moved. The rail is lifted minimally, just enough to reduce friction between the ballast and sleeper, then pushed sideways. Once in position, the rail settles back and is secured. The method is faster than full removal and replacement, and causes less disruption to the ballast structure, though it does require careful measurement and coordinated pressure across the jacks to prevent kinking or binding.

Common applications and limitations

Slewing occurs most often in track maintenance and minor realignment work: correcting lateral drift, adjusting curves to improve wheel wear distribution, or shifting a line slightly to clear an obstruction or allow platform reconstruction. It is also used in rail construction to fine-tune track geometry after initial laying. However, slewing cannot correct vertical or longitudinal defects, and moving a line more than a few feet typically requires disconnecting and re-laying sections entirely.

The term comes from the nautical sense of slew, meaning to turn or pivot. In rail work it has narrowed to the specific operation of sideways displacement. The practice is old and remains routine; modern track machines often include slewing capability as part of their tamping or straightening function, though manual methods with hand jacks are still used for small corrections on sidings or branch lines where traffic is light.