• A backshunt is a railway track configuration in situations where a change in (almost opposite) direction is required and a traditional curve cannot fit.

1. To climb or drop a steep incline using a Zig zag (railway)
   Zig Zag (railway)
   A railway zig zag, also called a switchback, is a way of climbing hills in difficult country with a minimal need for tunnels and heavy earthworks. For a short distance , the direction of travel is reversed, before the original direction is resumed.A location on railways constructed e.g...
   
   
2. To change direction on to a parallel track, often used in industrial sidings.

Example Backshunts

• Part of the old Cleator and Workington Junction Railway
  Cleator and Workington Junction Railway
  The Cleator & Workington Junction Railway was located in West Cumberland in Northern England, serving the towns of Cleator Moor and Workington and intermediate villages...
  
   was maintained in Rowrah
  Rowrah
  Rowrah is a village in Cumbria and spans the civil parishes of Arlecdon and Frizington and Lamplugh. The majority of Rowrah is within Arlecdon and Frizington...
  
   as a backshunt from Rowrah Head Quarry on to the Whitehaven, Cleator and Egremont Railway
  Whitehaven, Cleator and Egremont Railway
  The Whitehaven, Cleator and Egremont Railway was a standard gauge railway in Cumberland, England. It opened for goods traffic in 1855 and for passenger traffic in 1857.- Route :...
  
  . (Google Maps Overlay)