One of Indiana Harbor Belt's unique traction slugs. These provide extra tractive effort to the accompanying SW1500's without the need for additional horsepower ... very useful for pushing/pulling... (more)

A roster shot of a slug unit termed by IHB as a Diesel Hump Trailer. The SW1500 (to the left of the DHT) is "permanently" paired with it.

IHB keeps a unique roster of units to add traction and power to its switching pool. Here is Hump Trailer #479 attached to IHB 1523.