The Rimutaka Incline was a 3-mile-long (4.8 km), 3 ft 6 in gauge railway line on an average grade of 1-in-15 using the Fell system between Summit and Cross Creek stations on the Wairarapa side of the original Wairarapa Line in the Wairarapa district of New Zealand. The term "Rimutaka Incline" is sometimes used incorrectly to refer to other parts or all of the closed and deviated section of the Wairarapa Line between Upper Hutt and Speedy's Crossing, near Featherston. The incline formation is now part of the Remutaka Rail Trail.

The Fell system was the first third-rail system for railways that were too steep to be worked by adhesion on the two running rails alone. It used a raised centre rail between the two running rails to provide extra traction and braking, or braking alone. Trains were propelled by wheels horizontally applied and retracted by springs onto the centre rail, controlled from the cab, as well as by the normal running wheels. In practice, the running wheels could be allowed to run freely to reduce wear, but the centre brake shoes needed to be replaced frequently. For example: the locomotives' shoes were replaced after each journey on the Mont Cenis Pass Railway. Extra brake shoes were fitted to specially designed or adapted Fell locomotives and brake vans, and for traction the prototype locomotive had an auxiliary engine powering the horizontal wheels. The Fell system was developed in the 1860s and was soon superseded by various types of rack railway for new lines, but some Fell systems remained in use into the 1960s. The Snaefell Mountain Railway still uses the Fell system for (emergency) braking, but not for traction.