In 1882, Abt designed his rack-railway system that enabled at least one tooth of the rack to be permanently engaged. He designed a new rack using solid bars with vertical teeth machined into them. Two or three of these bars are mounted centrally between the rails, with the teeth offset. The use of multiple bars with offset teeth ensures that the pinions on the locomotive driving wheels are constantly engaged with the rack. The Abt system was cheaper to build than the Riggenbach because it required a lower weight of rack over a given length. Abt also developed a system for smoothing the transition from friction to rack traction, using a spring-mounted rack section to bring the pinion teeth gradually into engagement.