Originally NMR was modelled on the Rigi system invented by rack railway pioneer Nicholas Riggenbach in 1871. Riggenbach himself travelled to The Nilgiris to push the project. However, finally the ABT system invented by Riggenbach's apprentice was preferred as it was less costly and safer. Carl Roman Abt was a Swiss mechanical engineer, inventor and entrepreneur. He made groundbreaking innovations in rack-and-pinion railways, giving his name to one of the most widely used systems developed for mountain railways, the ABT (Alternate Biting Tooth System) rack system.