Tractors require more pedal force than road vehicles. The ergonomics literature concerning human strength in the operation of control pedals although extensive is not adequate for a tractor designer. The study was aimed to quantify human strength in the operation of tractor control pedals by Indian operators. The leg strength data of 20 male tractor operators were measured using a strength measurement set-up. The leg (right and left legs) strength data were collected at five horizontal (35%, 40%, 45%, 50% and 55% stature) and six vertical (10%, 13%, 16%, 19%, 22% and 25% stature) locations of foot pedal from the seat reference point (SRP) keeping the lateral distance from mid line constant. The analysis of data indicated that the force exerted by right leg was higher as compared to that exerted by left leg. It was also observed that the fifth percentile male tractor operator could reach 8 10 mm in front and 370 mm below the SRP. The maximum leg strength values of 655 and 613 N for right and left legs, respectively was observed when the pedal was located at 55% stature in front and 10% stature below the SRP i.e. when the leg was in almost elongated position. It was also observed that the actuating force limits as given in IS: 10703 [1992. Agricultural tractors-maximum actuating forces required to operate controls. IS 10703-1992]/ISO/TR 3778 [1987. Agricultural tractors-maximum actuating forces required to operate controls. ISO/TR 3778] are very high as compared to leg strength data of Indian operators. It may be concluded that the optimum location of clutch and brake pedals on Indian tractors should be at 40% stature in front and 19% stature below the SRP based on strength limits and postural comfort of operators. It may be recommended that the limits for maximum actuating force for brake and clutch pedals should be 330 and 280N, respectively. Relevance to industry The study emphasizes the need to optimally locate and design tractor control pedals based on strength limits of operators by the tractor manufacturing industry. This will not only enhance the comfort and safety of the tractor operators but also increase work output from the tractor on per day basis. The findings of the study will also be helpful for tractor operators in other Asian countries. (c) 2007 Elsevier B.V. All rights reserved.
