The Acceptability of Control Locations and Related Features in Agricultural Tractor Cabs

Five clinics involving 172 tractor operators from North America and Europe were conducted to evaluate 69 different tractors produced by various manufacturers. Human factors and usability concerns were the primary focus of the evaluations. Two categories of data — physical measures from the vehicles and subjective ratings from participants — were gathered. The physical data consisted of control locations (in 3D space), control travel, and force requirements. Subjective data consisted of hundreds of 5–point acceptability ratings from each participant. The physical data were used to create polynomial regression equations (or models) showing the relationships between an individual physical variable, such as the fore/aft placement of a control, and the subjective acceptability rating for that particular variable. The models and overall results show that (1) there is tremendous design variability within agricultural tractor cabs, (2) control locations within vehicles are systematically related to user acceptability ratings, and (3) there are unique, optimal placement zones for each major category of hand control, such as transmission controls, throttle controls, and hydraulic controls. Furthermore, the models can be used to (1) evaluate current products and (2) evaluate design alternatives for future products.