Experimental assessment of safety and comfort of operator's workplace using subjective and objective measurements on two models of tractor

Working with agricultural machines is a hazardous activity. Much has been done to promote safety, but the accidents are still numerous. Studies from human-computer interaction underline the importance of ergonomic considerations for reducing risks and improving safety and comfort in the workplace. As stated by the Directive 2006/42/EC, to reduce the discomfort, fatigue and physical and psychological stress faced by the operator, ergonomic principles need to be considered in designing agriculture machines. Numerous studies have been conducted to evaluate the engineering and biomechanical aspect of safety and comfort of tractor operator's workplace (such as vibration, noise, heat, space available, etc), even though these aspects depend on the overall cabin design, the way the machine is operated and the expectations and sensations of the driver. The paper reports a comparative assessment of safety and comfort of the operator's workplace on two utility 75 kW tractors of different brand. Ergonomic aspects of the tractors cabin were evaluated with regard to operator's perception and feelings of comfort and safety. Groups of novice and experienced subjects in operation of tractors were asked to operate the tractors and perform the most common tasks the machine is designed for. After the operations the subjects were enquired on their feelings about the comfort and safety with regard to the access to the cabin and to the seat, the noise level, the vibration level, the visibility, the perceived safety, the instruments console and the controls (dimension, colours, ease of use, force required, location and arrangement, ease of operating, clearness, etc). A 5 points Likert scale was used and open-ended questions were added at the end of the questionnaire to solicit additional feedback. Measures have been carried out in accordance to specific Standards for some of the investigated features of comfort and safety. Objective data has been compared with results from enquiry on the perceived level of comfort and safety for the same features. Analysis of variance (ANOVA) was applied to quantitative data, while content analysis was used to explore responses to open-ended questions. The assessment pointed out that simple modifications of tractors cabin design (such as size, dimension, position and/or colour of console and/or controls elements) could increase operator's comfort and safety. Design influences the likelihood of human errors. The assessment shows that a better design of instrument console and controls could improve the perceived comfort and safety, and reduce tractor operator effort, work-related injury and fatalities.