Absence of conflict of interest.
Burgess-Limerick, R., Zupanc, C., & Wallis, G. (2013). Effect of control order on steering a simulated underground coal shuttle car. Applied Ergonomics, 44(2), 225-229. https://doi.org/10.1016/j.apergo.2012.07.007
- The study’s objective was to examine the impact of first-order and second-order joystick controls on mining shuttle car steering accuracy over multiple trials.
- The study was a randomized controlled trial conducted in a laboratory setting. The authors compared the steering accuracy of mining shuttle car operators when the operators were using a first-order versus second-order joystick steering mechanism and how the accuracy varied with repeated trials.
- The study found that the operators using the first-order joystick control had significantly better steering accuracy than those using the second-order joystick control. Both groups significantly improved over the three trials and the difference in the performance of the two groups lessened over the three trials.
- The quality of causal evidence presented in this report is high because it was based on a well-implemented randomized controlled trial. This means we are confident that the estimated effects are attributable to the joystick mechanism, and not to other factors.
Features of the Study
The study was a laboratory experiment conducted at the University of Queensland in Australia. The authors used computer simulations to test the operator steering accuracy of underground coal mine shuttle cars using two types of joystick controls. First-order joystick controls are comparable to conventional steering wheels, with constant displacement of the steering device causing a constant rate of change of vehicle heading. Second-order joystick controls introduce acceleration control making it more complex than first-order control and requiring the operator to make more joystick movements to execute the same operations.
The authors randomly assigned 24 participants—with no experience operating mining shuttle cars—to either the first-order or the second-order joystick group. Using a desktop simulation platform, the participants steered a mining shuttle car traveling through a computer simulated underground mine. To establish that the two groups had similar aptitude, participants completed a five-minute familiarization phase. The participants, with an overhead view of the course, used a conventional steering wheel to navigate the simulated mine. Next, they navigated the 14-minute course with the first-person view using the steering wheel. Participants then completed three 14-minute trials using their assigned treatment joystick (12 participants for first-order and 12 participants for second-order). The outcome measured was the time the vehicle was in contact with simulated mine wall with lower times representing superior steering accuracy. The authors conducted statistical analyses to compare the outcomes for the first-order joystick operators and the second-order joystick operators, the performance of each group over three timed trials, and the interaction between the type of joystick and repeated performance.
Health and safety
- The study found that steering accuracy was significantly better for the group using first-order joystick controls compared to the group using second-order joystick controls.
- The study also found that steering accuracy significantly increased with each trial for both the first and second-order groups and the differences between the groups decreased over each trial.
Considerations for Interpreting the Findings
The authors compared the outcomes of participants using the first-order joystick control and the second-order joystick control over the course of three trials with one measure of a pre-intervention driving skills to establish that the randomly selected participants were of equal driving ability before the trials. The authors raise the possibility that the initial trial using the steering wheel may have had more of an improvement effect for first-order joystick operators but this concern is generally dismissed since all participants were familiar with steering wheel operations before the trial. The sample size for the study was small and attrition was not explicitly stated; however, the laboratory setting implies there was no attrition.
Causal Evidence Rating
The quality of causal evidence presented in this report is high because it was based on a well-implemented randomized controlled trial. This means we are confident that the estimated effects are attributable to the joystick mechanism, and not to other factors.