Absence of conflict of interest.
Steiner, L., Burgess-Limerick, R., & Porter, W. (2014). Directional control-response compatibility relationships assessed by physical simulation of an underground bolting machine. Human Factors, 56(2), 384-391. https://doi.org/10.1177/0018720813490953
- The study’s objective was to examine the impact of directional control-response relationships on errors made when controlling roof-bolting machines.
- The study was a randomized controlled trial conducted in a laboratory setting. The authors tested the role of the directional control-response relationships for roof-bolting machines on the amount of selection errors made by participants.
- The study found a significant effect of directional control-response relationships on the proportion of errors made for three of the five levers tested.
- 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 directional control-response relationships for roof-bolting machines, and not to other factors.
Features of the Study
The study used a simulation of a single-boom roof-bolting machine (Fletcher Roof Ranger I) with five levers that are used to control the boom. Four levers (elevation, slew, sump, and stabilizer jack) each move the boom in a different direction, and the last lever (color lever) causes a light to turn on at the end of the boom. The levers were either organized horizontally or vertically. The experiment tested the directional control-response relationship where the participant would move a lever up if horizontally oriented or away from them if vertically oriented (Control-Response Relationship 1 – CRR1). In the second relationship tested, the directional control-response relationship was reversed (Control-Response Relationship 2 – CRR2).
The authors randomly assigned 48 participants to one of four conditions: (1) CRR1 with horizontal levers, (2) CRR1 with vertical levers, (3) CRR2 with horizontal levers, or (4) CRR2 with vertical levers. Each participant completed 6 blocks of 40 trials (240 trials total). The participants viewed a demonstration of the function of the levers prior to the experiment. In each trial, participants viewed a short video clip and had to choose a lever and move it in one of the two directions to replicate what they saw in the video. After each attempt, the bolter arm was moved back to the starting position. Each block lasted approximately 6 minutes, with a one-minute break between blocks.
The outcome measured was the direction errors made by the participants, which were made by moving the lever in the opposite direction. The authors conducted statistical analyses to compare the direction errors for the control-response relationship, lever orientation, and the interaction between the control-response relationship and lever orientation for the five boom levers.
Health and safety
- The study found a significant effect of control-response relationship, lever orientation, and the interaction between the control-response relationship and lever orientation for the boom elevation lever. Specifically, the study found that participants assigned to CRR1 made fewer errors, with less errors found when the boom elevation lever orientation was horizontal rather than vertical.
- The study found a significant effect of the interaction between the control-response relationship and lever orientation for the slew lever. The study found that fewer errors were made when the slew levers were horizontal in CRR1 or vertical in CRR2.
- The study also found a significant effect of the control-response relationship for the sump lever, where participants with vertical levers in CRR2 were the least likely to make errors.
- The study did not find any significant effects of control-response relationship and lever orientation for the color lever or the stabilizer jack lever.
Considerations for Interpreting the Findings
The authors did not explicitly provide information to calculate attrition; however, the experiments were conducted in a laboratory setting, which implies no attrition. The experiment was conducted in a controlled environment, and the authors note that the study results may not generalize to a real-world setting.
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 directional control-response relationships for roof-bolting machines, and not to other factors.