A Comparative Risk Assessment of Remote Control Locomotive Operations versus Conventional Yard Switching Operations

This study involved a comparative risk assessment of U.S. remote control locomotive (RCL) and conventional yard switching operations. First, a hierarchical task analysis provided a description of yard switching tasks. Based on the task analysis, a preliminary hazard analysis and human reliability assessment were performed. For each method of operation, the preliminary hazard analysis identified a worst credible scenario for 19 potential outcomes. Each scenario was assigned a risk score based on an assessment of the likelihood of occurrence and potential severity. The human reliability assessment consisted of two, complementary techniques: The Human Error Assessment and Reduction Technique (HEART) and Absolute Probability Judgment (APJ). A set of yard operating scenarios was developed to provide the basis for the HEART and APJ assessments. Analysis of preliminary hazard analysis variables indicated that the 19 RCL worst credible scenarios yielded a higher total risk score compared to 19 similar conventional worst credible scenarios. The HEART assessment did not reveal any differences between the two methods of operation in terms of human error probabilities (HEP); however, substantial variability existed in HEP assignments between assessors, suggesting that HEART may be inappropriate as a human reliability assessment technique for the railroad yard-switching environment. The APJ data show a trend toward greater HEP for RCL scenarios, although individual HEP values varied across a large range. The HEART and APJ results should be considered preliminary and interpreted with caution due to their subjective nature and the numerous study limitations and methodological challenges.