Evaluation of a force plate system for measuring center of pressure in railroad ballast

- We evaluate a force plate system for measuring center of pressure in railroad ballast.
- The effects of surface conditions (NB, WB and MB) were not significant for ΔCOPx, y, z.
- No difference was found for ΔCOPx, y, z between level and cross-slope conditions.
- ΔCOPx, y, z were different between the center and corners of force plate in ballasts.
- This force plate system can expand the scope of biomechanical studies on ballast.

Traditional biomechanical analyses have focused primarily on the human gait across hard, flat surfaces and provide little information about human locomotion as a function of work environment or terrain. The purpose of this study was evaluation of a force plate system for measure of center of pressure (COP) in railroad ballast by comparing its accuracy across three surface conditions (hard surface, mainline ballast and walking ballast) with two configurations (level and 7° cross-slope). Custom walkways and an isolation fixture were developed to rigidly attach a force plate beneath ballast surfaces to collect the COP. The difference in COP location (ΔCOPx, y, z) between the force plate system and a calibration system (motion capture derived) were compared using repeated-measures analysis of variance. Results indicate that the effects of surface condition and configuration were not significant for ΔCOPx, y, z and no differences were found among the three surface conditions during pairwise comparison, though ΔCOPx, y, z were different between the center and corners of the force plate in ballasts for both level and cross-slope configurations. The system presented in this study demonstrates the feasibility of measuring the COP by using an isolation-fixture force plate to expand the scope of biomechanical studies on ballast surfaces that are level or cross-slope.