Rampway Safety: Foot Forces as a Function of Rampway Angle

The objective of this study was to determine the effect of rampway angle on forces at the shoe/floor interface. Force plate measurements were taken on normal subjects (18–28years) while walking up and down a rampway at angles from 0 to 20° in 4°-intervals. Shear forces and forces normal to the surface were collected. These data then were used to estimate the required coefficient of friction (RCOF) by dividing the shear forces by the normal forces over time. Peak RCOFs were identified from each trial. Step lengths and walking speed also were recorded. Regression analysis showed a significant linear relationship between peak RCOF and rampway angle. Peak RCOF ranged from 0.15 for a flat surface to over 0.6 for a 20° incline and was consistently higher for walking upwards. Foot force analysis showed that for downward walking, shear forces increased on initial contact and remained elevated through longer portions of the step as the ramp angle increased. This suggests that slips at heelstrikes are of particular concern on inclined surfaces due to increased shear force levels that continue through the midstance phase of a slip. The results—although from a small population consisting of normal, young adults—indicate that the use of steep ramps in the workplace may require significant slip-resistance characteristics to prevent fall injuries.