Johann F. Szautner, PE, P.L.S. ::::
Case Synopsis: A woman was leaving a store in a shopping center on a rainy day and walked to her car parked in the adjacent parking lot. She slipped and fell while walking over a speed bump located across the main access drive. She sustained a broken hip, as well as abrasions to her elbow.
Expert Analysis: Speed bumps are still utilized to force vehicles to slow their speed. While speed bumps can be hazardous to vehicle drivers, they definitely present a classic slip, trip and fall hazard. Their spherical shape is particularly dangerous when stepping on the downward curvature of the speed bump. Forward walking is accomplished by pushing off with the ball of one foot and landing with the heel of the other foot. During forward propulsion, we undergo repeating cycles of stable and unstable equilibrium. The landing heel must encounter sufficient floor friction or our foot slips away. This is even more important when the stepping foot lands on a downward curved surface, as the horizontal component of the tangential friction force will offer less resistance. In this case the speed bump stretched almost entirely from the store side walk to the opposite curb, forcing pedestrians coming from the store to cross it, depending on where they parked their car.
Conclusion: While building codes and site design standards discourage the use of speed bumps as traffic calming devices in areas where pedestrians walk, using a readily available slip resistant coating would have prevented this slip and fall accident. If speed bumps are constructed, warning signs should be placed to alert motorists and pedestrians alike. A typical warning sign would read “CAUTION – SPEED BUMP”. Had such a warning sign been installed, the accident victim would have been warned to proceed with extraordinary caution.Case Studies