Pedestrian fall incidents are frequently alleged to be caused by a "slippery" walkway surface. Building codes, safety codes, and accessibility regulations require adequate walkway "slip resistance" without specifying how this is to be confirmed. Demonstrating that a walkway surface provides sufficient (or insufficient) traction is a complex task – requiring expertise and (where appropriate) the use of a tribometer for traction measurement. The past five to ten years have seen major advances in the scientific foundations for tribometry, through correlation of tribometer measurements to actual human slip experiences – and this is slowly advancing the "standard of care" for slip-and-fall analyses. The nuances of these scientific foundations are not trivial, however, and the topic has been challenging to understand for both practitioners and laypersons. There have been recent efforts by various standards developers to make pedestrian slip information more useful; the technical robustness of these different efforts varies. It remains to be seen how court decisions will view these various advances, as there are few published court decisions that involve the recent methodologies.
It is important to note that pedestrian slip-and-fall incidents may involve both intrinsic elements related to the pedestrian (medical conditions, medications, activities, attentiveness, etc.) as well as extrinsic elements related to the walkway environment (traction, contaminants, illumination, distractions, etc.).
There are two main types of pedestrian slip events that are routinely studied:
Heel slip: This is the most common cause of a slip-related fall. At the end of the swing phase of the stride, as the leading heel contacts the walkway, the heel slides forward. The momentum of the pedestrian exacerbates the slip, and the leading leg is unable to support its share of the body weight
Toe slip: A toe slip occurs when the trailing foot slips at push off. A toe slip rarely results in a fall, since most body weight has already have been shifted to the leading leg.
