Simply but, if the human is to exchange the energy over a small point of contact with an object of greater density, the human will exchange her or his energy over a short time and short space. Exchanging energy over a short time and space will produce significant loss to the human. Research indicates that if the head of a human makes contact with a solid object, at a speed over 2 mph, the force generated is sufficient to crack the human skull open. To effectively deal with slips, trips, and falls, countermeasures must be developed that address prevention, severity reduction, and cleanup. The role of any given prevention countermeasure is to reduce the probability that a trip or slip will take place.
Stairs represent a change in walking conditions for humans.
By maintaining even spacing between risers and keeping the rungs, at the appropriate length, the probability of a human tripping on them is significantly reduced. Another prevention approach would be the act of cleaning up a spill on the floor and posting warning signs to alert people that the floor is wet. This approach is intended to reduce the probability of someone slipping. Severity reduction countermeasure, unlike prevention countermeasures, are intended to reduce the loss associated with the energy exchange that follows falls. Since stairs represent a change in walking conditions for humans, the chance of tripping is increased.