Are Drivers with Small Feet or Long Legs at Greater Risk of Rear end Collisions?

Abstract

Drivers generally respond to imminent lead vehicle collisions with a rapid foot movement from the gas to the brake pedal. During the transition time from gas to brake pedal the vehicle essentially continues its current speed as the remaining distance to the lead vehicle rapidly decreases. It is therefore critical to understand the mechanisms of foot movement during this transition period and determine if individual differences can effect transition time. We provide support for the hypothesis that transition times are longer for some drivers due to difference in their default foot and leg positioning and concomitant foot movement strategy. It is hypothesized that people with small feet are most constrained in their heel positioning especially in cars with wide pedal separation and that they cannot achieve the same rapid transition time associated with a simple rotation around the heel that people with larger feet can. It is also be hypothesized that taller people are in some cars constrained into a diagonal foot with a bent leg position that forces them to also move their entire leg in order to quickly depress the brake pedal. The difference between these foot plus leg movement strategies compared to simple toe swing around a fixed heel is on the order of 50–100ms which in critical situations can easily mean the difference between avoiding a crash and having an impact velocity of 5m/s.