TY  - JOUR
PY  - 2009//
TI  - What is 30?
JO  - Collision: the international compendium for crash research
A1  - Simpson, Lenny
A1  - Russell, Greg
SP  - 26
EP  - 29
VL  - 4
IS  - 2
N2  - The "slide to a stop" equation can be used to calculate the speed of a vehicle. In this equation, speed equals the square root of the total of 30 multiplied by the distance of the tire skid marks multiplied by the deceleration factor (S=√30Df). This article explains how the "30" is derived in this equation. The 30 is not simply a math constant. The value of 30 functions as a conversion factor which contains the value of gravity and the constant 2. Any time 30 appears in an equation, it retains the units of square miles per foot per square hour, and the units for the velocity variable in the equation will be in units of miles per hour.<p /> 
LA  - 
SN  - 1934-8681
UR  - http://dx.doi.org/
ID  - ref1
ER  -