The Walker-Bicycle Response Law

In the months of experience i have riding a bicycle through a crowd of people, I have created a law that determines how a walker will behave when a bicycle approaches them. Here is what it states:

Let vb and vw be the velocities of the bicyclist and the walker with respect to the ground, A the angle between them, and R the distance between them. Then the probability that the walker will begin to exhibit Brownian motion is given by
PB = 0 for A <>
PB = e^(-kR) vb vw for 180 > A > 90
for some constant k. A corallary of this law is that the probability that an accident will occur between increases with PB. So, for God's sake, walk in a PREDICTABLE straight line.