  Conditions for the occurrence of bidirectional collisions are developed based
on the Simon-Gutowitz bidirectional traffic model. Three types of dangerous
situations can occur in this model. We analyze those corresponding to head-on
collision, rear-end collision and lane-changing collision. Using Monte Carlo
simulations, we compute the probability of the occurrence of these collisions
for different values of the oncoming cars density. It is found that the risk of
collisions is important when the density of cars in one lane is small and that
of the other lane is high enough. The influence of different proportions of
heavy vehicles is also studied. We found that heavy vehicles cause an important
reduction of traffic flow on the home lane and provoke an increase of the risk
of car accident.
