The aim of this paper is to study the contribution of intervehicle communication (IVC) to reduce the number of secondary collisions caused by an accident. We assess the impact of broadcast protocols used to disseminate warning messages and the impact of IVC penetration ratio on the number of collisions. There are two main contributions in this paper. First, it addresses the analytical evaluation of broadcast protocols in Vehicular Ad hoc NETworks (VANETs). We propose a general framework based on point processes to evaluate the performance of this protocol. Our approach is based on the theory of point processes and Palm calculus. We derive, for a generic frame error rate (FER) function, simple formulas for computing the delay required to propagate messages. These formulas hold for any FER function, enabling the comparison of broadcast performance under different radio propagation environments. In the second part of this paper, we propose an analytical evaluation of the number of vehicles involved in a collision. This analysis allows us to study the impact of radio technology penetration ratio and the impact of safety message delivery delays on the number of collisions.