Projects of multilane highways are primarily based on the level of service required, but the consequences of such designs in road safety are relevant when compared to two-lane highways, for instance, in which there is a unique lane for each direction. If a central reservation is present, with median barrier or not, the possibility of occurrence of certain types of accidents (such as head-on and angle collisions) are drastically reduced because of the existence of a physical distance or a protection device separating traffic traveling in opposite directions.

However, there are specific cases, in Brazil, where the highways possess two lanes in each direction with a continuous cross-section, in which the separation is only visible due to the centerline, although the Average Daily Traffic (ADT) of these roads may be equivalent to the one in divided highways. The main problem is that, because of both lanes in each direction, drivers are naturally encouraged to develop higher velocities. This similarity between divided and undivided highways, with the only difference regarding the absence of separation, provides an unreal feeling of safety, since the chances of the most fatal types of collision are significantly increased and, with high velocities, the consequences may be even worse.

To investigate the impact of traffic flow separation devices, such as a physical distance, a median barrier or a single centerline, on road safety in Brazilian multilane highways with equivalent average daily traffic, in terms of typology and frequency.

Influence of traffic flow separation devices on road safety in Brazil’s multilane highways