Specific hazards in road tunnels

The tunnel environment influences the hazards of road traffic in a specific way:

• on the one hand the confined space of a tunnel provides protection against various influences which may cause incidents (e.g. weather conditions), thus reducing the frequency of various types of incidents
• on the other hand the confined space increases the consequences of collisions and in particular the consequences of fires and limits the accessibility to the site of incident, thus impeding self-rescue as well as assistance by rescue services

Hence in tunnels there is a trend towards less frequent, but (much) more severe incidents.

Tunnel safety studies typically focus on significant incidents, which have the potential to develop into events with serious consequences, mainly with collisions and fires. Furthermore, the manifold hazards potentially caused by dangerous goods require special attention. As an unrestricted availability of underground traffic infrastructure is crucial  for economy as well as mobility, in particular on major transport axis and in areas with high traffic loads like big cities, events potentially causing significant traffic interruptions are additionally put into the center of attention. In this context security aspects have been gaining importance in the recent years.

Alternative propulsion technologies, including battery-electric vehicles, are becoming more prevalent. Whilst such vehicles remain a small overall proportion of the vehicle fleet, the combination of impacts of Government policy and technological advances in alternative fuels is expected to accelerate their increase in numbers on the road and in tunnels in coming years. The technical report Impact of New Propulsion Technologies on Road Tunnel Operations and Safety - Literature review reflects investigations carried out.