What is Critical Visibility

The construction of road tunnels is an important part of road infrastructure. The operation of road tunnels has historically been accompanied by a number of extraordinary events. Fires are among the most dangerous ones. Individual countries create their own safety standards that mutually differ to a large extent. Some of the differences of the requirements for safety devices, including the requirements for their functionality, are compared and commented on in this chapter. Moreover, attention is paid to the use of asphalt surfaces on roads and sidewalks in tunnels. This chapter also describes the approach to fire ventilation in tunnels, one of the most significant safety devices. Special attention is paid to the choice of the strategy of longitudinal ventilation, which has been the subject of many discussions. This chapter outlines the possible directions for a solution in the future.