Design and safety issues in lay-bys of road tunnels

Abstract

Lay-bys in road tunnels are built to be used during tunnel operation, both for users in case of emergency and for operating services. According to the specific regulations of each country, after a certain length of the tunnel, among other factors, those lay-bys need to be built at certain distances between them. The geometry of the lay-bys presents differences depending on the different regulations. Some of these regulations are presented in this article. Lay-bys also present some issues that need special attention, like the knowledge of accidents that have occurred in various tunnels due to frontal collisions, more or less offset, of light and heavy vehicles against the facing end of the lay-bys. The solutions to mitigate the effects of such collisions, very often with serious consequences for the occupants of the vehicles, need be addressed through physical testing that can validate the protection systems to be installed in the tunnels.