In addition to the basic cross-section and alignment geometry required for traffic operations, special facilities are provided in most road tunnels to cater for the particular operational and safety demands of the tunnel environment.
Emergency exits are provided in all except the shortest tunnels to allow tunnel users to evacuate on foot from the traffic tube to a place of safety.The different types of emergency exits for pedestrians are considered in Section Emergency exits. These include cross-connections and cross-passages between tubes, refuges where the public can remain safely during an emergency, and safety galleries (passages) constructed alongside the traffic tubes or perhaps under the carriageway and leading to the surface.
Section Facilities for vehicles considers the facilities provided for vehicles.These include lay-bys, turning bays and cross-connections between tubes for vehicles.These cater for situations such as vehicle breakdowns or to allow vehicles to turn around or cross into an adjacent tube, which could be useful for maintenance, for manoeuvring emergency vehicles during an incident, or for traffic management following an incident.
Section Safety recesses considers the geometrical aspects of safety recesses, which may be provided at intervals along the walls of a tunnel, to allow the occupants of a broken down vehicle to move away from the carriageway and minimise the risk of being struck by moving traffic.
Drainage is important to minimise the size of pools that may otherwise form in the event of a spillage from a road tanker or during routine wall washing. In the event of a spillage of flammable liquid, the drainage system can have a major effect on the size of a resulting fire. Section Tunnel drainage considers the different types of drainage systems provided in road tunnels.
Section Other facilities describes other facilities that may be provided within or at the portals of a tunnel.
This Chapter was written by Robin Hall (UK).