The goal of Working Group No. 4 is to develop the principles for a safe and cost effective tunnel cross section taking into consideration signalling and traffic management requirements. Due to the costs of tunnels there is a need to minimise their cross section. On the other hand minimum cross sections might cause a decrease of the Free Flow Speed and the Road Capacity, as well as an increase of the chances on Congestion, In- and Accidents, whereas the possibilities for Incident Management and Rescue get less. In 2001 Working Group No. 4 published a report on Cross Section Geometry in Unidirectionel Tunnels, whereas the final draft of a report on Cross Section Design for Bidirectional Tunnels has been submitted in April this year. The goals of both reports are to describe the arguments considered in various countries concerning the dimensions of the cross section that are essential for traffic in terms of safety, capacity and congestion level. It appeared essential to develop a special terminology, of which the main elements will be presented in this paper. The report on one-directional tunnels mainly deals with the cross section, whereas the report on bi-directional tunnels additionally discusses aspects such as longitudinal slopes and radii of curvature. Both reports contain a chapter on the influence of the tunnel-geometry on capacity and speed is treated. All functions of elements of Carriageways, Off-Carriageways (hard shoulders and walkways) and Maintained Headroom are treated, and philosophies behind the various guidelines are described. Both report will provide designers and decision makers with arguments for cost-effective designs. For the covering abstract see ITRD E135448.
Samenvatting