SOME ASPECTS OF OPERATIONAL DESIGN OF MAJOR BRIDGES AND TUNNELS

This paper discusses the justification of special facilities which may be based on various factors, including higher design loadings, restrictions on width and clearances, absence of hard shoulders, operational constraints on vehicles permitted, operational and maintenance needs, environmental conditions, and the presence or lack of alternative routes. Legislative considerations are also presented. The factors to be considered include whether a separate operating authority is proposed, whether weight or height restrictions are necessary, and whether any classes of vehicle are to be prohibited. The need for various system elements are dealt with in turn, main items being surveillance, environmental detection, incident detection, height or weight detection, and the various elements making up the control system. Equipment and level of provision is studied. This includes; closed-circuit television, telephones, radio, incident detection loops, wind, fog and frost detectors, height gauges, weighbridges, traffic signals, lane control signals, variable-message signs, road lights. The level of control processing will depend on the size of the installation and whether it is free-standing or part of a wider system. Some ways in which the equipment can be used will be described. (TRRL)