Before dealing with the question of lighting short tunnels, it is necessary define what is meant by a tunnel and when it should be called 'short'. Confined to motorized road traffic the following is the most apt definition of a tunnel: every form of roofing-over a road section, irrespective of it length. From the lighting point of view, there is even no objection to applying this definition to a telephone wire stretched across a road and tore to regard it as a tunnel of 1 mm in length. For it will be been that very short tunnels need no lighting at all. It is less simple to define what a 'short' tunnel is. But it is necessary to distinguish very clearly between short and long tunnels. First because such a distinction is already made in normal parlance and in the second place because short tunnels are usually regarded as part of a larger project. In contrast to long tunnels, which are usually treated as a separate, independent project.
Samenvatting