Expressed in millions the numbers of passengers carried by the various forms of transport in London have been estimated as follows tools for breaking up old foundations. In the busiest thorough fares repairs should proceed uninterruptedly day and night. Co ordination between adjoining highway authorities would prevent the annoyance of parallel routes being simultaneously closed for repair. The extreme need of some co-ordinating body for London led to the creation in 1924 of the London and Home Counties Traffic Advisory Committee, which reports to the Minister of Transport upon all matters affecting transit in that populous area. High-level Roads.—To relieve the congestion at the ground level of great cities the construction of high-level roads may before long be forced upon civic authorities.
Narrow streets which are so situated as to form useful lines of communication can often be advan tageously utilized as single-way routes, a practice which has been widely adopted in Paris, where no less than 105 streets are re served for one-way traffic. In London this restriction has been applied to 45 streets. Obviously the facilities for establishing alternative routes and single-way routes are greatest in cities which have been methodically laid out on a fairly rectangular plan. In cities of haphazard growth more formidable difficulties arise. The delay inflicted upon traffic at busy cross roads can be eliminated by the enforcement of gyratory movement in the rare cases where space permits, or by the construction of a bridge or tunnel enabling one stream of traffic to pass over the other—a device that is only rendered feasible by a convenient configuration of the ground. The ample dimensions of the "places" of Paris have enabled gyratory movement to be instituted at 19 traffic centres, whereas in London the experiment was tried in Jan. 1926, for the first time, in Aldwych and Parliament Square where its success has led to its extension to i o other traffic centres. (See figure illustrating the arrangement prescribed for Trafalgar Square.) At 14 important road intersections where space for gyratory movement is lacking the regulation is imposed that vehicles shall not turn to the right. By this means the steady flow of traffic is promoted.
White lines formed by metal plates sunk into the pavement or by similar devices play an invaluable part in directing traffic into its proper channels. The acceleration of vehicular traffic due
to the adoption of these various methods of control renders it necessary to indicate special crossing places for pedestrians. In great cities the construction of subways or bridges for foot passengers is likely to be increasingly favoured where funds permit.
An experimental installation of light signals was brought into use in London at the junction of St. James's Street and Piccadilly in 1926. These signals, eight in number, are electrically operated from a central control at the junction of the two streets. They are of the three-aspect colour-light type, fitted with red, amber, and green lenses, with the necessary trans formers, and are mounted on tubular steel posts on cast iron bases. Five of the signals are fitted with a small lens which serves as an indication to the constable on point duty that the signal is showing red. The central control cabin is equipped with an illumi nated diagram which repeats all signal aspects and with a minia ture frame of eight levers, space being provided for the addition of a king lever, if necessary. Each of the levers has three posi tions—normal, mid-stroke and reverse—providing red, amber and green indications, respectively.
Whatever efforts may be made to take full advantage of the roads already in use, the vast increase in vehicular traffic will in most of our growing cities call for the provision of additional thoroughfares. While the radial roads may be tolerably adequate it will usually be found that suitable cir cumferential roads are wanting, save in the case of towns whose fortifications have given place to a ring road. Relief to the con gested centre of a city can often be most readily afforded by the building of circular roads which enable traffic to pass round the outskirts. By suitable regulations it should then be possible to limit the passage through the crowded centre to vehicles whose business legitimately requires their presence there. Little hardship is inflicted upon drivers who are relegated to the circular road, seeing that, although their journey may be longer, the time occupied is less, owing to the absence of congestion. As a good example of this type of route may be cited the circular road, 26 m. long, round the north of London.