Abstract
IN a paper read before the Institution of Railway Signal Engineers by F. Edwards, an abstract of which appears in Roads and Road Construction for July 1, the development of systems of road signalling is doscribod. There are two main developments which may be regarded as milestones in the progress of street traffic signalling. The first system is time-controlled and, thanks to the specification issued by the British Standards Institution, it works fairly woll. Up to the end of February of this year, grants had been issued for the erection of signals at more than 1,700 crossings in Britain, and naturally the installation of all these crossings is costly. The second step in advance was the introduction of the vehicle-actuated method of control, which has several advantages over the time-controlled system. With the time-controlled apparatus the ‘right of way’ is given to each of two or more intersecting roads for definite periods of timo in sequence, quite regardless of the relative volume of traffic on the roads at any particular moment. One of the essentials of any form of control is to keep traffic moving, and this should only bo subordinate to safety. The time-controlled system is powerless to differentiate between the volumes of the flow of traffic in the various directions. Many attempts were made in the past to produce a system which would provide maximum traffic facilities with maximum safety. There are now two systems of vehicle-activated control in praotice, called the electromatic and the autoflex respectively. In the former, a vehicle passing over a pad makes contact and completes an electric circuit; in the latter the air in a channel in a rubber moulding is compressed and the compressed air produces the contact. The problem of co-ordinating a series of crossings is now being satisfactorily solved. Oxford Street, London, from Marble Arch to Tottenham Court Road is a good example of the advantages of this kind of control.
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Traffic-actuated Road Signals. Nature 136, 253–254 (1935). https://doi.org/10.1038/136253c0
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DOI: https://doi.org/10.1038/136253c0