on our roads has been happily reduced in relation to the number of vehicles using them, it is still horrifyingly high and every possible contribution must be made by traffic signs, as by every other means, to reduce accidents.
25. The first objective must therefore be to obtain the greatest possible effective ness of traffic signs. The necessary impact upon drivers could be achieved by the use of glaring colours or great size. This would be aesthetically offensive as well as costly. The problem is therefore to take into account continuously the three factors of functional efficiency, aesthetic acceptability and expense . At every stage in the design of traffic signs and in the development of a comprehensive traffic sign system, the increased cost of a higher standard of sign must be balanced against the greater safety resulting and both must be assessed as accurately as possible in relation to amenity before recommendations can be made. We have been very fortunate in the assistance we have received from the Road Research Laboratory in the many tests and experiments which they have carried out to determine the relative efficacy of various aspects of traffic signs.
26. In considering first how the greatest efficiency of traffic signs should be achieved we believe the following general principles are the most important:—
(a) the signs must be designed for the foreseeable traffic conditions and speeds on the roads on which they are to be used;
(b) they should be conspicuous so that they will attract the attention of drivers at a sufficient distance and should be easily recognisable as traffic signs at that distance;
(c) they should contain only essential information and their significance should be clear at a glance so that the driver's attention is not distracted from the task of driving;
(d) they should be legible from sufficiently far away to be read without diverting the gaze through too great an angle;
(e) they should be placed so that they are obscured as little as possible by vehicles and other objects;
(f) they should be designed and sited so that after reading the sign the driver is left with sufficient time to take any necessary action with safety; and
(g) they should be effective both by night and day.
The critical factors in meeting these requirements are shape, colour, layout and size of sign, the size and kind of the symbols and lettering on it, its position and its illumination or reflectorisation .
27. In considering how far existing signs met these requirements and in what ways they fell short of them, we took into account the criticisms which had been voiced in Parliament, in the press and by other means. We also sought advice from the organisations most closely concerned with traffic signs. A list of these is given in Appendix I and we are grateful to them for the careful study which they gave to the subject and for the comments and constructive criticism which we received from them. We were assisted very greatly by the work done on the
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