Section 65 of Road Traffic Regulation Act 1984 empowers local authorities to
cause or permit traffic signs to be placed on or near a road
Section 64 defines "traffic signs" as
signs specified by regulations (i.e. The Traffic Signs Regulations and General Directions, currently TSRGD 2016 as amended); or
authorised by the relevant authority (i.e. specially authorised by DfT).
"Prescribed" signs are the first of these: they are prescribed in TSRGD. If you've got a road and it meets certain conditions, Doctor TSRGD will prescribe the appropriate medicine in the form of a traffic sign.
Unlike a physician, TSRGD does not specify the dose: for the vast majority of signs, TSRGD lists various sizes of sign. The highway engineers at the local authority decide which size to use. DfT provides advice in the Chapters of the Traffic Signs Manual (in Appendix A to most Chapters) but local authorities do not need to follow the advice.
For many signs, TSRGD specifies various conditions which must be satisfied for the sign to be used, e.g. that there must be a traffic order whose effects include what the sign is showing. If the conditions aren't present, the sign is not prescribed at that location.
The foundation of our current traffic signs is the Worboys Report of 1963. This set out the following principles:
(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.
Of these, (c) is the principle which some signs fail to achieve. They have become too complicated. Too much information has been crammed onto them, with the result that they cannot be read and assimilated from a moving vehicle.
The following prescribed signs lie behind many PCNs:
["Flying motorcycle"]
Suggestions for how to remedy their defects are put forward in A Tale of Two Cities.
Written 4th November 2025; last updated 4th November 2025