London, 20 Nov 2001.
For immediate release.

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Press Release

Speed Limit Signs, Clarity and Safety
The ABD is today calling for the government to re-think its policies on setting and signing speed limits.
The ABD's Chairman, Brian Gregory said
"I am hearing of more and more cases where drivers are prosecuted for exceeding 30 mph limits on roads where they genuinely had no idea that the limit was 30. The increasing lack of uniformity in the setting of limits and the abysmal level of signing leaves drivers guessing what the limit actually is. We certainly don't condone law breaking or inappropriate speeds, but we believe that many speeding offences are a result of poor signing, not a deliberate wish to break the law. In some areas more responsible Local Authorities are erecting 'This is still a 30 Zone' signs as a way of reducing speeds and getting round restrictive guidelines on the use of repeaters. Others just erect a 'safety' camera."

The ABD's Road Safety Spokesman, Mark McArthur-Christie said

"Some drivers drive like idiots and need their speed curbing, but we believe that the vast majority of drivers would stick to speed limits if they were more clearly posted, or councils put up repeaters where the environment changes."

Speed limit signs, clarity and safety

All forms of travel have always been subject to rules and regulations in the name of safety. Some are simple to understand. Others are increasingly difficult to assimilate, and it is this increasing difficulty this paper addresses.

Over the years an acceptable and understandable hierarchy of speed limits developed, formalised by Annex A to Circular Roads 1/93.

This basic hierarchy was subject to fine tuning. This tuning was achieved by assuming that the vast majority of motorists have a sense of social conscience and self-preservation and will adjust their speed to that suitable for the road. The 85th percentile speed of drivers was used to make a final decision as to the suitable speed limit. Hazards that present a danger at the posted limit were highlighted with warning signs. This system was nationally adopted, understandable by all, and resulted in some of the safest roads in the world.

Due to the manpower and technology available, enforcement tended to be limited to times and places where excessive speed presented an identifiable danger to public safety. At this level of enforcement limits served the safety intentions of the speed laws and were widely acceptable.

Over recent years, with central government devolving responsibility to local authorities, the understood reasoning behind speed limits has been allowed to slip, leading to an area-by-area difference in the standards by which limits are set and enforced. Against this background has come an increasing technological ability for absolute detection and enforcement.

Unfortunately for the road user, the present rules on posting speed limits do not always make the legally acceptable speed obvious. The biggest problem appears to be in 30 mph areas.

When 30 limits were first introduced they were for urban areas. At the time street lighting was mostly restricted to residential areas, and the presence of lighting was a good guide as to areas suitable for a 30 limit. It became understood in law that street lighting indicated a 30 limit unless indicated otherwise.

Nowadays street lighting can be found on motorways, by-passes, ring roads and many other sites miles from any habitation. Some Local Authorities use the presence of street lights as an excuse not to maintain the proper signing of the beginning of a 30 limit, because 'the law says that lighting means a 30 limit'.

While a 30 limit indicates hazards that should merit street lighting, it is no longer the case that street lighting automatically indicates a 30 limit, and the link should be severed.

When 30 limits were introduced urban areas were generally smaller. This, together with the presence of lighting, meant that 30 limits were generally for comparatively short, identifiable, distances. The decision was taken, quite reasonably, that repeater signs were not necessary.

Over the years residential areas have increased considerably in size and it has become possible to travel some miles, limited to 30 mph, and never see a sign. So long as the guidelines of 'built up area equals 30 mph' were followed it was possible to judge the correct speed, particularly with the aid of the limit start and finish signs.

However, there is a growing trend in some areas to reduce speeds between residential areas and extend 30mph limits beyond them. Often a legitimately-set NSL is reduced to 30 mph by the simple (and cheap) expedient of removing the de-restriction signs and repeaters.

This can result in road users travelling many miles, along roads that can vary from densely residential to open country or even dual carriageway with no indication of, or change in, the legal speed limit.

The lack of change of limit removes the demarcation of 'hazardous' residential areas that drivers have always used as a base for their perception of the degree of care needed. It also appears to lead to an increase in speed in some residential areas, mostly because drivers have judged that the non residential stretch is NSL and have not seen a speed reduction sign.

The best solution would be to join 'high risk' residential areas with limits of at least 40 mph, allowing 30 mph demarcations where the nature of the road changes, and repeater signs on the joining stretch.

Consideration should be given to easing the guidelines on '30' repeaters to allow, or even require, their siting at points where excessive speed is an identified problem. It may simply be due to an unclear limit, where the general characteristics and level of development of the road are such that a driver would not in general expect the road to be subject to a 30 mph limit. This problem should be treatable without adding to the projected millions of speeding convictions.

The problem with driver confusion over speed limits on unsigned 'joining' stretches is not helped by some Local Authorities reluctance to maintain de-restriction signs. At least one LA's response to a query about the limit on a road was 'It's de-restricted but we don't want to tell people that'!

An increasing number of road works, while being heavily enforced with cameras and unmarked police vehicles, do not bother with de-restriction signs at the end of the limit, instead relying on the 'road works end' sign. This can lead to a dangerously high speed differential between locals who know the limit has ended and visitors to the area who continue at the lower speed, unsure whether the limit extends to further road works.

Both of these practices present great difficulties for drivers seeking to drive safely and comply with posted limits. All limits should be clearly posted at both the beginning and end.


The growing ability for absolute enforcement of the speeding laws, together with changes in the ways they are set is bringing about a need for a new look at the signing of speed limits.

The rule that street lights mean a default 30 should be dropped, although a 30 limit should mean that there has to be street lights. 30 repeaters, either signs or roundels on the road surface, should be permitted, and even required as a treatment for excessive speed where suitable as an alternative to a camera.

Repeaters are necessary to help the driver differentiate between types of road environment. This should preferably be by a change in speed limit. Where this is not considered appropriate a gateway treatment should be strongly recommended.

All limits should be clearly signed at the beginning and end, and repeaters or roundels used as an emphasis and reminder at suitable intervals.

Limits should be set to a reasonable and logical national standard, preferably retaining Circular Roads 1/93, and not allowed to vary between local authorities.


Notes for Editors