The SpeedLimit Guide to Speed Limit Setting
Note: These are my personal views, drawn from extensive experience of driving and using the roads as a pedestrian, advanced training and study of official documents on speed limit setting. They are not a statement of official government policy, or the policy of the ABD, IAM or any other body. The current standard UK speed limits are set out in Rule 103 of the Highway Code.
80 - this should be the limit on open country sections of motorway with well-spaced junctions. It could also be used on well-aligned non-motorway dual-carriageway trunk roads with grade-separated junctions, where there are access restrictions to exclude pedestrians, cyclists and agricultural vehicles. I don't personally advocate totally derestricted motorways on the German model: in my view 80 mph, enforced with a reasonable degree of latitude, is the best compromise between utility and safety. This approximates to the 130 kph (81 mph) limit that applies to motorways in most Continental countries.
70 - this should be the default National Speed Limit outside urban areas for both single and dual carriageway roads (currently 60 for single-carriageway roads). It should also be used (as at present) for motorways in more urban areas with closely spaced junctions, tight bends and much weaving traffic. I would see, for example, all of the M60 retaining a 70 mph limit.
60, 50 - these limits should be used sparingly in rural areas for locations where there is heavy traffic and specific, identifiable hazards that justify a reduction from a default speed of 70. They should not be applied to long continuous stretches of rural main road. Currently sub-NSL rural limits are imposed far too freely. 50 can be used for scattered settlements where development is not dense enough to justify a 40 limit, but some extra caution is needed. 50 is also appropriate for some grade-separated urban dual carriageways with tight bends and junctions.
40 - this should be used on suburban main roads which are wide, have good sightlines and are not heavily developed on both sides. It is also appropriate for roads on the fringes of urban areas which are only built up on one side, or where there is substantial but not continuous development, and for main roads through villages with similar development patterns.
30 - this is, and should be, the default speed limit in urban areas. It is appropriate for shopping streets, minor residential roads and main roads with dense development on both sides. It has however been applied to many suburban main roads where a 40 limit would be more appropriate. It can also be applied to small rural villages where it is in effect self-enforcing. Main roads through villages should only be given this limit where the road is closely built up on both sides and there is a significant presence of pedestrians.
20 - this may used as an advisory limit only in limited circumstances for locations where severely restricted visibility or very large numbers of pedestrians prevent safe progress at a higher speed, for example in areas of Victorian terraced housing with narrow streets and many parked cars, and the centres of historic towns. It should not be used indiscriminately on more modern housing estates with good road alignment and sight lines. In these locations, unless backed up by physical traffic calming measures, compliance is likely to be low.
The current official criteria for speed limit setting contained in Department for Transport Circular Roads 1/06, which contains plenty of encouragement for local authorities to reduce limits, can be downloaded here.
The previous official criteria contained in Department of Transport Circular Roads 1/93, which unfortunately were widely ignored by anti-car local authorities, are here. Unfortunately these have now been removed from the DfT website. here
There is also a page putting across a similar message to this one on the Speedcam.co.uk website (follow the link to "Speed Limits" from the main page)
(Last updated October 2006)