Fabulous Forties

The rise and fall of the suburban 40 mph speed limit


Some 40 mph limits still survive on high-quality urban roads - but for how much longer?

In 1935, after five years of having completely derestricted roads for cars and motorcycles, the British government introduced a 30 mph speed limit in built-up areas. The decision was taken to define built-up areas as those having continuous street lighting. Once you had passed a 30 mph sign, the presence of street lights continued to denote a 30 mph limit, without any need for reminder signs, until you reached the derestriction signs at the other side of the town. At the time represented a reasonable correlation, as street lighting rarely extended very far outside urban zones.

It was recognised at the time that there were some major arterial roads with street lights where a 30 mph limit was not appropriate, and the law allowed for "destriction" repeaters to be placed on lit roads where the speed limit did not apply these are shown in contemporary editions of the Highway Code. For over twenty years, 30 mph remained the only road speed limit in the British Isles (apart, perhaps, from special limits applying to some tunnels and bridges).

In 1935, towns were much smaller and more compact than they are now, and the areas covered by the new 30 mph limits were not in general very large. But the urban landscape was already changing, with large areas of new housing being constructed, both council and privately-owned, generally to much lower densities than before and served by wide, straight new roads, often dual-carriageways, which before the mid-1920s had been unknown in Britain. In cities such as Birmingham, Manchester and Liverpool, tram tracks were often laid in the central reservation.

This trend continued after the war, and by the mid-1950s British towns and cities were much larger and more sprawling than they had been thirty years earlier. The new suburbs were served by main roads of much higher standard than the old urban streets, and it was clear that, while the speed limit on these roads remained at 30 mph, speeds of around 40 mph were commonplace without any particular safety problem.

Rather than make futile attempts to enforce obviously inappropriate 30 limits, the government of the day decided to recognise the situation by introducing a new speed limit of 40 mph. This was specifically intended for these high-quality outer-suburban roads, although clearly it could also be applied to other roads with similar characteristics, which had too many houses near them to be suitable for derestriction, but were obviously of a higher standard than the traditional urban streets for which the 30 mph limit had been intended. I have not been able to find out the exact date when 40 mph limits were introduced but I believe it was around 1957.

Implementation of the new limit was left to the discretion of local highway authorities. At a time when the motor car was seen as a symbol of progress and there was little of the current anti-car sentiment, most were keen to make use of it, although inevitably there were some slight differences in interpretation.

Probably the most characteristic application was on major radial and orbital dual carriageways. Good examples of this are Kingsway and Princess Road in Manchester, Bristol Road in Birmingham and many roads in Liverpool such as Menlove Avenue, Queen's Drive and Walton Hall Avenue, although such roads can be found in virtually all large cities. The very similar A82 Great Western Road in Glasgow currently has a 30 limit if this has applied continuously since the 1950s it marks a distinctly different interpretation.


A classic 40 limit on an outer-suburban dual carriageway, the B4121 at Northfield, Birmingham

Application of 40 limits to single-carriageway roads was more patchy. Birmingham, for example, while it made extensive use of 40 limits on dual carriageways, did not have any single-carriageway 40s before its boundaries were extended to include Sutton Coldfield in 1974. Manchester, in contrast, had a more flexible policy and had a number of single-carriageway 40s (most of which in fact have now been converted back to 30s). The widespread application of 40 limits to dual carriageways gave rise to the widely-held but always erroneous belief that the default speed limit on a lit, urban dual carriageway was 40, not 30.

Outside the big cities, many county councils introduced 40 mph limits on main roads on the approaches to towns where the development was lighter something that until recently could still be often seen in Cheshire and Warwickshire, for example. The mileage of 40s has recently been much reduced by speed limit cuts, but in most parts of the country it is still possible to see them once the terraces give way to semis, the road opens out and grass verges and parks appear.

The police generally welcomed the new limits, as they removed a restriction that was widely seen as unreasonable and outdated, and that gave them problems with enforcement. The initial verdict was very positive, with no significant safety problems being reported, and in most cases actual speeds showing only a slight increase or even falling, perhaps because drivers were more likely to adhere to a limit they perceived as reasonable.

For example, a Department of Transport report stated: "A before and after study carried out at 20 locations through Kent, where the limit had been raised from 30 mph to 40 mph, showed a fall in speed, or no change, in 80% of the measurements taken, and a small increase in the others. The total number of accidents fell by almost 20%."

More details can be found on this page on the ABD website.

After the initial wave the pace of conversions from 30 to 40 inevitably slowed, but it continued to happen throughout the 1960s and 1970s until the 1973 oil crisis. It was also taken as read that new high-quality urban roads would be given 40 mph limits for example the western half of the A34 Newcastle-under-Lyme inner ring road, which is a dual carriageway with at-grade roundabouts in a very urban setting, and the unclassified Belmont Way in Stockport which I believe opened in the late 1970s (see photo at the top of the page).

After the oil crisis there seem to have been far fewer examples of roads having their speed limits increased to 40 mph, but it may simply have been the case that most of the obvious candidates had already been dealt with. However, new roads were still being made 40s where appropriate as late as 1990, the new single-carriageway St Mary's Way in Stockport, which has no houses along it, but runs through a zone of motor dealers and retail sheds, with numerous turnings, was given a 40 limit.

In the 1990s, the climate changed, in a way that is well-documented elsewhere on this site, particularly in Turning the Screw. Political opinion swung against the private car, and the simplistic "speed kills" mantra began to replace the balanced approach to road safety that had given Britain the safest roads in the world. Crucially, in the early part of the decade, the then Conservative government removed the requirement for local highway authorities to gain the approval of the Department of Transport before they made any changes to main road speed limits. This in effect gave them the freedom to do what they liked without any pretence of consistency or adherence to national guidelines, and all over the country we have seen a wave of inconsistent, politically motivated speed limit cuts.

It is not surprising that in this climate urban and suburban 40 mph limits were high on the list for attention, and reductions to 30 have occurred with depressing frequency all over the country. There are far too many to even give a representative selection here many can be found on my page of Speed Limit Reductions. Two examples of classic, lightly-developed, outer-suburban 40s being reduced to 30 are the A562 Widnes Road in Penketh, Warrington, and the A560 through Baguley in South Manchester. It is a quirk of road traffic law that vehicles may be parked at night without lights on a 30 mph road, but not on a 40 mph one, and this was actually advanced as a justification for a cut in the case of the dual-carriageway Mauldeth Road in Manchester.

It is not as if the removal of 40 mph limits has been done in any consistent manner. Highway authorities have not assessed their 40 mph roads to see which are most heavily built up, have most pedestrians and the shortest sightlines, but have simply responded in a piecemeal manner to perceived safety problems and complaints from local residents. Manchester, for example, has removed the 40 limits on the virtually undeveloped Victoria Avenue and Lightbowne Road, but retains them on considerably more built-up roads elsewhere in the city. Another borough within Greater Manchester retains half a mile of 40 limit on a road that even the keenest supporter of the concept might feel is a little marginal, while a few miles away within the same authority a two-mile stretch of undeveloped rural A-road has been reduced from NSL, half to 30, half to 40. I won't say where it is because it might give them ideas!

From the early 90s onwards, we also saw high-quality new urban roads being opened with 30 mph limits that ten or twenty years earlier would undoubtedly have been given 40s. One of the prime examples of this is the dual-carriageway A6010 Alan Turing Way running past the City of Manchester Stadium in East Manchester. Although it has at-grade junctions, this is a very good, well-aligned road with relatively little development along it, certainly much less than the A34 Kingsway, yet it has had a 30 limit from its opening. Another is the A677 Barbara Castle Way, part of the Blackburn Inner Ring Road.

Classic suburban 40 mph roads do remain, and one of the best places to see them is in Liverpool, where there are long lengths including the A562 Menlove Avenue, A5058 Queen's Drive, A57 Prescot Road and A580 Walton Hall Avenue. Manchester has the A5103 Princess Road and A34 Kingsway, the main routes into the city from the South, while in the West Midlands there are long stretches of 40 on the A38 Bristol Road running south from Birmingham city centre, and the A4123 Birmingham New Road, an archetypal inter-wars arterial road, is 40 pretty much all the way from the Hagley Road to Wolverhampton (although I suspect much of this was reduced from NSL as it became more built up rather than being increased from 30). But it would be a mistake to take these for granted, and given the current climate and some of the astonishing reductions that have taken place already, it would not entirely surprise me to see the notices go up to reduce Kingsway, for example, to a 30.

But, many will say, surely slower speeds are highly desirable in areas where there are houses and pedestrians. And isn't it the case that if a pedestrian is hit by a car at 40 mph, he only has a 10% chance of survival, whereas if he is hit at 30 mph, the chance of survival rises to 50%?

But this latter point ignores the fact that virtually no collisions between motor vehicles and pedestrians occur without some reduction of speed on the part of the driver. There is generally a significant difference between free travelling speed and impact speed. And a road that provides better visibility and sightlines for both drivers and pedestrians allows higher speeds to be attained without any degradation in safety. 40 limit roads are ones where there are likely to be fewer pedestrians, houses will be set back from the road and footways separated from it by grass verges.

Unless enforced by a battery of distracting speed cameras, merely imposing a lower speed limit on a road is unlikely in practice to result in significantly lower speeds if drivers perceive the new limit as being unreasonable therefore any supposed safety gain may be illusory.

The official guidelines for speed limit setting set out in DoT Circular Roads 1/93 say that the kind of environment for which a 40 mph limit is appropriate is:

"Partially built up (usually exceeding 50% of frontages). Buildings generally set back from road, sometimes with service roads. Undeveloped lengths between 30 and/or 40 mph limits and too short for a higher limit."
and that the character of the road should be:
Main traffic routes (e.g. ring and radial routes) with good width and layout. Adequate footways and crossing places where necessary. Parking and waiting restrictions.
i) By-passes and other important traffic routes which have become partially developed, or
ii) Main roads through some villages

It is unfortunate that this sound advice is now widely ignored by local highway authorities.

There is a clear difference in the road environment between a road with a properly-set 40 mph limit, and one where 30 is correct, and this should be reflected in a different speed limit.

By removing 40 mph limits where they are appropriate, a valuable distinction is lost, and ironically may make it more likely that drivers will ignore 30 limits on the large majority of urban roads where they are justified, as there will be no official differentation. Bad limits devalue good ones, and the end result may well be bad news for overall safety.

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