Introducing 20mph speed limits is proven to make a major reduction on road casualty rates (60-70%) . Furthermore, they take away the fear felt by families surrounded by fast moving traffic and encourage people to walk and cycle more! Schemes in towns such as Portsmouth and Kingston-upon-Hull have had good results and with this kind of evidence it's time for more councils, including Birmingham, to take action.
The speeds at which vehicles travel is directly linked to the severity of injuries sustained in the event of an accident. A pedestrian, if struck by a vehicle driving at 20mph, is likely to suffer slight injuries (2.5% dying). At 30mph they would be severely hurt (20% dying) and at 40mph or above are likely to be killed (90%). Reducing the speed limit to 20mph has a direct impact on pedestrian safety and is the principal reason for introducing a scheme. A Transport Research Laboratory study of 250 20mph schemes across Britain found that after the limit was reduced, crashes fell by 60%, child casualties by 67% and average speeds by 9mph.
Scope of Schemes
20mph schemes range in scope from a blanket city-wide approach to targeted zones in residential and/or commercial streets to schools only schemes. Schemes may be advisory or mandatory.
Current Schemes – Portsmouth
Portsmouth City Council was the first in Britain to make most of it's residential roads 20mph. Major routes remain unchanged. Its government funded plan has attracted national attention and stimulated interest from other councils.
The 20mph limit was proposed for roads where the average speed was already 24mph or less. They installed prominent 20mph signs where drivers enter the new speed restrictions, as well as 'repeater' signs as reminders. It has been found elsewhere that this method reduces speeds by 3-4mph. Road humps are not part of the scheme, although if speeds do not drop on particular roads, then residents will be consulted again to see if they want additional measures. In most cases the 20mph limit is self-enforced and further speed enforcement measures are not needed.
Kingston-upon-Hull – 20mph Champion
Kingston-upon-Hull now has over a hundred 20mph traffic calmed zones, covering over 30% of the city's roads, and they are pressing on to civilise more streets. Over 200 deaths or serious injuries and 1000 other injuries are estimated to have been prevented since the first zones were implemented in the 1990s. The total number of crashes within the 20 mph zones has fallen by 56%, the number of crashes with deaths or serious injuries has been cut by 90% and the number of child pedestrian casualties is down by 74%.
North Lanarkshire – 20mph Zones Using Signs Only
The results from a Scotland-wide trial of low-cost advisory 20mph schemes in residential areas were so good that North Lanarkshire Council decided to extend the three trial areas in its own area to all suitable residential streets. By March 2002 advisory 20mph speed limits covered the vast majority of residential roads in North Lanarkshire and there has been a significant reduction in casualties. The council is now piloting mandatory 20mph sign-only zones in three large residential areas.
Pros and Cons
The main pro is the issue of safety and, as described above, the severity of injuries is far less the lower the vehicle speed.
Additionally, groups such as "Living Streets" and "20's Plenty" argue that taking away fast traffic from residential and shopping areas results in an increase in cycle and on-foot journeys and make it less necessary to provide cycle paths.
Furthermore, there is an improvement in the quality of urban life when the emphasis shifts from the needs of drivers to those of the pedestrian. A classic study on the streets of San Francisco showed that traffic could have a profound effect on social relationships. It surveyed three streets almost identical in appearance, but differing markedly in their levels of traffic. The quietest street had a high proportion of families with children; people tended to know their neighbours and to have friends on both sides of the road. By contrast, the street with heavy traffic was inhabited mainly by elderly and single people who tended not to know their neighbours and who treated the street as hostile territory.
Detractors of 20mph limits argue that it will be too costly, too slow and that drivers’ attention will be diverted from the business of driving by attempting to keep their speed to 20 mph and negotiating the various traffic-calming measures.
Also, air quality is not likely to improve, nor is there any likelihood of any emissions benefit; the only way most modern cars can keep below 20 is by using low gears with higher revs, hence fuel consumption (and emissions) will not reduce.
Broadly, there is an argument that it is better to target, not blanket. The (road safety) point here is that the quality of residential and commercial roads are highly variable. The speed limit should reflect the conditions on the road, such as whether there are shops or houses, how broad, straight, well lit the road is or whether there are proper crossings and calming measures as you approach them. On some such roads, there is a case for 20, for some
30 is fine, while for others 40 is acceptable.
There have been a few school schemes such as the one in Oxford Rd in Moseley and parts of the city centre now have 20mph limits. Meanwhile groups such as "Pushbikes" and the "Cycle Network Project " promote lower limits as an incentive to cycling.
With ambitious schemes under consideration throughout the country from Aberdeen to London it's a good time for Birmingham City Council to raise the bar here in Brum.
Safer Routes to School Officer, Tim Hickey, has said that recently a new policy document has been drawn up regarding the introduction of 20mph near all Birmingham's schools. If it is approved this would be progress; but shouldn't we be looking to the example of the more ambitious councils like Kingston-upon-Hull or North Lanarkshire and taking it further?
BFoE is currently running a campaign to get 20mph on all roads in Birmingham that aren’t A or B routes, starting in Billesley. If you would like to get involved, please contact Ben Martin at email@example.com or come to our Transport Action Group meetings on 20th April and 18th May.