One of the pillars of the New Mobility Agenda approach to sustainable transport in cities, is to slow down the traffic. It works as an environmental trigger. Thus when you start to go slower, when you organize your daily life around this principle, you necessarily end up going less far. Which in turn sends out a whole range of signals for land use in our cities. The exact opposite of the forces behind urban sprawl and all that goes with it. If there were one first step to take, slowing things down would have a strong claim to this place of honor. And this movement is gaining real force in Britain.
Portsmouth – Britain’s First Twenty is Plenty (mph) City
Portsmouth has many claims to fame, home of the British Navy, Western Europe’s most densely populated city and now the first city in Britain to set a 20 mph limit across its residential road network.
What sets the 20 mph speed limit in Portsmouth apart from the other two and a half thousand 20 mph zones in England is not just that it is city wide, but also that it relies not on traffic calming or speed cameras for enforcement, but simply signs and publicity to encourage driver behaviour change.
It could be argued that this is one of the largest travel behaviour change initiatives in the country, and although the main objective for the scheme is safety, there are potential modal shift benefits which the city hopes to realise.
How the scheme works
The scheme was made possible by the amendment to Section 84 of Road Traffic Regulation Act in 1999 which allowed local authorities to set local speed limits without the need to get Secretary of State approval.
Due to a high population density, Portsmouth streets were largely already slow moving, so while the decision to go for a city wide 20mph limit was brave; it was not without local support.
The 20mph limit was launched in six city sectors, with the first introduced on 1st October 2007 and the last in March 2008.
In line with DfT guidance the streets included in the scheme were largely residential where average speeds were already below 24 mph, and while the strategic roads network was excluded, they have included some high volume routes where average speeds were above 30 mph.
Following a media campaign and wide scale community consultation process, streets that were to be included within the 20 mph limit had roundels painted at the entrance together with 20 mph signs, with repeater signs placed at 150m intervals along the length of the route.
The speed limit has been largely self-enforcing, with local residents being proactive in reporting speeding traffic. Traffic speed surveys have been used to identify problem streets, which have then been reported to the partnership of police and council officers, which swoop on offending drivers several times a year. The support of local motorists to the 20 mph limit is essential, so rather than just issue a penalty notice, police offer offending drivers an option of attending a half hour seminar educating them on the danger of speeding, which has proven very effective.
How Behaviour Change Interventions have been used
For a project of this nature, where the aim was a culture change, promotion and consultation has been the key.
To highlight the benefits of lower speeds the city first targeted the most vulnerable road users, school children, and issued each school child with pamphlets listing the roads which were to have a slower speed limit. The pamphlet included a ‘Frequently Asked Questions’ section and a hotline was set up for further information.
Posters and informational leaflets were distributed at public places such as schools, community centers, health centers, libraries, churches, sports clubs and universities.
Neighborhood forums were extensively consulted, with city officials going out to talk to them about the proposals and to listen to their concerns.
The local media and press, while initially skeptical, soon understood the potential benefits, and published many positive articles about the scheme. While the city also published statutory notices in local newspapers.
While of course there were some very vociferous objections from a small minority, overall objections were in fact minimal, and the vast majority of messages received by the city were in support of the proposals.
How effective has it been?
Since the scheme is so new, it has been difficult to gather clear robust evidence of effectiveness, but initial results appear positive.
Speed surveys show that there has been a reduction of about 0.9mph in the residential roads where average speeds were previously at or below 24 mph.
The most effective measures were actually on streets where speeds were previously above 30 mph, which have seen average speeds fall by as much as 7 mph.
While very few physical calming measures have been used, extra space has been provided for pedestrians and cyclists, and straight roads have been made to meander in those streets which had recent fatalities.
Initial evidence show a reduction in traffic incidents, and overall casualties are down across the city since the implementation of the 20 mph limit.
The potential for modal shift
There is anecdotal evidence that some modal shift has already been achieved, but so far there has been no study to confirm if this is the case. However since road danger is usually cited as the primary barrier to cycling, it seems logical to assume that a city wide reduction in speeds would have some impact.
Promotion of the 20mph limit initially targeted schools as an extension of the safe routes to school programme, and children have been encouraged to celebrate the introduction of the lower speed limits. This link between school travel plans and the safe speeds initiative should reinforce each other and help increase sustainable travel to school in the future.
It is known from other initiatives that when packages of measures are applied together such as parking controls, PTP, WTP, bus priority, then this does have a significant impact on modal shift.
While this has not yet been applied in Portsmouth, the smarter choices team have been included from the beginning and future modal shift promotion is planned, with ideas such as community street parties being considered.
While the overall speed reduction and impacts on accidents is much greater for a traffic calmed 20mph zone, than a city wide 20mph limit without accompanying calming, there are distinct advantages of a city wide limit.
The costs are much lower, and issues over emergency vehicle access, noise generation are avoided. With lower costs and less resistance to the initiative from the media and public, it has been possible to roll out the limit city wide in a very short space of time. This is a huge benefit in itself, since residents of the city all gain from living in a 20mph street themselves; they are also much more likely to respect the speed limit for neighboring communities that they drive through.
While it has so far not been possible to evaluate the full benefits of the limit, initial evidence seems to show that road safety has improved, and with a coordinated smarter choices follow up initiative it seems certain that significant modal shift benefits could be gained from the scheme.
Thus the ultimate benefits could be many; public health, well being, noise, pollution, climate change, reduction in accidents, deaths, reducing NHS and police costs.
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About the author:
Rory McMullan works for PTRC Education and Research Services, which organises training events for transport professionals on topics such as Portsmouth’s introduction of a 20 mph speed limit. As a cyclist and father, Rory is a strong supporter of slower speed limits in cities, because road danger caused by fast moving traffic is one of the main barriers to the take up of cycling, and the biggest concern for protecting the safety of children, whether walking, cycling or playing on our streets.
* Speed limit to be cut to 20 mph in government bid to reduce number of road deaths – http://www.dailymail.co.uk/news/article-1171706/Speed-limit-cut-20mph-government-bid-reduce-number-road-deaths.html
* 20mph speed limit on residential roads in Portsmouth – http://www.portsmouth.gov.uk/living/8403.html
* Related World Streets articles: http://newmobilityagenda.blogspot.com/search/label/slower