Road Safety News

New study will probe whether twenty is plenty

Monday 12th June 2017

Image: © Copyright M J Richardson and licensed for reuse under this Creative Commons Licence

Researchers at the University of Edinburgh have today (12 June) launched a new study, which will evaluate the impact of 20mph speed limits in two British cities over the next three years.

The study, described by the researchers as the largest of its kind in the UK, will measure casualty and traffic accident rates in Edinburgh and Belfast to determine whether 20mph limits improve road safety.

Rates of cycling and walking will also be measured to assess the impact of 20mph limits on active travel choices, while local residents’ attitudes towards the lower limit – and how it has affected their quality of life – will also be assessed.

Researchers say the project, which is scheduled to run until 2020, could help inform authorities in other cities considering a reduction in speed limits.

The study is being  led by the University of Edinburgh and the Scottish Collaboration for Public Health Research and Policy, working in partnership with other UK universities, NHS Health Scotland and the charity Sustrans. Funded has been provided by the National Institute for Health Research.

Dr Ruth Jepson from the University of Edinburgh, said: "We are excited to launch this major project which we hope will provide very important insights into the public health effects of such initiatives.

Andy Cope, director of insight, research and monitoring at Sustrans, said: "We anticipate that our broad focus will generate a wealth of evidence and learning that will be invaluable for informing future roll-outs of similar schemes in the UK and around the world."

Another major study looking at whether 20mph limits reduce speeds and collisions, being carried out by Atkins on behalf of the DfT, has been ongoing since October 2014. While there is no firm date as yet for the publication of the findings, we understand this is likely to be late 2017/early 2018.

Want to know more about speed and road safety?
Online library of research and reports etc - visit the Road Safety Knowledge Centre
Key facts and summaries of research reports - visit the Road Safety Observatory (speed limits)


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Am I right in reading that this study will take 3 to 4 years before becoming published? What's the point then, 4 years to late to find out that it's a no brainer. Nice one whoever requested it.

Surely we should know whether it works or not and as regard to exhaust gasses as far as I am aware the general speed has only been reduced in many instances by only 1 or 2 mph and so I doubt that there will be any significant benefit shown.
Bob Craven Lancs

Agree (5) | Disagree (1)

Sorry for delayed response; I've been away. She got hit at 20 because she just stepped out without looking (talking to and looking at her friend!). The driver had no time to stop. Had the same occurred at faster speeds, I'm very aware that the consequences would have been far greater.
Jan James

Agree (1) | Disagree (6)

3 years on and it seems there is no measurable progress. To extract quotes from 20’s Plenty for Us Press Release Jan 2014 on the then YouGov survey on Bristol 20 speed limits:

73% of adults in GB agreed that ‘breaking speed limits is not acceptable in most circumstances’


71% of drivers agreed ‘people will ignore 20mph limits because they don’t see themselves getting caught by the police

20mph speed limits need engineering measures or routine (as in frequent) police enforcement to succeed. As for signed only 20s? - the elephant has still not left the room.
Pat, Wales

Agree (14) | Disagree (5)

Those doing the study might like to ask drivers using these roads whether they are actually aware of the prevailing speed limit anyway and if not, why not? If slower speeds do not actually result from lower posted limits, it's a fault of the drivers and not the limits. I suspect many drivers do not consciously check the limit (or much else) on the roads they're driving on - seeing no further than the vehicle in front of them and restricting their vision only to the width of carriageway between the kerbs - tunnel vision in other words. Their first inkling of danger is when the it appears immediately in front of them, when it is too late to react.
Hugh Jones, Cheshire

Agree (0) | Disagree (2)

Hugh. You have hit the nail on the head when you question that drivers should be able to see and stop in time in order to avoid a pedestrian. The 20 is plenty scheme focuses on only one aspect of road safety and that is speed. Believing or presuming that its only speed that is the danger and the killer when in fact no matter what the speed may be in principle if there is not safe space between vehicles then the problem will still exist. When drivers slow down in traffic there is a tendency to follow on like sheep and fixate on the rear end and lights of the vehicle in front. With such a short distance they lose peripheral vision being unable to see what's happening around them and they can also be hidden behind the vehicle in front vehicle. If it is a large one that will reduce considerably their forward vision and of spotting potential hazards. It also makes them invisible to other road users and that includes pedestrians who are more than likely to rush out believing that behind the next vehicle there is a safe space. Kids and other older pedestrians are well known for taking chances when crossing the roads and will take chances where common sense should dictate otherwise.

So more vehicles will effectively be tailgating. Further with such a lower speed the drivers concept of danger is not the same and his concentration is more likely to taken in other ways and as a result his safety and the safety of others is undermined and its more than likely that more incidents will occur as a result.

The 20 mph scheme also fails to take into account the most numeric and prolific causation of accidents involving vehicles. We have identified tailgating and being rear ended particularly at junctions and roundabouts, the next is at T junction and 'smidsys' where speed in general is not a relative factor but perhaps could be made worse by slowing drivers down. Some drivers feel under pressure therefore they feel that they have to make progress and are frustrated by the lower speed limit. So with vehicles being driven slower and giving less safe space the opportunities to move out at junctions will be further reduced and a greater danger is manufactured.

Its been running in some areas for over 10 years now and no one has come to an absolute conclusion that it works.
Bob Craven Lancs

Agree (10) | Disagree (4)

The research is welcome as we believe that all data is good data. But its value comes from putting it into the appropriate context. It should be looking at the wide benefits in terms of active travel, public health, livability, community cohesion, emissions as well as direct road casualties.

In looking at just two implementations, the small city-centre scheme in Belfast and the wide, partially implemented Edinburgh scheme, it will be able to provide a depth of analysis as well as breadth.

It will complement other research and pilots by local authorities that shows that communities value their wide-area 20mph limits and such organisations as WHO who say that 30kmh/20mph is the standard for where drivers of motor vehicles wish to mix with pedestrians and cyclists.

Of course the other side of this research is that it will, by implication, be assessing whether blanket 30mph limits on residential roads are still fit for purpose. We, like many other organisations, believe that they belong in the 20th century.
Rod King, Warrington, Cheshire, 20's Plenty for Us

Agree (6) | Disagree (17)

Jan: Was your daughter actually hit at 20mph, or had the impact speed reduced from this? I'm sure we're all glad she's okay obviously, but the thinking behind the 20 limit is that drivers should - if driving at or below this limit - have time to see and be able to stop short of actually colliding with, a pedestrian.
Hugh Jones, Cheshire

Agree (6) | Disagree (1)

I,for one, was grateful for the 20mph speed limit when my 14 year old daughter got knocked down. A few bruises and knocked confidence but otherwise okay. I don't want to even consider the alternative with faster moving traffic.
Jan James - Good Egg Safety

Agree (2) | Disagree (6)

I'm beginning to wonder whether or not 20mph zones & limits are a ruse to help plug the shortfall in road infrastructure budgets.

You'd expect roads in long standing 20mph zones and limits to be in a relatively decent condition (light wear), yet, in my local area at least, they are in a dire condition.

To the point where it's not speed cushions or chicanes that provide speed management functions, but avoiding potholes and those dilapidated speed cushions that double as tyre spikes.
David Weston

Agree (16) | Disagree (1)

Perhaps it would be useful to investigate the other possible attitude and that is of local businesses, drivers or firm managers, taxis, buses etc. to find out what they think of the reduced speed limits and if its had any effect detrimental or for the better upon their businesses.

It seems to transpire from other reports that the mean speeds have come down by on average just over 1 mph. Obviously other traffic calming measures may have to be considered in order to encourage traffic to slow even further and to make drivers obey the new speed limits. It's about time we saw some justifications for all the time and public monies spent on this intervention as some areas have had 20 mph schemes for over a decade so we should now be able to justify its effectiveness and costings in terms of road safety of course...... or not. By the way can I ask who is funding this research? Is it from an independent source or from one with a possible interest in the results. I think it should be completely independent.
Bob Craven Lancs

Agree (13) | Disagree (2)

Hopefully they'll think to measure the change in speeds (if any) at the outset! If there's little reduction in actual speeds on the roads being studied, an assessment of the effectiveness of posted limits by just measuring collisions on urban roads, will be inconclusive.
Hugh Jones, Cheshire

Agree (10) | Disagree (0)