Between 2011 and 2015 Bath and North East Somerset Council (when it was Lib Dem-led) spent £871,000 bringing in 13 new zones with a 20 mph speed limit. The Daily Telegraph reports that they have caused an increase in accidents. The rate of people killed or seriously injured has gone up in seven out of the 13 areas. The reductions had been seen in central Bath whilst the worsening is largely in outlying rural areas.

The Council’s assessment says:

“Nationally, this adverse trend is also prevalent in other authority areas. In one notable case in Portsmouth, one of the earliest area based projects, it was reported that “the number of people killed or seriously injured actually went up, not down, after the limit was lowered”. There is no simple explanation for this adverse trend but it could be that local people perceive the area to be safer due to the presence of the 20mph restrictions and thus are less diligent when walking and crossing roads, cycling or otherwise travelling.”

Another explanation could be that drivers are looking at their speed dial rather than the road.

Some would argue that the problem was that these schemes only had signs, that if they had put humps everywhere it would have had more impact. Certainly the reduction in speed (an average of 1.3mph) was modest. There is also the increase in pollution from humps – which also costs lives. Then there is the damage humps cause to the emergency services: the London Ambulance Service estimates they cause well over 500 deaths a year in London. There is also a lack of conclusive evidence that humps reduce the number of accidents. In Barnet the number of accidents fell after humps were removed.

Cllr Patrick Anketell-Jones, the Conservative deputy leader of the Council, thinks “the report is essentially right” but that the Council can’t afford to scrap the zones. He says:

“It has cost over £800,000 to roll out the 20mph zone and it would probably cost the same to reverse them.

“We just haven’t got the money. I’m pretty sure the 20mph zones will stay in place for the foreseeable future.”

Would it really cost as much to remove the signs as to make them and install them? I think Cllr Anketell-Jones should press his council officers on the point. Could they not at least get rid of the signs in the areas where they have done the most damage?

Certainly it is appalling that such a large sum has been spent on the pretext that it would improve safety when its impact would seem overall to have been detrimental. If councils wish to spend money to reduce the number of accidents should they not do so in ways where the evidence is solid that it will produce the desired result?

Those councils who have adopted such schemes should check if they are working. Preferably this should mean bringing in some reputable independent outfit – not just allowing the Council’s highways department to mark their own homework with an internal study.

Earlier this year an analysis commissioned by Manchester City Council on their 20mph zones concluded:

“Overall the results show that casualties in the phase 1 20mph area have not reduced as much as the casualty numbers citywide.”

In Merton the evidence of the impact of 20mph zones was inconclusive. The failure in Portsmouth referred to earlier is detailed here.

The Institute of Advanced Motorists, a road safety charity, produced what strikes me as a shocking indictment of 20mph zones in 2014. It found the number of serious accidents on 20mph roads has increased by over a quarter on the previous year, according to an analysis of government data. Slight accidents on 20mph roads increased by 17 per cent.

In the same year, there was a decrease in the number of serious and slight accidents on 30mph roads and 40 mph roads.  Serious accidents went down nine per cent on 30mph roads and seven per cent on 40 mph roads. There was a five per cent reduction in slight accidents on 30 mph roads and a three per cent decrease on 40 mph roads.

Casualties in 20mph zones also saw a rise. Serious casualties increased by 29 per cent while slight casualties went up by 19 per cent.

The Institute’s chief executive, Simon Best, said:

“The government and councils need to take stock on the effectiveness of 20mph signs.  Recent advice, guidance and relaxation of regulations has all been about making it easier for councils to put 20mph limits in place.

“More and more roads are being given a 20mph limit but they do not seem to be delivering fewer casualties.  The IAM are concerned that this is because simply putting a sign on a road that still looks like a 30mph zone does not change driver behaviour.  More evaluation and research is needed into the real world performance of 20mph limits to ensure limited funds are being well spent.  In locations with a proven accident problem, authorities need to spend more on changing the character of our roads so that 20mph is obvious, self-enforcing and above all contributes to fewer injuries.  In Europe, it is long term investment in high quality segregated or shared surfaces that have led to a much safer environment for cyclists and pedestrians.”

So there are also questions for the Department of Transport. It provides huge sums to local authorities to spend on schemes that are supposed to be saving lives but may well be doing the opposite. An assessment of the effectiveness of 20mph zones was due to be published by the department this year and is now expected in another six months. I hope it will be a robust and thorough report. It may be politically embarrassing if the whole effort has been a complete disaster. But the sooner the truth is faced the better. At the very least the Government should prevent any further 20mph zones being funded until the Department’s review is produced.