A decision made at speed: 20mph zones revisited


By - Friday 5th January, 2018

Croydon Council has brought in 20mph zones – what impact will they have?


Photo public domain.

The 20-mile-per-hour zone argument has surfaced again, with news from a council in the south west of England that since their introduction, accident rates have gone up. Closer to home, here in Croydon, signs have appeared at the end of my street following the introduction by Croydon Council.

Unlike when I started writing for the Citizen, I am now a candidate for the Conservative Party at this year’s council elections. However, I do not see this as a political issue per se. The council in the south west was led by the Conservatives; the 20mph zones were introduced here in Croydon by Labour. I do see this as an issue where decision makers need to consider different points of view and make a judgement based on weighing the arguments for and against. Not for the first time here in Croydon, I was disappointed that this did not happen.

There was no measured discussion. We saw little more than a selective quoting of statistics by people who had long ago made up their minds based on dogma. Our Labour council had decided that they wanted to do it, and that was that. With a nod to local democracy, they promised a local vote on the issue – but when it looked like they might lose, they opted to shortcut the process.

Let’s concentrate on road safety – not pollution

As succinctly as I can, here is my synopsis of the road-safety argument. There are other arguments related to the impact on pollution – but data is very limited, and I would be prepared to argue the case either way, so let’s concentrate on road safety.

There is no doubt that 20mph zones can significantly reduce accidents and injuries. The best source I have found was published in the British Medical Journal (BMJ) in 2009. The study was even based on data from London. Aha! You may say. Case proved!

Not so fast. These ‘zones’ included road-engineering interventions such as speed bumps, and were likely to have been selected for their suitability. To be precise, and we need to be precise, the study shows 20mph zones in the right place and with the right supporting measures can reduce accidents and injuries.

A 20mph ‘zone’ includes traffic-calming measures

The Royal Society for the Prevention of Accidents (RoSPA) has also looked at the issue. Its guidance issued earlier this year uses the same nomenclature as the BMJ study – a 20mph ‘zone’ includes traffic-calming and other measures, a 20mph ‘limit’ consists only of limit signs.

RoSPA encourages the wider use of limits – but wider use where? The Department of Transport’s view is that 20mph limits are appropriate for roads where average speeds are already low (below 24 mph), and the layout and use of the road must give the clear impression that a 20mph speed or below is the most appropriate. Where in Croydon’s road network is suitable?

What sections of road have average speeds of 24mph or less? No data appears to have been gathered, so that’s a ‘don’t know’. Would it not have been sensible to gather some representative data before making a decision? You might well think so.

Is putting up 20mph boards on short streets a good decision?

In some streets, such as my own, less than 100 yards long and ending in a dead end, I think we can guarantee that speeds are much less than 24mph. There will be other similar streets in the borough.

Can we be confident that putting up 20mph limit boards here is a good decision? Not necessarily, because money is only wisely spent when it makes a difference. In a street such as mine, where I doubt anyone has ever gone more than 20mph, and the adjoining street is a 30mph trunk road, it is money spent to no effect; money that could better be spent somewhere else.

Which leads to the final question. Even if all the criteria recommended for implementing a 20mph limit are met, we should also ask whether there is a better alternative? Is perhaps the main issue poor visibility, such that cutting hedges or imposing parking restrictions would be more effective at reducing accidents?

Most of these key questions were never asked by Croydon Council

Once we have answered all these questions, it might well be that 20mph limits are the answer for some, maybe even the majority, of Croydon’s quiet residential roads. My gripe with Croydon Council is that most of these questions were never asked, that when they were raised by others they were ignored, and that the consultation on the issue was a sham.

However the suggestion that Bath and North East Somerset Council should jump to reversing their scheme based on the evidence they now have is equally faulty. Once the money has been spent, spending more money to get back to where we were is a different question. I can envisage a situation where it might be sensible – but I would take a lot of convincing for my street. Taking down the 20mph boards would be as pointless as putting them up in the first place.

Robert Ward

Robert Ward

Engineer and project manager specialised in helping businesses make better strategic decisions and improve safety, quality and effectiveness. Conservative Party Councillor representing Selsdon and Addington Village on Croydon Council. He tweets as @moguloilman.

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  • http://www.20splentyforus.org.uk Rod King

    For an analysis of the Bath and North East Somerset report and comment on the various bogus news articles about the report, see http://www.20splenty.org/freddie_star