The Sun, 20 mph speed limits, and a lot of nonsense

CONTROVERSIAL 20mph speed limits designed to cut road casualties are not working, official figures show.

So says The Sun anyway*. So, what’s the problem?

A report from the Department for Transport shows there were 2,262 fatalities and injuries in 2011 on 20mph roads in built-up areas — 24 per cent more than in 2010 when 1,827 were recorded.

That compares to a one per cent reduction in casualties on 30mph roads in built-up areas.

How many people died or were injured on roads with a 30 mph speed limit then? The Sun doesn’t say, but the official data is easy enough to find. In 2010, 127,377 people were killed or injured on a road with a 30 mph speed limit. In 2011, it was 125,494.

In other words, that “1% drop” corresponds to almost 2000 fewer people were injured on 30 mph roads, while 400 more people were injured on 20 mph roads. That is a net decrease of 1448 injuries/deaths.

Just looking at the number of injuries on 20 mph roads is not going to tell you about how effective 20 mph speed limits are. You have to compare them with other speed limits. Data about how many 20 mph zones there are is hard to find, which makes making sense of the Sun‘s data difficult, but it certainly looks like a lot of them have been springing up lately, so an increase in injuries is to be expected – if there are more roads, there will always be more accidents!

Studies of 20 mph zones consistently find that the same stretch of road will see fewer accidents and fewer injuries if the speed limit decreases from 30 mph to 20 mph, especially if this decrease is enforced by speed bumps and other traffic calming measures.

* Incidentally, far from being “controversial”, surveys consistently find around 74% in favour of 20 mph speed limits and just 12% against them.

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  1. #1 by Joe on Saturday, 11th August 2012 - 11:12 UTC

    Another statistic missing from the Sun’s “report” is the speed of the vehicles involved in the incidents on 20mph roads. My own experience suggests that (unenforced) a 20mph limit succeeds in reducing the speed of most cars passing through it to around 30mph.
    This would perhaps be covered in the “false sense of security” that is mentioned – pedestrians are expecting cars to be travelling at or below the speed limit, when in fact they are travelling 50% above it.

  2. #2 by BrownhillsBob on Saturday, 11th August 2012 - 15:47 UTC

    killed or injured. 127k+ people were not killed. Critiscising stats? Sort your classifiers.

    And I’m on your side…

    • #3 by atomicspin on Saturday, 11th August 2012 - 23:19 UTC

      Whoops, typing error. Thanks, fixed.

  3. #4 by Stephen Humphreys on Saturday, 11th August 2012 - 22:18 UTC

    At least it wasn’t 20 kph! you’d be better off jogging. Long live MILES!! :-)

  4. #5 by Robin Smith on Tuesday, 14th August 2012 - 11:57 UTC

    Wouldn’t it be great if all users of the highways could step back for a moment and say:

    “How about we ALL forget about the rules and ourselves, and start paying a little more respect to ALL other road users?”

    Wouldn’t that be a great thing?

    Wiggins could have said something similar when he recently called for a ban on cyclists using ipods and compulsory helmet laws:

    “How about we all of us, INCLUDING CYCLISTS, paid a little more respect to other users of the highways”

    Traffic lights, speed humps, 20MPH etc are very much like rent controls. They only move the problem to a deeper level and distort the system. Whereas we need to face up to the root cause.

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