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Regular news: Issue 607 12 Oct 2012

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Road management / Maintenance, Road safety, England

Restore use of 85th percentile speeds for limit-setting, DfT told

The DfT is being urged to rethink its speed limit setting policy and give more emphasis to using 85th percentile speeds rather than mean speeds.

The call comes in responses to the DfT’s draft speed limit circular (LTT 20 Jul), consultation on which closed last week.

Derbyshire County Council has expressed concern about the DfT’s suggestion that signed-only area-based 20mph limits are appropriate if mean speeds on the streets are at or below 24mph.

Ian Stephenson, Derbyshire’s...

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Your Comments:

12 Oct 2012

I agree with Derbshire and ABD that the use of existing average speed as an indiactor of appropriate speed limits is misguided. I think our urban speed limits should be similar to those in France and Spain and we should use 5 mph increments between 25mph (40kph) and 40 mph to better reflect the changing characteristics of roads. 20 mph is too slow for widespread use.

17 Oct 2012

I agree that the 85th percentile speed would be a better system. Using the mean speed at 24mph or less is odd in that authorities would appear satisified that the "average" driver will be exceeding the posted limit. Using the normal distribution curve concept, this would equate to around 55% of drivers exceeding the speed limit, surely that level of non-compliance would be the subject of concern if it were the case in a 30, 40 or 50mph street with pedestrian and cycle movements expected.