Archived on 6/5/2022

New report on effectiveness of 20mph limits

anon3821395

24 Nov '18

The report:

In residential case study areas, the introduction of 20mph limits is estimated to have resulted in a 0.8mph reduction in median speeds and a 1.1mph reduction in 85th percentile speeds on ‘important local roads’.

In city centre case study areas, the analysis shows a 0.6mph reduction in median speeds and a 1.0mph reduction in 85th percentile speeds.

This study has found no significant safety outcome (in terms of collisions and casualties) in residential areas, based on the post implementation data available to date. Due to the small sample sizes and variability in the data, the statistical analysis undertaken to date indicates that the real change could be positive or negative. In addition, it has not been possible to draw any conclusions regarding the relative change in fatal injuries, cycle casualties, and casualties involving older people.

In light of this report, how do you feel about Lewisham’s blanket 20mph limit?

jayB

24 Nov '18

I find it staggering that Lewisham have wasted money on rolling this out without a pilot and without any evidence to back it up.The buses crawl even more slowly than they used to especially the 176. Even without evidence re the effectiveness of 20mph limits, logic would dictate that if people are speeding may be they don’t speed in accordance with any speed limits but drive as fast as they like! Another example of ideology over effectiveness.

anon3821395

18 Jan '19

A recent Council Meeting has revealed some stats on the effectiveness of the blanket 20mph limit.

Notably:

2.4
The report seeks approval in principle to include the possible use of average
speed cameras for enforcing the speed limit where the use of physical
measures such as speed humps, speed cushions, chicanes etc. is impractical,
prohibitively expensive or would result in unacceptable dis-benefits to other
road users such as emergency service vehicles and buses etc. This is only
likely to occur on the larger Lewisham roads such as Downham Way, Brockley
Road, Southend Lane etc. Note that if this technology is found to be feasible a
further report will be presented to Mayor and Cabinet with detailed proposals
seeking agreement to their use.

…

5.5
February 2018- Post implementation report finalised giving information
of the effectiveness of the signed only scheme. Note: - this report was
mainly concerned with speed changes (reductions) and not collisions as
only four months post 20mph limit introduction collision data was
available which was insufficient for comparison purposes.

5.6
The overall speed reduction achieved over all sites surveyed was 0.5mph

The budget for 2018-2020 is roughly £1,168,988.

A 0.5 mph reduction has been achieved so far. No evidence forthcoming of improvements in safety.

Let’s see what happens next…