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nope
- Modest Speed Reductions: A 2018 Department for Transport (DfT) review of signed-only 20mph limits found a reduction in median speed of less than 1mph.
The majority of residents, non-resident drivers and cyclists (between 69% and 89%) perceive 20mph limits to be beneficial for residents, cyclists and pedestrians
The study shows that 20mph limits are generally supported and there is little call for the limit to be changed back to 30mph;
There is an established positive relationship between vehicle speed and injury collisions – the higher the speed, the more collisions and where collisions do occur, the higher the risk of a fatal injury at higher speeds.
- Limited Impact on Casualties: A study of a 20mph intervention in Belfast city centre found "little effect" on long-term outcomes such as collisions, casualties, and speed, outside of reducing traffic volume.
A 20 mph speed limit intervention implemented at city centre scale had little impact on long-term outcomes including road traffic collisions, casualties and speed, except for a reduction in traffic volume. Policymakers considering implementing 20 mph speed limit interventions should consider the fidelity, context and scale of implementation.
Much larger effects have been demonstrated when 20 mph speed limit interventions are implemented city-wide in comparison to city centre. The example in Bristol has been used by many local authorities to support the introduction of 20 mph limits. Research evaluating the effectiveness of the city-wide 20 mph speed limit intervention in Bristol found statistically significant reductions in average traffic speeds of 2.7 mph, and a reduction in the number of fatal, serious and slight injuries from road traffic collisions, equating to estimated cost savings of over £15 million per year. Similarly, in a city-wide 20 mph speed limit intervention in Edinburgh, evidence highlighted that, following the implementation of the 20 mph policy, a further reduction in collision rates occurred. Specifically, the average number of collisions per month in Edinburgh in 1997 was 165, while in 2019 this number fell to 64.
- Low Compliance: Studies have noted that in some areas, compliance is poor, with up to 76% of drivers exceeding the 20mph limit in some zones, as reported in a 2024 analysis.
The most common area of concern across all user groups considered was around compliance, with most focus group and survey participants of the opinion that stronger enforcement measures are needed if 20mph limits are to be effective.
and of course with "every single" 20mph zone claiming 20-30% casualty reduction, we'd expect huge improvements in the fatality rate and total casualties. So where are they?

Do what?Mottie, and at least johnny2007 and aveatry, don't want you to do that.
Mottie, and at least johnny2007 and aveatry, don't want you to do that.I try to focus on the more serious issue as a rule of thumb.
Reduce pollution?!?!
I am no expert, but my experience is this: my former automatic gearbox won't engage third gear until car is over 23/24mph. So going at 20mph the engine is revving at 1300rpm. At 24mph it revs at 1000rpm.
Isn't the engine polluting more at 1300rpm?
Exactly.
At 20mph, almost everywhere here in west London, I see many drivers playing with their phones and even watch movies.
Too slow is not safer because the same drivers would be paying attention to the road if going at 30, so a pedestrian jumping on the road could be easily avoided.
Better not to be hit than be hit at 20mph.

If you had an electric vehicle then it wouldn't be a problem, would it?

Comrade Khan's
he refused to put out figures showing the so-called reduction in pollution in his expanded ULEZ zones before the mayoral election.

Some people are daft enough to believe them.

better to not be hit by someone who braked sooner, because they were more engaged in the process.

Changing a speed limit from 30 to 20 is optional, for the councils.
Lets not kid ourselves that councils don't make a healthy income from the motorist.

So would you support it being lowered to 10mph to reduce those numbers even further?

You do get that we have only had a 6% reduction in the number of people killed on roads in the last 10 years?
| Before 20 MPH limit | After 20 MPH limit | |
| Deaths on roads susceptible to 20 MPH limit | 100 | 60 |
| Deaths on roads not susceptible to 20 MPH limit | 567 | 567 |

Where I live there is no need for a 20mph limit because you would struggle to travel at much above 20mph on an 8' wide lane bordered by drystone walling & Hawthorn hedges.
Correct.It's starting to look as if the refuseniks, having tried cherry-picking data to "prove" that they're right to dismiss 20mph limits, and been caught out and thus failed dismally, are now starting to dismiss all data,