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Nearly all vehicles in 20mph zone that’s set to be scrapped broke the speed limit

01 Dec 2022 6 minute read
20mph sign. Picture by Carmarthenshire County Council. Inset Pictures: Caldicot Road leading to Portskewett and the junction of the B425, Caldicot bypass with Denny View (Google Streetview).

Twm Owen, Local Democracy Reporter

Almost all vehicles passing through a Welsh 20mph zone that is set to be scrapped did so above the 20 limit.  

Figures show that 99% of cars and other traffic travelling through parts of Caldicot, where the 20-mph limit will be lifted, were breaking the new maximum imposed as part of a Welsh Government trial.  

The former 30 mph limit is set to be reintroduced along part of the main B4245, known as the Caldicot bypass, and on Caldicot Road following a decision taken by Monmouthshire County Council which had put forward the town as a trial for the new, lower speed limit.  

No date has been set for when the 30 mph signs will go back up, but the council says it intends to do so as soon as possible.  

Following the trial, conducted at eight locations across Wales, the Senedd this summer passed a new law making 20 mph the ‘default limit’ for roads in built up areas in Wales from September next year.    

But Monmouthshire has said as a result of the Welsh Government clarifying rules around where exceptions to the new lower limit can be made it will reinstate the old, speedier limit at the two locations.  

Though the council has said it has acted in response to objections, which included claims traffic travelling at the lower speed was causing congestion, data shows the new lower limit was largely ignored.

The council has also said completition of the new 20mph zone could, that coincided with the start of a new school term, could have also contributed to reports of congestion.  

The same figures also show that a significant proportion of traffic was also travelling above 30mph at both locations, along the Caldicot bypass, near the junction with Denny View where speeds were recorded, and on Caldicot Road near the industrial estate.  

However, a council report says there was a reduction in overall speeds after the lower limit was introduced. The report said: “The data shows a significant and sustained reduction in mean, median and 85% percentile speeds at each of the monitoring locations”.  


On the B425, near Denny View, which is opposite Sudbrook Cricket Club, the percentage of vehicles exceeding 20mph was 99.6 in April this year, with implementation of the 20mph limit having begun from the end of March and completed on May 18.  

The percentage of vehicles travelling above 20mph remained at 99 per cent throughout May, June and July falling to a low of 99.2 per cent in May and creeping back up to 99.4 per cent in August. The council first stated its intention to restore the higher limit at the end of July.  

During the same period the percentage of vehicles travelling above 30mph was 85.6 in April which reduced to 59.6 in August and it reached a low of 46.6 in May.  

The mean speed, the average of all vehicles, reduced from 36.3 in April to 32.3 in August while the median, the speed most of the vehicles recorded had been travelling at, fell from 36.2 in April to 31.5 in August.  

The speed at and below that 85 per cent of vehicles were travelling at fell from 42.2 mph in April to 38.9 mph in August, a drop of 3.3 mph.  

The total number of vehicles passing the speed monitoring location fell from 217,948 in April to 175,541 in August, with the highest number being 223,580 in May.  

At Caldicot Road the percentage of vehicles travelling faster than 20 mph fell from 99.4 in April to 99.1 in May and June but creeped back up to 99.2 per cent in August.  

Those travelling faster than 30 mph fell from 91.4 per cent in April to 80.5 per cent in August with the figure having fallen to 77.5 per cent in July.  

The mean speed reduced from 39.3 in April to 36.6 in August while the median speed fell from 39 in April to 36.2 in August.  

The speed at and below that 85 per cent of vehicles were travelling fell from 46.2 mph in April to 43.8 mph in August, a drop of 2.4 mph.  

The total number of vehicles recorded increased from 110,666 in April to 142,642 in August with a peak of 149,585 in July.  

The council says: “a significant increase in traffic volumes between April 2022 and May 2022 in most locations is most likely due to the start of the school term, which combined with completion of the 20mph zone could account for reports of initial congestion while the scheme was new.”  

It also says the school Easter, summer and half term holidays and road closure for street parties during June’s Queen’s jubilee bank holiday, a month-long road closure at Church Road, Sandy Lane and Chepstow Road in April and May, and six-month Wales and West Utility gas works from June 20, with traffic lights on Newport Road, could all have affected the data.  


The legislation lets local highway authorities exempt some routes from the new 20-mph default limit if they meet criteria such as if there are few properties or community facilities along the roadside or where pedestrians and cyclists do not have to “mix” with vehicles.  

On A and B roads these exceptions cannot be applied within a 100m walk of any formal or informal entrance to a school, or 100m of a community centre or hospital, or where there are homes and shops facing the road and exceeding a defined density.  

Council officers agreed the criteria meant the very eastern end of the B4245, from Woodstock Way to the Castlegate roundabout, should therefore revert to a 30-mph limit. However, there will be a part-time 20 mph limit, on the section passing Durand Primary School, at start and end of the school day during term times.  

The change back to 30 mph on the section of Caldicot Road from the Castlegate roundabout to the bridge over the former railway line is being made as it passes through a business park without any residential properties fronting the road and the council says there is very little interaction between pedestrians and motorists.  

Public comments on the 20-mph limit also claimed motorists had difficulty overtaking cyclists travelling at 18 or 19 mph following the introduction of the lower limit. 


Welsh Conservatives have been strong critics of a ‘default’ 20mph limit.

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Richard 1
Richard 1
1 year ago

So it’s reported here that the new limit was generally ignored, but we have also seen claims that it caused congestion; can’t both be true can they?

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