WHEN considering a 20mph speed scheme, councils must consider guidance from the Department for Transport.
There are two types of initiative: limits and zones.
A limit includes the use of speed and repeater signs alone but crucially, a zone approach requires suitable traffic calming measures, such as speed bumps, which results in average speeds lowering enough to not need active enforcement.
A DFT report considering the effect of a 20mph initiative in Portsmouth concluded speed limits reduced average speeds by less than zones, partly because limits are most effective where speeds are already low.
Zones should generally be implemented where traffic calming measures are required to bring down higher average speeds.
In Worthing, residents are being consulted on a limit scheme, with no plans to introduce further traffic calming measures.
But the current proposal includes many streets in which average speeds may be too high for a limit scheme alone to significantly reduce speeds.
A report to the CLC suggests around 17 streets may require traffic calming, at a cost of up to £1.2 million. The costs are not included in the budget set-aside for any potential 20mph initiative.
Is there any point in having 20mph limits?
AVERAGE speeds on nearly half of roads surveyed may be too high for a 20mph speed limit to be effective on its own.
The DFT states that introducing limits on roads with average speeds of 24mph or less is most likely to lead to a ‘general compliance’ with the new 20mph limit, as speeds are already low.
Of 142 roads surveyed in Worthing, 43 per cent had an average speed of over 24mph, while the rest conformed with the guidance.
‘20’s pointless’ argue the current drawings for the town’s limit scheme includes far too many of these ‘unsuitable’ roads and should be excluded from the proposals.
Elise Mason said: “The proposals being consulted on include far too many roads in which speeds are too high to bring speeds down to 20mph by using signs alone.
“We believe the scheme is doomed to fail without expensive and unnecessary traffic calming measures, for which there is no budget.
“Also to put in 20mph signs where speeds are already around 20mph is completely pointless.”
Government research suggests implementing a 20mph limit reduces average speeds by up to 2mph.
This is a key factor in determining the recommended 24mph cap.
So what is the point of introducing 20mph limits on roads where people are already driving at 20mph?
Duncan Kay said: “If average speeds are around 20mph most drivers obviously feel this is an appropriate speed, in fact some are driving slower.
“The problem is that others are driving faster, some much faster.
“Introducing a 20mph limit sends a clear message that the appropriate speed for minor residential roads is 20mph or lower.”
In response to criticism of the planned inclusion of some roads, West Sussex County Council principal engineer Richard Wells said: “There are some unsuitable roads on there but the criteria we were given was to create a borough-wide scheme.
“We could out take a road where speeds are above 24mph but potentially, you could throw out a whole neighbourhood. The scheme is liable to change, depending on the results of the consultation.”