Have your say on our 20mph limits and zones in the Borough

The policy in full

Introduction

This 20 mph speed limit procedure supersedes the existing procedure from 2014. Its purpose is to provide the framework within which Rotherham Council will consider and assess the implementation of 20 mph speed limits.

The main theme of change in this new procedure is to set a clear rationale and assessment process in its application and include the opportunity for greater focus on the sense of place and community, including around schools. The new 20mph procedure will support active travel and will help minimising risk of death of serious injury for vulnerable users.

There are several 20 mph zones and speed limits already in place in Rotherham. The earliest 20mph zone to be introduced was that covering the East Dene and Herringthorpe area which was implemented in 1992. There are now 30 outside schools.

Background and policy context

Controlling vehicle speeds to 20mph or less is an important tool for improving road safety, particularly for vulnerable road users. Used carefully along with broader speed and traffic management tools, it is also an important tool for managing how traffic is distributed in the borough, enabling us to disincentivise use of less suitable routes as opposed to more suitable ones. Both of these are key considerations into the local and national approach to promoting walking and cycling. Furthermore, the Council receives requests for 20mph speed limits from residents, councillors, and community groups.

The vision of the Rotherham Transport Strategy[1] states that by 2026 Rotherham will:

Enjoy sustainable growth – new development will be based on compact mixed-use centres focussed on high-quality public transport.
Be a connected place – people and places are connected by an integrated, safe and efficient transport network.
Make sustainable travel choices – walking, cycling and public transport are a normal part of daily travel.

This strategy will be reviewed, commencing in 2023, as part of the production of the fourth South Yorkshire Local Transport Plan required by the Department for Transport – it is expected the emphasis on public transport and active travel will be strengthened as part of this review.

Both the South Yorkshire Mayoral Combined Authority Transport Strategy [2] and the Active Travel Implementation Plan [3] are supported by the provision of 20mph speed limits and 20mph zones. The considered use of 20mph limits forms a key part of Rotherham Cycling Strategy, with both the provision of 20mph limits and the retention of higher limits in appropriate places forms a key part of planning for cycling networks and infrastructure, working towards the principle approach of the strategy - that ‘’the highway network is the cycling network and therefore our approach should be to ensure the comfort, convenience, and safety of cyclists as standard”.

The Department for Transport (DfT) guidance relating to cycling infrastructure[4] recommends managing vehicle speeds to 20mph or less where cyclists are required to use the carriageway. DfT local speed limits guidance [5] provides the framework, key objectives, and practical application of speed limits for local (highway) authorities. The aim of the procedure is for Rotherham to respond to this guidance, and build upon it so as to add local speed limit management requirements.

The aim of this Council procedure is to ensure consistency in assessment and application throughout the Borough, for which a robust assessment process has been developed, and to unsure the deployment of 20mph limits is supportive of wider Objectives, including in the consideration of adverse or unintended impacts. A 20mph speed limit or zone must be appropriate for the part of the network it applies to, and must fit with its current or planned change in operation. Importantly, it must also be self-enforcing and operate without a reliance on police intervention – as discussed in section 3 below, the impact of tolerating high speeds within 20mph limits can be very significant compared against situations where drivers largely comply with the speed limit.

Impacts and limitations of signed only 20mph speed limits

Introducing a 20mph speed limit or zone to a road(s) where drivers are unlikely to substantially comply with the speed limit), will likely result in poor compliance, enforcement problems and understandable complaints. More significantly, failing to ensure 20mph limits are properly complied with substantially increases the risk to vulnerable road users relative to effective intervention, as can be seen in the table below. It is important to note that evidence is consistent that introduction of 20mph speed limits by signing alone typically only resulting in reductions in speed of circa 1-3 mph.[6][7] [8][9]. For this reason, we do not in general consider relying on signed only limits to achieve an acceptably low level of risk except where there is good evidence this will result in good compliance with the limit, typically in situations where only small (1-3 mph) reductions in speed area are required.

Effect of non-compliance with 20mph speed limit[10] e.g. for schemes using signs only

Change in incidence of casualties, relative to 20mph, where speeds are:

Speed	Comment	Killed	Seriously injured	Slightly injured
22mph	LTN 1/20 tolerance	+33%	+21%	+11%
24mph	ACPO FPN threshold	+73%	+44%	+22%
28mph	Typically effect of signed-only limit where before speeds are 30mph	+174%	+96%	+45%
30mph	For reference	+23%	+125%	+56%

The Council has a statutory duty to ensure the expeditious movement of traffic and efficient use of network through the reduction of delay and congestion. There is a need to encourage lower use of private car and other motorised travel in favour of walking, cycling and other sustainable modes. Whilst this is part of and supports the network management duty referred to above, care must be taken to avoid unintended network management consequences arising from lower speeds. In particular, there is also a need to encourage traffic to use more suitable routes in preference to less suitable ones, and speed limit procedure should support that need.

Benefits of 20mph speed limits

There is clear evidence of the effect of reducing traffic speeds on the reduction of collisions and casualties, as collision frequency is less at lower speeds, and where collisions do occur, there is a reduced risk of fatal and serious injury. The main improvement of reducing speeds below 20mph is to minimise risk of death or serious injury to road users, and especially vulnerable road users [11].

Research shows that on urban roads with low average traffic speeds any 1 mph reduction in average speed can reduce the collision frequency in urban areas by around 2 - 6% [12]. There is currently no evidence of migration of collisions and casualties to streets outside the zone. The research shows that for ‘casualty reduction the evidence is consistent in that casualties are reduced as a result of 20mph speed limits.’ Transport Research Laboratory (TRL) research regarding collision risk and speed, has shown that the benefit of reducing already low speeds is greater than reducing higher speeds [13] - this aligns with the network hierarchy approach proposed in this procedure, in implementing 20mph limits on minor roads where speeds are likely to be lower and so further reductions are likely to have most benefit, whilst permitting higher speeds on key transport routes where speed reduction is likely to bring less benefit, and where there are wider benefits in encouraging use of these routes as opposed to less suitable routes e.g. in residential areas.

Historically the majority of the 20 mph zones and speed limits that have been introduced in Rotherham were in response to an identified accident problem and include traffic calming to ensure drivers reduce their speed. Before and after accident studies carried out on these schemes show that accidents have been significantly reduced in these schemes, with some scheme recording no collisions in the ‘after’ monitoring period. National research has found that the reduction in accidents in 20mph speed limits supported with physical traffic calming to be around 40% - 60%, with greater reductions seen for child casualties (50-70% reduction) and casualties killed or seriously injured (50-90% reduction). Signed only limits are found to be much less effective, seeing collision reductions of around 10-20% [14].

Other impacts of 20mph speed limits

In addition to improvements in road safety 20 mph schemes also have other impacts. The extents to which this is achieved is dependent on the degree to which speeds are reduced, and there may be additional effects arising from any supporting traffic calming measures.

Active travel uptake
The evidence that 20mph limits in and of themselves increase active travel uptake is weak. Some studies have reported increased levels of walking and cycling as self-reported [15], but there is limited evidence by more objective observation. Some observations have reported little impact on observed levels of activity [16]. Studies abroad have failed to find any correlation between measured traffic speeds and cyclists’ perception of safety [17].

Emissions
Impacts of 20mph limits on emissions are mixed. Both steady-speed emissions curves, and more sophisticated models, suggest increased per-vehicle emissions [18]. However, in practice other factors (for example congestion, control delays, and driver behaviour in respect of acceleration and deceleration) may have greater impact, and increased per vehicle emissions are offset by reductions in traffic within the 20mph area (particularly where supported with traffic calming [19]). Where air quality impacts associated with 20mph schemes have been specifically investigated, impacts are reported to be negligible or slightly beneficial [20]. Emissions and energy consumption impacts (e.g. from electricity generation) may be different with electric vehicles [21].

Traffic levels & distribution
Broadly speaking, drivers can be expected to choose to take routes that are (or they experience to be) more expedient. Consequently, reducing speed limits can result in displacement of traffic out of streets in which the speed limit is lowered, onto those where it remains the same [22]. This can result in both advantageous and disadvantageous impacts, depending on particular circumstances.

Lower speeds may encourage drivers to use more suitable routes where these allow higher speeds [23]
However, reducing speeds on a road may incentive drivers to use other roads where speeds are already low (e.g. if more direct), which may result in increase traffic in unsuitable roads [24]
Traffic calming may result in particularly significant traffic reduction of around 20% on treated streets[25]

Road noise
Where speeds of 20mph are achieved, noise from road traffic may be reduced by as much as 5 decibels [26]. However this may be offset by impacts of traffic calming features where there are significant levels of commercial traffic (lorries and buses) [27]. Where possible schemes will be designed to minimise these effects.

Criteria

The criteria to be used for 20 mph speed limits and zones as follows. This should be applied to each road in an area under consideration, and not on the basis of averages across different roads.

Speed achieved after scheme is installed - 85th percentile speed should be less than 20mph.

85th percentile After speeds of up to 22mph can be accepted in low-risk situations i.e. where there is no record of collisions, where there is no route to school, and where there is no main cycle route).
The 85th percentile speed is the speed exceeded by no more than six in every seven cars in free-flow conditions.

"After” Volumes – Should not exceed 200 PCU/hr (ideal) 450 PCU/hr (general) 600 PCU/hr (exceptional).

PCU means passenger car unit, where a bus is equivalent to 2 cars, and medium and heavy goods vehicles are equivalent to 1.5 and 2.3 car respectively.

Bus usage - Preferably no buses, maximum 6 buses / hour each way on any street, except in a town centre location.

Schools

For roads passing by a school entrance used by pupils, a 20mph speed limits may be provided irrespective of traffic volume or bus criteria, over a length of 200m (minimum) to 300mm (maximum). This must be supported with traffic calming expected to achieve ‘after’ 85th percentile speeds of 20mph or less – where such measures are not feasible or deemed unacceptable (for example, owing to noise impacts associated with traffic calming on a route used by heavy goods vehicles), an advisory part time limit may be considered as an alternative. This is likely to be much less effective than a mandatory, self-enforcing limit, which should always be considered before an advisory limit.