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

85th percentile speed should be less than 20mph, must be less than 22mph

>20mph only acceptable where –

• Not a main cycle route
• Not on a route to school
• No record of NMU casualties

In advance of works

Before speeds, measured with reference to C185, adjusted to reflect measures proposed.

Adjustment should be on basis of tools to consider effect of measures (e.g. Speed Limit Appraisal Tool) and/or evidence of effectiveness of measures (e.g. information in LTN 1/07, TRL studies, etc).

Post completion

After speeds measured with reference to CA 195.

Both cases

Ensure likelihood of death or serious injury in event of collision is truly minimised.

Minimises enforcement burden.

Meet requirements of LTN 1/20.

Should not exceed in any hour

200 PCU per hour (ideal)

450 PCU per hour (general)

ATC data covering at least 2 neutral weekdays and a neutral Saturday.

Surveys need only be completed on streets expected to breach 200 vph threshold, based on Officer judgement, provided this is validated by surveys on other streets in the scheme being surveyed and being found to be broadly as traffic as expected or less.

1 pedal cycle = 0 PCU

1 motorcycle = 0.4 PCU

1 car = 1.0 PCU

1 LGV = 1.0 PCU

1 OGV1 = 1.5 PCU

1 OGV2 = 2.3 PCU

1 PSV = 2.0 PCU

To ensure network of distributor roads is legible and relatively attractive compared to access streets (i.e., encourage traffic out of minor streets)

To ensure 20mph limits are not utilised in attempt to avoid provisions for non-motorised users were requiring engineered separation and/or traffic reduction

To minimise non-credible limits where traffic volumes require geometries likely to invite speeds exceeding 20mph.

To minimise nuisance (e.g. noise) associated with traffic calming likely to mitigate said geometry.

Preferably no buses

Based on Rotherham bus map, counting in service buses only.

A town centre is defined as being: 

• Shown on the Rotherham Local Plan Key Diagram as being within a retail area
• Premises on both sides of the road are included in that retail area

To minimise non-credible limits where traffic volumes require geometries likely to invite speeds exceeding 20mph.

To minimise nuisance (e.g. noise) associated with traffic calming likely to mitigate said geometry.

To ensure fast, attractive operation of public transport.

Mean = less than 17

85th percentile = less than 20

A 20mph speed limit may have the unintended consequence of encouraging drivers to increase speeds given low ‘before’ speeds. Therefore repeater signing and markings should be avoided.

Centre line removal is recommended to support low speeds.

Mean = 18 - 20

85th percentile = 21 - 24

A signed only 20mph speed limit will likely be credible without additional intervention.

Centre line removal is recommended to support low speeds.

Additional measures may be appropriate at high risk locations (e.g. schools) to ensure speeds are kept below 20mph. Isolated humps, or humps at 90m spacings, can assist this.

Despite the likely small level of non-compliance, the incidence of fatal casualties can be expected to be 40% greater than for a credible limit (i.e. 85th percentile speeds below 20mph).

Mean = 21 - 22

85th percentile = 25 - 26 

A signed only 20 mph limit is unlikely to be credible in and of itself.

Centre line removal is recommended to support low speeds. Vehicle activated signs may be considered provided this does not lead to a proliferation of signing.

Physical traffic calming should be considered. Reduced carriageway width and horizontal deflection are options – it may be possible to adjust parking arrangements to achieve this effect. Humps at 140m spacings should achieve 85th percentile speeds averaged throughout the link, but peak speeds between humps may exceed 22 mph.

At high risk locations (e.g. schools) to ensure speeds are kept below 20mph. Isolated humps, or humps at 90 m spacings, can assist this.

Level of non-compliance in absence of additional intervention may appear minor, but the consequence of this can be expected to be as much as a near doubling (88% increase) in incidence of fatal casualties, relative to a credible limit – hence additional measures being required not withstanding DfT guidance.

Mean = 23 - 26

85th percentile =27 - 31

Physical traffic calming is required. Humps at spacings of no greater than 90 metres would be a typical response. At high risk locations hump spacing should be reduced to 60 metres.

The consequence of not intervening to ensure a credible limit can be expected as much as a trebling (218% increase) in incidence of fatal casualties, relative to a credible limit – hence additional measures being required not withstanding DfT guidance.

Mean = 27 - 33

85th percentile = 32 - 39

Physical traffic calming is required. Humps at spacings no greater than 60 metres are likely to be required.

Mean = more than 34

85th percentile = more than 39

Unlikely to be suitable for 20mph without major investment to fundamentally change the road’s use or environment.