Our approach is based on the Department for Transport’s (DfT) guidance which seeks a common national approach to setting speed limits.

Underlying principles

Before introducing or changing a local speed limit, we want to make sure that the expected benefits exceed the costs. Many of the costs and benefits do not have monetary values associated with them, the following factors are taken into account when considering speed limit requests:

  • collision and casualty savings
  • conditions and facilities for vulnerable road users
  • impacts on walking and cycling and other mode shift
  • congestion and journey time reliability
  • environmental, community and quality of life impact

Quality of life impact may include emissions, severance of local communities, visual impact, noise and vibration and costs, including of engineering and other physical measures including signing, maintenance and cost of enforcement.

Urban speed management

Summary of speed limit criteria in urban areas

The table shows a summary of the criteria for various urban speed limits.

Speed limit (mph)  Where speed limit should be considered
20 (including 20mph zone)

In streets that are primarily residential and in other town or city streets where pedestrian and cyclist movements are high, such as around schools, shops, markets, playgrounds and other areas, where motor vehicle movement is not the primary function.


In other built-up areas (where motor vehicle movement is deemed more important), with development on both sides of the road.


On higher quality suburban roads or those on the outskirts of urban areas where there is little development, with few cyclists, pedestrians or equestrians. On roads with good width and layout, parking and waiting restrictions in operation and buildings set back from the road. On roads that, where possible, cater for the needs of non-motorised users through segregation of road space and have adequate footways and crossing places.


On dual carriageway ring or radial routes or bypasses that have become partially built up, with little or no roadside development.

Street lit areas in towns - 30mph

Unless signed otherwise, street lit roads have a speed limit of 30mph. Signing is only required to indicate the beginning of a 30mph limit in a street lit area. Strict signing regulations do not allow repeater signs to be installed for 30mph limits by virtue of street lighting. The street lighting serves as the reminder of the speed limit.

For more information on urban speed limits, please see the DfT guidance. 

Rural speed management

Summary of speed limit criteria single carriageway roads with a predominant motor traffic flow function

The table shows the criteria for various rural speed limits.

Speed limit (mph) Where speed limit should be considered

Recommended for most high quality strategic A and B roads with few bends, junctions or accesses.


Should be considered for lower quality A and B roads that may have a relatively high number of bends, junctions or accesses. Can also be considered where mean speeds are below 50mph, so lower limit does not interfere with traffic flow.


 Should be considered where there are bends, junctions or accesses, substantial development, a strong environmental or landscape reason, or where there are considerable numbers of vulnerable road users

Villages - 30mph and 20mph

Fear of traffic can affect people’s quality of life in villages and it is self-evident that villages should have comparable speed limits to similar roads in urban areas. It is therefore government policy that a 30 mph speed limit should be the norm through villages.

It may also be appropriate to consider 20 mph limits or zones in built-up village streets which are primarily residential in nature, or where pedestrian and cyclist movements are high. Such limits should not, however, be considered on roads with a strategic function or where the movement of motor vehicles is the primary function.

More information on village and rural speed limits can be found in the DfT guidance

Requesting a speed limit reduction

For a speed limit reduction request to be formally considered by Dorset Highways, it should be submitted and fully supported by the relevant Dorset Councillor and / or town / parish council. For information on your Dorset Councillor or local town / parish council please see contact lists.

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