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Speed limits and road signs

How we set speed limits and use vehicle activated road signs.

Speed limits

Speed limits can be an emotive subject. Excessive speed is one of the main causes of road casualties in Britain. People want lower speed limits where they live, yet many still drive too fast generally.

We are committed to reducing the number of people killed and injured in road accidents and improving conditions for all road users, including vulnerable groups such as pedestrians and cyclists. Appropriate speed limits can help us achieve this.

The Department for Transport (DfT) sets limits on motorways and trunk roads, and also sets the 'default' limits which apply to all roads - these are 70mph on dual carriageways, 60mph on single carriageways and 30mph where street lighting is provided. It also issues general advice on setting speed limits on other roads.

We are responsible for setting the limits on all other roads in the county.

How speed limits are introduced

A Traffic Regulation Order is needed to set a limit that differs from the 'default', including 30mph limits where there is no street lighting. They are also needed to set a limit higher than 30mph where there is street lighting. We have to consult extensively when making a Traffic Regulation Order to check that the proposed limit has overall support from the community.

Once approved, signs have to be provided to show the start and end of the limit and also in most cases 'repeater' signs are required within the limit.


A major review of speed limits in villages was carried out between 1999 and 2003 which led to a large number of new limits to address community concerns over speeds.

In 2006 the Department for Transport issued revised guidance on the setting of speed limits and asked local authorities to carry out a comprehensive review of the limits on their A and B roads to take account of this guidance, which was completed in Oxfordshire in 2011, meeting the timescales set by the Department for Transport.

We review other requests for changed limits from members of the public and parish and town councils, although unless there are safety problems or changed circumstances (for example new development) it is difficult to fund these given other pressures on our budgets.

Appropriate speed limits

  • 20mph limits and zones may be appropriate in residential areas or streets with high numbers of pedestrians or cyclists (for example in town centres,  suburban shopping areas, and by schools). Department for Transport guidance on setting speed limits recommends that such limits should be self-enforcing, and so a 20mph limit will typically only be judged to be appropriate where existing average speeds are at or below 24mph, or  -where speeds are currently above this level - traffic calming or other speed management measures are provided in conjunction with the introduction of a 20mph limit.
  • 30mph limits are the norm for towns and villages
  • 40mph limits are typically used in less built up areas (for example at the edge of larger villages and towns)
  • 50mph limits are mainly used on more rural roads with a poor accident rate

The legal ‘Traffic Regulation Orders’ for known Oxfordshire speed limits are available to view upon request.

Changing the limit

Contact your Town or Parish Council (which may already have requested a limit or may wish to do so for you) or contact Highway Enquiries.

We will assess your request to see if it conforms to our current guidance. If it does we will assess and prioritise it but unfortunately there are many competing demands for our limited resources so even if the request conforms with policy, it may take several years to provide a speed limit.

Vehicle activated signs

Vehicle Activated Signs (VAS) are the electronic displays that flash up the speed limit, or other sign to give a clear warning of an approaching hazard. The signs are usually activated at a pre-set trigger speed by the approach of a vehicle. They alert only those who are driving above the speed limit or, if used on an approach to a hazard, too fast for the road conditions.

The signs appear to be effective in reducing speed, particularly of fast drivers who contribute disproportionately to the accident risk. Usually installed alone they can also be used to complement other speed-reduction measures such as traffic calming or speed cameras. Signs are currently operating at accident sites with externally funded signs at sites where there may not be a casualty history but there is a high degree of non-compliance with the speed limit.

What types of VAS are used in Oxfordshire?

VAS were first installed in the county in 2003. The majority relate to speed limits, however they can also be used to warn drivers of an approaching hazard such as a junction, crossroads or sharp bend. They are powered by mains electricity from a public power supply i.e. a street lighting column, or by solar panels.


Some signs are funded from our Casualty Reduction Programme. These are identified by our Road Safety Team and targeted largely to maximise potential casualty reduction, based on the reported five year injury accident history.

Other signs are funded from other budgets. These follow the general guidance within the VAS funding criteria document. The extent of provision will depend on their ability to support Local Transport Plan priorities and available funding.

Externally funded signs

Where there is no, or minimal casualty history but there is evidence to show a higher degree of non-compliance with the speed limit, a town or parish council and occasionally businesses, can fund VAS as low-cost accident prevention measure. The speed reduction from VAS enable communities to benefit from externally funded sites which would otherwise be beyond the resources of this Authority.