Change a speed limit

Our approach to 20mph Speed Limits

Buckinghamshire Highways follows Department of Transport (DfT) guidance when setting local speed limits.

20mph speed restrictions may be suitable for streets that are primarily residential and in either 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.

Successful 20mph zones and 20mph speed limits generally should be self-enforcing, i.e. the existing conditions of the road lead to a mean traffic speed broadly compliant with the desired speed limit. To achieve compliance there should be no expectation on the police to provide additional enforcement beyond their routine activity, unless this has been explicitly agreed.

There are two types of 20mph speed limit:

20mph limit; this is a signed speed limit with entry signs and repeater signs.

20mph zone; this is an area of traffic calming with entry signs only.

20mph Limit

National DfT guidance ‘Setting Local Speed Limits’, 2013, states:

“Research into signed-only 20mph speed limits shows that they generally lead to only small reductions in traffic speeds. Signed-only 20mph speed limits are therefore most appropriate for areas where vehicle speeds are already low. This may, for example, be on roads that are very narrow, through engineering or on-road car parking. If the mean speed is already at or below 24 mph on a road, introducing a 20mph speed limit through signing alone is likely to lead to general compliance with the new speed limit.”

20mph Zone

A 20mph zone is slightly different and would usually need to feature a series of traffic calming measures (though these could be existing features within the highway such as bends, narrowing). These features would aim to reduce speeds close to 20mph and therefore would aim to gain support from TVP. The cost of installing traffic calming can be expensive – for example build-outs or speed cushions, which both require adequate lighting. Zones usually cover a number of roads.

How the process works

Thames Valley Police (TVP) and Buckinghamshire Council currently only support a 20mph limit on roads without traffic calming where mean speeds are at or below 24mph.

There is a charge for this service, which would need to be met by the Parish to Town Council. The proposal to undertake the assessment must be supported by the Buckinghamshire Council elected Member for that ward.

Each supported request for Buckinghamshire Highways to install 20mph limits is assessed individually against DfT guidance. Fundamentally if speeds are already low (i.e. below 24mph) then a 20mph limit may be appropriate.

If average speeds are higher than 24mph then then a 20mph limit is unlikely to be successful without traffic calming. The cost of the traffic calming is often the reason why these limits are not progressed.

• Does the Parish Council/Town Council/External Participating Stakeholder agree to fund & support?

If yes:

• Do all local Buckinghamshire Council Ward Members support the request?

If yes:

• A request is made to Buckinghamshire Highways for a Speed Limit Assessment (from £1,075) and Speed Survey(s) (£504.70 each).

If the request is agreed:

• Does the Speed Limit Assessment support a 20mph signed only speed limit?

If yes:

• Do all local Buckinghamshire Council Ward Members support it?

If yes:

• Obtain Community Board and Buckinghamshire Council councillor approval for feasibility and works delivery*. Secure minimum 50% external match funding from others (e.g parish).
  *Staff, capacity and financial resource will need to be available.

If this is obtained:

• Proceed with the legal (statutory) consultation with the proposals to implement a new Traffic Regulation Order and implement posts and signs. Typical costs can vary depending on scheme but are circa £10,000 to £50,000.