Somerset County Council

Speed limits


Traffic calming is a way of controlling the speed of vehicles. As the highway authority, we make physical alterations or implement traffic management measures.

The aim of traffic calming is to improve safety, reduce speed disturbance and anxiety, and enhance the environment.

You can contact us to request information about new or existing traffic calming measures.

There is a series of advisory leaflets to assist and inform about improvement scheme submissions on our Small Improvement Schemes page. 

The most common type of traffic calming measures are:

Speed humps and platforms: These are probably the most effective form of traffic calming available for controlling vehicle speeds. Their effectiveness relies on creating a vertical deflection to vehicles as they pass over them which in turn transmits discomfort to the drivers and other vehicle occupants. On traffic sensitive routes, such as bus routes, speed cushions are used in preference to speed humps. The cushions allow larger vehicles, such as buses, emergency vehicles and HGVs, across them with minimal deflection so giving a smooth ride to the occupants, but still reducing the average speeds of private and small vehicles. Here are descriptions of the various types:

  • Round Top: This type of hump has a rounded profile, typically 3.7 metres long. 

  • Flat Top: This type of hump consists of an upward slope followed by a flat section, minimum length of 2.5 meters, and a downward slope. It can be made flush with the footway to provide a convenient crossing place for pedestrians. Another version of this type of hump, often used within housing estates, is the 'speed table' or 'platform' that consists of a flat top hump over an entire road junction.

  • Speed Cushion: This type of road hump occupies part of the traffic lane and usually 2 are installed across the road. The spacing is such that cars will be slowed, but larger vehicles such as buses and emergency vehicles will suffer little inconvenience. Size and shape can differ but 1.6m x 3.1m is typical although larger sizes can be used without any adverse effects on buses and emergency services. However, measures may need to be considered to deter random parking in the area of the cushions, which could otherwise create problems for buses attempting to drive over the cushion, or prevent cyclists and motorcyclists from using the nearside gap between the kerb and the cushion. This type of hump will have little effect on the speed of heavy vehicles or motorcycles.

  • Raised table junctions: These are normally installed as part of a road hump scheme and the vertical deflection includes the whole junction. 

  • Chicanes: These can be effective in reducing vehicle speeds on wider roads. Although chicane designs vary considerably they generally consist of 2 types:
    (a) single lane working made up of kerb buildouts, staggered on alternate sides of the road, narrowing the road so that traffic from one direction has to give way to opposing traffic;
    (b) two-way working, using kerb buildouts to provide deflection, but with lanes separated by road markings, or a central island. The single lane working chicane relies heavily on opposing traffic flows to influence speeds. However, the need to accommodate long/large vehicles generally ensures that smaller vehicles, such as cars and motorcycles, can often negotiate the chicane at higher speed. Chicanes are often very difficult to accommodate where there are regular private drives and accesses.

Roundabouts and mini-roundabouts: Where a small central island is used, this can influence speeds. The roundabout geometry should make sure there is adequate deflection to slow vehicles down on approaching the roundabout and prevent them accelerating away too quickly as they exit. Mini-roundabouts should only be considered where they create a 3 arm mini-roundabout and the central island should be raised for better visibility. Double mini-roundabouts can be used at offset 4 arm junctions if there is sufficient offset of the minor roads.

Coloured surfacing: This can be used to heighten driver awareness. Anti-skid surfacing can be used to heighten driver awareness or give particularly good resistance to skidding.

Gateways: These are features at the entry to villages and towns, generally where the speed limit begins, to increase driver awareness.


Contact: Roads and Transport Team
Phone: 0300 123 2224
Opening Hours: Monday 8am to 6pm, Tuesday to Friday 8.30am to 5.30pm, Saturday and Sunday closed.

If there is an urgent problem outside these hours and it is a risk to public safety please phone the police on 101.

If you need to visit a highway area office you can find the address of your local office here.

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