Speed Humps 

Speed humps are perhaps the oldest form of traffic calming. There are now a variety of different types including speed cushions which can be used, providing there is enough road width, to provide a smoother passage for heavy goods vehicles, buses and emergency vehicles.

Whilst effective they can be intrusive to the environment and can raise strong local feelings.

Effectiveness
The most effective form of speed reduction. Speed reductions of around 10 mph can be expected (depending on the initial speed).

Examples in Cambridgeshire

• The Offords
• Cottenham
• Papworth Everard
• Storey's Way, Cambridge
• Norwich Road, Wisbech
• High Street, Chatteris
• Gamlingay

Best suited locations
Speed humps are well suited to low speed residential roads with small numbers of HCVs. On busier roads they can be used where speed reduction is essential and there is no other effective measure.

Traffic Islands

Traffic islands are a useful and cost effective way to provide some carriageway narrowing, to focus the attention of drivers and to provide crossing facilities for pedestrians.

However, the road has to be wide enough to allow large vehicles past and local widening into the verge may be required.

Effectiveness
Not very effective as a speed reduction measure on its own (2-3 mph) but better as part of a more comprehensive scheme. Can be useful in providing pedestrian crossing facilities if correctly positioned. Can also help to enforce lane discipline.

Points to note

• Can prove difficult for cyclists as they may be 'squeezed' between a large vehicle and the kerb. With the right carriageway width this can be addressed effectively by road markings
• Mandatory signing and lighting are required. These can be visually intrusive
• Parking should be avoided within 20m either side of the feature. This may mean formal restrictions and could cause difficulties particularly if there are local shops.
• May restrict access to private drives

Examples in Cambridgeshire

• Hilton
• The Offords
• Ramsey
• Elm
• Fen Ditton

Best suited locations
Can be a useful part of any speed reduction scheme if suitably located.

Mini Roundabouts

Mini roundabouts are often used as part of traffic calming/speed reduction schemes. However, the highway condition needs to be right. As a general principle due care needs to be taken in giving priority to vulnerable road users - generally this means cyclists or pedestrians but in this case it is those entering mini roundabouts from the minor arm.

Mini roundabouts can prove dangerous for cyclists unless vehicle speeds are reasonably low (under 30 mph).

Effectiveness
Can be very effective, as part of an overall traffic calming scheme but needs reasonable minor leg flow.

Points to note

• Statutory requirement to have street lighting
• Can be environmentally intrusive
• Cyclists need careful consideration
• Can present visibility problems for pedestrians and drivers at side roads
• In restricted spaces HCVs may have to run over the central dome giving rise to noise

Examples in Cambridgeshire

• Bassingbourn
• Cambridge, Arbury Road
• Chatteris, High Street
• Cottenham
• Eaton Socon

Best suited locations
As part of a more extensive speed reduction scheme with a reasonable flow on the minor arm.

Thumps and Rumble Strips 

Thumps are effectively very small road humps (height 40mm). Their purpose is more to remind drivers that they are in a road where speed should be reduced rather physically stopping them. Rumble strips have the same effect but are even smaller.

 
Effectiveness
It is not yet clear how effective these measures are but a speed reduction of around 3 mph is probably likely. They are often installed in association with more extensive schemes. The effectiveness of rumble strips tends to reduce over a period of time.

Points to note

• Thumps are less noisy but less effective than conventional road humps. Street lighting must exist.
• Rumble strips can be installed outside a speed limit, but can be noisy and are not recommended within 200m of residence.

Examples in Cambridgeshire

Thumps

• Fenstanton
• Clarkson Avenue, Wisbech

Rumble Strips

• Linton

Best suited locations
Thumps would be suitable as part of a low level traffic calming scheme where great speed reductions were not required.

Rumble strips would be appropriate on faster roads in rural areas on the approach to a speed limit reduction.

Horizontal Deflection

There are three main types of horizontal deflector features:
Nibs/sheltered parking
Chicanes and narrowings
Give way features (priority narrowings)

Effectiveness
Priority narrowings are very effective at the point of construction (vehicles may be brought to a halt) but speeds beyond the feature will increase. Nibs and chicanes can be affective when used as part of a more extensive scheme.

Points to note

• Particular care needs to be taken in installing give way features as they are not suitable for high speed or heavily trafficked (greater than 6,000 vehicles per day) roads. Safety Audit approval is necessary to ensure they do not become an accident risk. A reasonably balanced two-way flow is also required.
• With all horizontal deflection consideration needs to be given to the requirements of large vehicles. They would be unsuitable for the abnormal load routes.
• Cycle bypass facilities are often required.

Examples in Cambridgeshire

• Cottenham
• Eltisley
• Eaton Socon
• Fen Ditton
• Fulbourn
• Ramsey
• The Offords

Best suited locations
Give way features can be used at entrance to village but the road conditions must be suitable.
Nibs and chicanes are useful as part of more extensive speed reduction.

Gateway Features 

The idea of a gateway feature is to emphasise to drivers that they are entering an area where the needs of the adjacent community are as, or more, important than the convenience of through traffic. A gateway feature might include:

• Red surfacing with roundel
• Verge structures such as walls, gates or post and rail fences
• 30 mph sign incorporated with village name plate
• Countdown markers
• Central refuge

Effectiveness
Generally quite effective initially (4-5 mph reduction) but evidence suggests that speeds tend to creep up again after a period of time.

Points to note

• Gateways provide a visual effect of narrowing the carriageway and therefore vertical features are necessary
• Roundels and countdown markers require DETR approval
• Red surfacing can discolour and fade, particularly if there is a high level of HCVs

Examples in Cambridgeshire

• Fordham
• Hilton

Best suited locations
Good in villages where speeds are not much greater than 40 mph. For higher speeds would need to form part of a more comprehensive scheme.