8.3.1 One of the first questions facing the designer of a traffic calming scheme should be whether to use physical traffic calming measures or not. More subtle changes to the environment, possibly using existing environmental features and taking a holistic approach to the street scene may be more appropriate. It may be possible to adopt a psychological approach to traffic calming methods by modifying the built environment in such a way as to create a “negotiated space” for all road users, with a concomitant reduction in speed, enabling the reduction or even removal of the need for vertical traffic calming features.
8.3.2 The choice of what type of physical measures to use is normally influenced by a number of factors, including: accident records, traffic volume; pedestrian activity; target speed; the presence of bus routes; the needs of emergency services, sensitivity of the local environment, the views of local residents and budget.
Many motorcyclists prefer speed cushions that give the option of riding between the speed cushions rather than over them.
This does not negate the measure; the act of aligning a motorcycle to pass through a small gap between speed cushions will bring about some reduction in speed, although it may fall short of the target speed for the scheme.
Useful publications in this area include Home Zone Design Guidelines (IHIE 2002) and Traffic Calming Techniques (IHT/CSS 2005) and relevant Traffic Advisory Leaflets available from the Department for Transport (DfT).
Location of traffic calming measures
8.3.3 A major problem facing the designer of traffic calming schemes is choosing the location of the measures.
The needs and vulnerabilities of motorcyclists should be accounted for along with all the other factors influencing this process. Some important issues are:
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Vertical traffic calming measures should not be located anywhere a motorcyclist will need to brake or changing direction. Ramps for raised junctions should begin far enough back so that the motorcycle negotiates the ramp in a straight line.
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The design of the scheme should include adequate warning signs, both permanent and temporary, warning of the new road layout ahead. Consider using on-site publicity prior to installing the traffic calming measures. Ensure any temporary signs are removed not later than three months after the completion of the scheme.
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Whenever possible a non-vertical speed reducing feature should be used at the entrance to a traffic calming scheme.
Since changes in the regulations affecting traffic calming scheme design, some schemes have appeared that start with a speed hump or cushions.
Without some form of speed reducing feature, there is always the risk that a motorcyclist will unintentionally hit the first vertical measure at speed. For a car driver, this could imply an uncomfortable bump. For a motorcyclist, the implication could be serious injury.
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A commonly used non-vertical speed reducing feature in traffic calming schemes is the mini-roundabout. Without careful design, motorcyclists, like other vulnerable road users, can suffer disproportionate risk at these junctions. Particular points to bear in mind include:
• Adequate skid resistance of the mini-roundabout arrow markings.
• Most junction designs are checked to make sure that larger vehicles’ swept paths can be accommodated. Motorcycles making tight right turns at miniroundabouts can have stability problems, especially if the turn is more than 90°.
• Make sure there is adequate advanced warning of the junction type.
• Ensure adequate visibility; using a mini-roundabout because there is insufficient visibility for a priority junction is rarely a safe option for any road user.
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The design of horizontal schemes, often called chicane schemes, should allow for the fact that motorcyclists on lower-powered machines tend to ride near the kerb.
The build-outs often associated with these schemes can pose significant risks:
• They can catch riders unaware, leading to collision. This is especially a problem when a scheme is recently constructed. Build-outs should be conspicuous.
• They force motorcyclists to move to the centre of the road or even, in priority working schemes, into oncoming traffic, much of which is unwilling to give way to a motorcycle, especially a smaller machine.
• The use of low over-run areas as build-outs can cause stability problems if a rider clips the edge.
The standards permit an up-stand of no more than 15mm, but even this can cause problems to the rider of a smaller machine when turning.
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Islands or refuges used to reduce the width of the road should be conspicuous, allowing motorcyclists to position themselves correctly in advance, avoiding late and sudden changes of direction.
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Where bicycle bypasses are provided around traffic calming measures, these should be narrow enough to discourage use by motorcycles.
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Always ensure the location of traffic calming measures does not lead to poor drainage; standing surface water could compromise motorcycle safety, especially in freezing conditions.
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Humps and speed cushions should be located 10-15 metres away from junctions to allow riders to turn out and to pass over them vertically.
This should be balanced against pedestrian desire lines where flat-topped humps are being specifically installed as crossings. |
Lighting
8.3.4 Most traffic engineers understand that street lighting is a specialised subject requiring an increasingly sophisticated approach and comprehensive knowledge of the types of light sources available and the best places to use them. It is of vital importance that the night-time safety and performance of traffic calming measures are not compromised by inadequate street lighting.
Motorcycle head lamps are typically less bright than those of other vehicles, making good lighting of traffic calming measures an important factor in making the scheme safer.
Obviously the first point of contact will be the local authority street lighting team; if this is not possible, then the Institution of Lighting Engineers (ILE) can provide advice on the technical aspects of scheme lighting to suit all road users, including motorcyclists.
The ILE has published a technical report called Lighting for Traffic Calming Features (ILE 2002).
Particular issues to bear in mind are:
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The scheme should be evenly illuminated, with particular attention paid to traffic calming measures that alter the normal road alignment, for example build-outs and chicanes. |
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The lighting should provide good colour rendering, especially where colour is an integral part of the scheme. |
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