8.4 Materials
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8.4.1 There is an array of choices facing the designer when selecting materials for traffic calming measures, and a number of factors influence this choice.
These range from local environmental considerations, through technical performance and maintenance
issues, to financial and purchasing policy factors.
To this range of factors must be added the needs of vulnerable road users, including motorcyclists.
The choice of materials can have a huge impact on the utility and safety of a traffic calming scheme from the rider’s viewpoint. Particular issues to consider include:
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The use of block paving or stone setts, including on speed tables and raised junctions.These often have poor skid resistance, especially when wet.
They are hard to maintain, with displaced blocks and alternative reinstatement materials offering uneven and unpredictable surfaces for motorcyclists.
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The use of bitumen to seal cracks and reinstatements.
This material has very low skid resistance in wet conditions, yet is routinely used to seal the joints in traffic calming measures, notably speed cushions. Alternative materials are becoming available (FEMA 2004).
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The use of white thermoplastic on traffic calming measures; for example white triangles used to highlight humps are mandatory, but can cause problems when:
• The material used has insufficient skid resistance. Markings are often at the centre of a lane, just where the wheel tracks of motorcycles will pass.
• High traffic levels or poorly specified material can cause them to fade quickly, making a bitumen-based measure hard to distinguish against the road surface, especially at night.
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Transverse bars, rumble strips and “dragon’s teeth” markings on the approach to gateways and other traffic calming measures are often in the braking zone for road users. If the materials do not provide suitable skid resistance or if they present a series of vertical displacements they can constitute an added hazard for motorcyclists.
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The potential to use collapsible or frangible street furniture, especially in locations that could conceivably be in the path of a falling rider. |
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