Loss of control through skidding can be a significant factor in many crashes (especially when the road is wet). Particular attention should be paid to the skidding resistance properties of the carriageway surface at areas where braking commonly occurs such as on the approaches to intersections, roundabouts, pedestrian crossings and on bends or steep grades.
Poor skid-resistance can occur when the road surface becomes worn (aggregate becomes polished) under the action of traffic, or temporarily if there is a build-up of oil or debris on the road or if road drainage is poor. There are two main options for treatment of low skid resistance:
Retexturing This method includes the mechanical reworking of the existing surface to improve its frictional characteristics and therefore the resistance to skidding. Typically involves the removal of material from the road surface. Methods include diamond grooving, shot-blasting, bush hammering, high velocity water blasting.
Resurfacing These include relatively low cost thin surfacing treatments that not only improve the surface texture and resistance to wet road skidding but can also seal the surface against water penetration and arrest disintegration of the existing road surface.
Surface dressing for example, uses a bitumen emulsion sprayed onto the road surface followed by a layer of chippings with a high Polished Stone Value (PSV).
High friction surfacing (HFS) utilizes refractory grade calcined bauxite, an extremely hard wearing aggregate (with a high PSV) that provides and maintains good skid resistance. HFS systems may be based on either thermoplastic (hot-lay) or thermosetting (cold-lay) resin binders.
Porous friction course is a very permeable asphalt layer with continuous voids to accommodate runoff of low to moderate intensities of rainfall. The material improves skid resistance at high traffic speeds, limit water sprays, and reduce the possibility of aquaplaning.
- Improved safety for roads where a lot of crashes happen, especially in wet weather.
- Can help to prevent both rear-end and run-off road crashes.
- Resurfacing provides an opportunity to fix other road surface problems, such as crossfall and rutting.
- Provides the opportunity for adding or replacing road surface delineation such as painted markings or reflective road studs.
- Can extend life of pavement surface.
- Retexturing has environmental benefits over some traditional hot mix asphalt resurfacing. Typically lower cost and lower energy solution.
- Often quick and repeatable treatments with low traffic disruption. In most cases roads can be driven on immediately after application.
Low to medium
5 years - 10 years
Potential casualty reduction