We all take road markings for granted - for everyone road markings are the road at night. Without them night time driving on rural roads would be chaotic. But that is exactly what is happening each time it rains. Road markings disappear at night as soon as they are covered with water. In Australia water downpours at rates of 10+ mm/hour are not unusual and this effectively renders the visual message from the white lines on the road surface useless. Conventional glass beads on the road markings are sized between 150-650 microns. Whilst beads of this size are adequate for dry night conditions, a rainfall rate of 2-5 mm/hour submerges them. A new generation of glass beads - Visibead Safety Marking Spheres - have been developed which remain reflective when wet, even at rainfall rates of 20 mm/hour. Retroreflectivity standards are presently being developed on an international level to cope with the needs of road users in wet and dry conditions at night. The paper discusses these developments and relate them to requirements in Australia. Trials have been taking place using Visibeads with various long-life road marking binders around the world and in Australia. Data is presented using field studies in various locations which conclusively show the benefits of using Visibead road marking systems. The paper also gives details of the latest developments in equipment - laser retroreflectometers - which have the ability to measure road marking reflectivity under rainfall conditions and also when mobile (A).
Samenvatting