Road Weather Warning
Another application of mobile ITS is the management of adverse weather situations such as reduced visibility due to seasonal fog. It is widely agreed that visibility and other roadway weather situations like surface water can adversely affect driver behaviour. Portable, easily deployed ITS applications play an integral role in the operational framework for roads where adverse weather conditions have a direct impact on motorists. Employing mobile ITS technology along a designated route can have a dramatic roadside impact, informing motorists of adverse weather conditions, such as low visibility due to fog and surface water thickness, and the subsequent effect on braking distance. A simple real time warning system can dramatically affect driver behaviour and actively encourage motorists to reduce speed by providing timely information on the situation further downstream.
Quite often, visibility is worst on roads which do not have a suitable fog detection and warning system. The use of mobile VMS and speed sensors for pilot projects enables road engineers or consultants to choose the best location based on specific site needs. VMS can be placed upstream of existing weather stations equipped with visibility sensors. Fog sensors can even be mounted on traffic sensor trailers or VMS. The distances between signs and warning devices should be based on road speeds or alternative routes available and be sufficiently in advance to allow drivers time to take the appropriate action. For example, if the normal action is to just reduce speed, then the advance warning distance is less. This can all be determined on a trial basis using Mobile VMS and JamLogicTM software, which supports information from visibility or water film thickness sensors. The addition of mobile speed sensor trailers provides a secondary method to detect a problem and also monitors traffic flow during a fog / surface water event to help traffic control engineers tweak the logic applied to better tune the system. The report following a trial can then be used as a cost efficient model to evaluate whether motorists reduce their speed as a result of being informed of road conditions and if effective, to promote deployment of permanent ITS technologies.