INFORMATION AND CONTROL SYSTEMS FOR ROAD TRAFFIC. PART III: TECHNICAL SURVEY AND FUTURE DEVELOPMENT

This report mainly deals with equipment and systems for driver information and traffic control. Traffic control systems need data from different kinds of equipment that measure, transfer and prepare the data. Detectors such as inductive loops, magnetometers and ultrasonic sensors automatically measure traffic flow, speed, presence and density on important road sections. There is a need for reliable communication systems for transfer of data from detector to control system and to information display. Suitable techniques are cables, fiber optics, optical transmission, magnetic fields and radio waves. Information to drivers can be transmitted via equipment on the road or in the vehicle. Changeable message signs are used for road condition information. The current changeable message signs fall into three categories: mechanical, light source and electromechanical. Different types of radio, mobile telephones and internal visual communication systems are examples of vehicle-based equipment. Visual communication systems are used in connection with route guidance systems. Pre-warning systems aimed at preventing accidents must have very short detection and transmission times. A suitable method to inform drivers on high speed roads seems to be road condition signals. To improve flow conditions in networks with signalized intersections it is desirable to co-ordinate the signals. Co-ordination of signals has resulted in an average reduction in travel time of 25% compared to older pre-timed signals. (TRRL)