Today's in-vehicle navigation systems using the standalone Global Positioning System (GPS) can provide position information with an accuracy of 10-20 meters, which may be improved to 1-3 meters if standard Differential GPS techniques apply. This accuracy, however, still does not meet the strict requirements for some road safety functions. Examples include Intersection Collision Warning, Forward Collision Warning, Lane Change Warning, Blind Spot Warning, which require horizontal errors within 0.5 to 1.0 metres with high reliability, eg, 99.99%, approximately equivalent to RMS accuracy of 0.1 to 0.2 meters. In addition, some safety applications need highly accurate and reliable relative position information between vehicles.

The presentation explores the applications of precision GNSS in Intelligent Vehicle (IV) systems for road safety purposes. The accuracy and integrity requirements for the vehicle absolute and relative positioning are examined, along with the latency and availability requirements for wireless communications between vehicles and vehicles to base stations. The presentation also discusses the performance benefits of multiple frequency GNSS signals offered by the next generation GNSS systems for meeting the above positioning requirements. The advantages and feasibility of using dedicated short-range communications (DSRC) to transmit RTCM messages between vehicles and vehicle to base stations will be studied. Results from GPS experimental data collected on two high-speed vehicles and one base station will be analysed to demonstrate the performance potential of Real Time Kinematic positioning techniques for vehicular safety applications.