A Railway Collision Avoidance System Exploiting Ad-hoc Inter-vehicle Communications and Galileo

The introduction of the European global navigation satellite system GALILEO allows also for a modernization of automatic train control technology. This is advisable because of the still enormous amount of collisions between trains or other kinds of obstacles (construction vehicles, construction workers, pedestrians), even if comprehensive and complex technology is extensively deployed in the infrastructure which should help to avoid such collisions. Experiences from the aeronautical Traffic Alert and Collision Avoidance System (TCAS) as well as the maritime Automatic Identification System (AIS) have shown that the probability of collisions can be significantly reduced with collision avoidance support systems, which do hardly require infrastructure components. In this article, we introduce our “RCAS” approach consisting only of mobile ad-hoc components, i.e. without the necessity of extensions of the railway infrastructure. Each train determines its position, direction and speed using GALILEO and broadcasts this information, complemented with other important information such as dangerous goods classifications in the region of its current location. This information can be received and evaluated by other trains, which may – if a potential collision is detected – lead to traffic alerts and resolution advisories up to direct interventions (usually applying the brakes). STATE OF THE ART IN TRAIN CONTROL Today the safety of railway operation is mainly ensured by the interlocking which sets and locks the train route. All track elements are set and locked in the correct position, before signals are set to green. The trains are equipped with the onboard part of the train control system which triggers automatically a braking if the train passes a signal at danger. The safety of railway operation depends on the correct operation of the interlocking and the train control system. Human errors [2] lead to most of the accidents [6]. Nevertheless the safety technology has some important drawbacks: • Trains which are not equipped with onboard train control systems may pass signals without problems. Typical trains of this kind are construction trains, foreign trains or groups of wagons. • A malfunction in the railway control centre or in the onboard safety system can prevent monitoring entirely.