Section: D.5 Intelligent transport systems – infrastructure backhaul D.5.0 General
Content: Intelligent Transport Systems (ITS) embrace a wide variety of communications-related applications that are intended to increase travel safety, minimize environmental impact, improve traffic management, and maximize the benefits of transportation to both commercial users and the general public. Over recent years, the emphasis in intelligent vehicle research has turned to co-operative systems, in which the traffic participants (vehicles, bicycles, pedestrians, etc.) communicate with each other and/or with the infrastructure. Cooperative ITS is the term used to describe technology that allows vehicles to become connected to each other, and to the infrastructure and other parts of the transport network. In addition to what drivers can immediately see around them, and what vehicle sensors can detect, all parts of the transport system will increasingly be able to share information to improve decision making. Thus, this technology can improve road safety through avoiding collisions, but also assist in reducing congestion and improving traffic flows, and reduce environmental impacts. Once the basic technology is in place as a platform, an array of applications can be developed. Cooperative ITS can greatly increase the quality and reliability of information available about vehicles, their location and the road environment. In the future, cars will know the location of road works and the switching phases of traffic lights ahead, and they will be able to react accordingly. This will make for safer and more convenient travel and faster arrival at the destination. On-board driver assistance, coupled with two-way communication between vehicles and between vehicles and road infrastructure, can help drivers to better control their vehicle and hence have positive effects in terms of safety and traffic efficiency. An important role in this plays the so-called road side units (RSUs). Vehicles can also function as sensors reporting weather and road conditions including incidents. In this way, cars can be used as information sources for high-quality information services. RSUs are connected to the traffic control centre for management and control purposes. They broadcast, e.g., traffic light information (RSU vehicle) and traffic information from the traffic-control centre (TCC) via the RSU to the vehicles (TCC RSU vehicle). RSUs also collect vehicle probe data for the traffic control centre (vehicle RSU TCC). For reliable distribution of data, low-latency and high-capacity connections between RSUs (e.g. traffic lights, traffic signs, etc.) and the TCC are required. This type of application comes with rather tight end-to-end latency requirements for the communication service between RSU and TCC (10 ms), since relayed data needs to be processed in the TCC and, if needed, the results are forwarded to neighbouring RSUs. Also, the availability of the communication service has to be very high (99,9999%) in order to compete with existing wired technology and in order to justify the costly deployment and maintenance of RSUs. Furthermore, due to considerably large aggregation areas (see clause D.5.1), considerable amounts of data need to be backhauled to the TCC (up to 10 Mbit/s per RSU).