Virtual Traffic Lights: A Robust, Practical, and Functionally Safe Intelligent Transportation System

The latest advancements in intelligent transportation systems (ITSs) increasingly rely on wireless vehicle-to-vehicle (VTV) and vehicle-to-infrastructure (VTI) communications to manage traffic flows at intersections dynamically. A prominent example is virtual traffic lights (VTLs), which use only VTV communications and which have been shown to have the potential to increase traffic flows and reduce emissions significantly. Two key issues that can affect the adoption of desirable ITS solutions like VTLs are functional safety and the management of a move from a vehicle fleet not equipped with VTLs to a vehicle fleet completely equipped with VTLs. For the first issue, the first model-driven engineering-based modeling and verification technique for ITSs is proposed. This technique can be used to prove functional safety with 100% coverage. Through the use of this technique, it is shown that although VTLs are safe under normal circumstances, they are very fragile when they face unlikely, but not impossible, exceptional circumstances. For the second issue, an extended algorithm called VTL+ is proposed. VTL+ uses additional VTI communication with the existing infrastructure to enable effective and safe traffic flow during the VTL transition phase. It is also found through static analysis that VTL+ is more robust and more feature rich than VTLs.