The Design of Reliable Protocols for Wireless Traffic Signal System

Electronic traffic signal has the advantage of being easily visible to machines. It is expected to augment the traditional traffic light system in future intelligent transportation environments, where intelligent vehicles interact with each other and with traffic systems and give informed advisories to drivers. One problem with wireless signals is that they are essentially omnidirectional. Even if one uses directional wireless signaling source, it is not clear how any recipient of a signal can reliably determine whether the signal is meant for him or her, in the presence of signal reflections. In this paper, we present a basic electronic traffic signalling protocol framework and two reliable protocols for intersection traffic signal and stop sign signal. These protocols enable recipient vehicles to robustly differentiate the signal's designated directions despite of potential threats (confusions) caused by reflections. We demonstrate how to use one of the protocol to construct a sample application: a red-light alert system. We also address potential inconsistency threats caused by the uncertainty of location system being usedand discuss means to handle them.