Abstract
In this thesis, a method of real time traffic signal instrumentation is introduced and described. Current practices of cabinet instrumentation methods require physical electrical connections to each traffic signal being instrumented. These methods are labor intensive to install and some state governments require a certified technician due to the 120VAC signals used. The new method obtains information concerning the traffic signal status by monitoring communications on the Synchronous Data Link Control (SDLC) network between existing equipment within NEMA TS2 traffic cabinets. Using the SDLC interface reduces the risk associated with high voltage and allows for a more time efficient installation.
A case study is presented that demonstrates the proposed SDLC--based instrumentation method with an Advanced Accessible Pedestrian System (AAPS). Comparisons between the proposed SDLC method and current methods of traffic signal instrumentation showed that the decoding time of sensing a traffic signal state in the new method is more consistent with devices already in the traffic cabinet. This new method can be used in other traffic signal system applications such as an SDLC Interface Device or a device to log the state of different input/output channels at the signalized intersection.