Successful Communication between Roadside Unit and Standard Traffic Controller

The Connected Vehicle Pilot (CV) program, sponsored by the US Department of Transportation (USDOT) Joint Program Office for Intelligent Transportation Systems (ITS JPO), recently demonstrated the ability of a CV Pilot Roadside Unit (RSU) to interact with a standard signal controller using standard messages.

In late January, USDOT hosted a face-to-face meeting at the Turner-Fairbank Highway Research Center (TFHRC) in McLean, VA among the three CV Pilot teams - New York City Department of Transportation (NYCDOT), Wyoming Department of Transportation (WYDOT), and the Tamps Hillsborough Expressway Authority (THEA) - and their contractors.  The three teams discussed approaches to ensure that the hardware and software they are developing will be interoperable.

Going beyond these discussions to test actual equipment, the THEA team brought an RSU matching those installed and operating at 40 intersections in Tampa as part of the Tampa CV Pilot project.  On January 22, 2018, the THEA contractor connected the RSU to a 3rd party Advanced Transportation Controller (ATC) at the TFHRC.  After the RSU network address was programmed into the ATC, the RSU successfully received messages from the ATC and broadcast Signal Phase and Timing (SPaT) and intersection geometry (MAP) messages over the air.  In an actual deployment, these SPaT and MAP messages will be used by equipped vehicles for crash avoidance and mobility and ecology-related applications such as Red Light Violation Warnings, Signal Priority Requests, and Eco-Approach to Signalized Intersection.

Since the message that the TFHRC ATC sent to the RSU was a standard Traffic Signal Controller Broadcast Message (TSCBM), this “Plug and Play” success suggests that tens of thousands of intersections controlled by ATC and NEMA TS2USDOT V2I Hub standard equipment that use the TSCBM could interoperate with RSUs such as those being developed for the CV Pilot deployments. Since October 2016, systems engineering efforts of all three CV Pilot teams have included the TSCBM in their joint list of interfaces necessary for nationwide interoperability.

The figure at left illustrates how the ATC controls the traffic signal, and sends TSCBMs to the RSU. The RSU then sends SPaT and MAP messages to the Onboard Units (OBUs) of equipped vehicles, to pedestrians, and to other devices via Dedicated Short Range Communications (DSRC) and WiFi.

The TSCBM was developed under FHWA Contract in 2011 and is published as Table 3-4 of the Vehicle-to-Infrastructure (V2I) Hub Interface Control Document (ICD) on the USDOT/FHWA Open Source Application Development Portal (OSADP) . The OSADP also includes open-source code that reads the TSCBM for test purposes.