The Wyoming-led Connected Vehicle (CV) Pilot program has provided valuable work and feedback to Traffic Management Data Dictionary (TMDD) and the Society of Automotive Engineers (SAE) standards committees based on their implementations of CV standards in their deployment. Their work could be the basis for future editions of CV standards.
The CV Pilot program is sponsored by the USDOT Joint Program Office for Intelligent Transportation Systems (ITS) to pioneer the deployment of connected vehicle technologies in three U.S. locations: Tampa, Wyoming and New York City. A key goal of the CV Pilot project is for early deployers to work through initial deployment issues and provide lessons learned and feedback to the wider CV deployment community to aid future deployment efforts.
Wyoming provided feedback based on their work for three different standards. The first is the implementation of the TMDD using a JavaScript Object Notation (JSON) Representational State Transfer (REST) Application Programming Interface (API) rather than Extensible Markup Language (XML) and Simple Object Access Protocol (SOAP) as currently specified by the standard. The second is leveraging additional fields to the J2735 Basic Safety Message (BSM) Part II to support heavy vehicles properly. The last is the implementation of a new type of message, a Distress Notification Message (DNM).
The TMDD standards were created to support communication between traffic management centers across a region, so that data from the field can flow between centers easily. In Wyoming, information is collected by the traffic management center, and then it is made available to fleet management centers and surrounding DOT’s through TMDD. This data is also packaged into TIMs that are broadcast to connected vehicles. What Wyoming has modified is how the TMDD sends and receives messages, converting TMDD standard XML into JSON packages. Using JSON leads to an improvement in bandwidth, as JSON requires smaller data sizes to contain the same amount of data as XML.
The USDOT has not performed an analysis of the TMDD system Wyoming has implemented. Prior to pursuing an addition to the TMDD standard, this will require a deeper look. The Wyoming CV Pilot has offered their own resources to help create a JSON REST TMDD standard.
Previous research has been done on how to do conversions of the TMDD from XML to JSON, however that research
was missing some examples. The TMDD steering committee which decides what makes up the standard declined to
update the standard at the time leaving open the possibility of doing JSON Rest versions later, taking their
time to get it done right.
The Wyoming CV Pilot project has been invited to give a presentation to the TMDD steering committee about
moving to a JSON standard. Some questions remain to be answered, including whether Wyoming’s solution
maintains interoperability with other solutions, before creating a new standard based on their work.
The Wyoming CV Pilot will continue to provide feedback to SAE, who maintain the J2735 standard as they collect data on performance of the BSM Part II trailer data elements. Additionally, feedback provided by the WYDOT team will also be used as input to any future SAE efforts to develop performance requirements for heavy vehicle applications.
Finally, Wyoming has created a Distress Notification Message (DNM) a message specifically for when a vehicle is in a distress situation. There is no structure for a DNM in J2735, it’s a structure proposed by Wyoming. According to the WYDOT Interface Design Document (ICD): “Distress information is a high priority message loosely based on the mayday broadcast defined in SAE J3067, but has the content of the TIM defined in SAE J2735.” The Wyoming CV Pilot concept of Distress Notification is illustrated below.
Distress Notification concept diagram (Source: WYDOT)
The DNM will be triggered either when the vehicle can sense a distress situation or when the driver hits a panic button. The Wyoming CV Pilot project has demonstrated the DNM to USDOT and is providing operational scenarios, user needs, requirements and design to the standards committees.
Through this work the Wyoming CV Pilot project is providing valuable feedback to ensure smooth and safe future deployments of CV technologies across the country.
