Connected and Automated Vehicles Investment and Smart Infrastructure in Tennessee Part 3: Infrastructure and Vehicular communications: From Dedicated Short-Range Communications to Cellular Vehicle-to-Everything

This report aims to support the Tennessee Department of Transportation's decisions about vehicle and infrastructure communication technologies. The transition from Dedicated Short-Range communication (DSRC) V2X to Cellular Vehicle to Everything (C-V2X) is explored using USDOT guidance on relevant issues and presenting the results of experimentation in Tennessee and the potential pros and cons. DSRC V2X technology has been planned at traffic signal in Tennessee, e.g., 152 Roadside Units (RSUs) were planned by TDOT using DSRC V2X and Bluetooth combination units in the I-24 smart corridor. Similarly, many pilot programs and testbeds around the nation have deployed DSRC V2X technology and are now impacted by the Federal Communication Commission's (FCC) ruling on opening safety band. The implication is that DSRC V2X deployments (and future deployments) should migrate to C-V2X. Notably, dual-mode RSUs are available along with LTE C-V2X. The transition can be done by working with vendors, but surely this involves more than swapping DSRC V2X devices with LTE C-V2X devices. Complicating the migration to C-V2X is TDOT's role in traffic signal operations and maintenance, which is limited to funding and designing/construction of traffic signals, but local agencies operate and maintain signals. Hence, local agencies will work with TDOT to operate and maintain C-V2X technology. Moreover, C-V2X technologies are not widely tested-interference by unlicensed devices and channel congestion can adversely affect safety-critical applications. Given the substantial uncertainties in transitioning to these technologies, TDOT's discussion with IOOs about the operation and maintenance of C-V2X may have to wait for the resolution issues, while TDOT can invest in experimentation with dual-mode devices. Recommendations are provided about dual-mode devices, CAV data, and needed research and testing.