Connected and automated vehicle (CAV) technology is expected to significantly improve transportation systems by providing benefits in mobility, safety, and environment via connectivity between vehicles and the infrastructure. This study investigates if and how two representative communications approaches—dedicated short-range communication (DSRC) and cellular (3GPP 4G/LTE)—can support various CAV applications. The Virginia connected corridor (VCC), operated by the Virginia Department of Transportation (VDOT) and Virginia Tech Transportation Institute (VTTI), was used as a testbed for this project. To provide a robust evaluation, signal phase and timing (SPaT), data transmitted by DSRC and cellular were collected in the field at various intersections in northern Virginia and compared based on latency and distance coverage.

The latency experienced by SPaT messages over DSRC was below 5 milliseconds (ms), while the latency of cellular network was well below 100 ms. Specifically, the minimum, median, and maximum latency values for DSRC are 0.8, 1.1, and 1.5 ms, respectively; for cellular, they are 7.7, 36.4, and 68.0 ms, respectively. The minimum and maximum communication ranges for DSRC were 430 and 1,365 meters (m), respectively; for cellular, they were 1,171 and 3,751 m, respectively. An application analysis was conducted to assess the impact of latency and coverage on the feasibility of supporting various safety and nonsafety applications, including glidepath, traffic optimization for signalized corridors (TOSCo), transit signal priority (TSP), and red light violation warning (RLVW).

Based on the data analysis, it was inferred that glidepath and TOSCo could benefit from the near-ubiquitous coverage of cellular networks by receiving the data farther away from the intersection, whereas applications like TSP and RLVM, which require a low latency, may not be supported by the cellular network. Finally, opportunities for further study are suggested, which include the study of other performance metrics, such as accuracy and reliability, and the study of alternate communications methods.

• DTFH6116D00030L-693JJ318F000404

• Operations

• FY 2002-2022 / Operations

• Transportation Management

This report presents the findings of the Feasibility Study and Assessment of Communications Approaches for Real-Time Traffic Signal Applications project, sponsored by the Office of Operations Research and Development (R&D), Federal Highway Administration (FHWA), and the U.S. Department of Transportation (USDOT) Intelligent Transportation Systems (ITS) Joint Program Office (JPO). The focus of this project was to investigate if and how two representative communications approaches—dedicated short-range communication (DSRC) and cellular long-term evolution (LTE)—can support differing connectivity-based safety, mobility, and environmental applications that utilize real-time traffic signal data from the infrastructure. To do this, this project assessed the feasibility of supporting several applications based on latency data gathered through DSRC and cellular LTE. Both DSRC and cellular LTE have shown strengths and weaknesses in supporting applications in terms of timing and communication range requirements. It is our intent for these results to help developers and deployers alike improve the safety and performance of the Nation’s roadways.