Connectivity to real-time traffic signal data is a key component of Connected Vehicle (CV) applications. This field study analyzed the latency differences (analogous to delay) between two communications approaches—DSRC and cellular 4G/long-term evolution (LTE). The Virginia Connected Corridor (VCC), a cluster of more than 60 intersections in northern Virginia equipped with roadside units (RSUs) served as the testbed for this study. Results from the study were used to assess the feasibility of these communications approaches in supporting different types of connected and automated vehicle (CAV) applications that use signal phasing and timing (SPaT) data from infrastructure systems.
SPaT data was collected at three separate intersections within the VCC, including a 4-way intersection in dense area, a T-type intersection near a small shopping center, a major arterial, and a nearby interstate corridor in a suburban area over rolling hills. Two data delivery paths were explored:
- Cellular (SPaT messages broadcasted from RSU to be received on a laptop via a VCC cloud-based system; and
- DSRC (SPaT messages broadcasted from RSU to be received on the OBU).
Data collection occurred over the course of one day at each site and was broken up into separate morning and afternoon sessions, wherever possible, to cover different levels of traffic demand. Data was collected over runs of 60 to 90 minutes.
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