A side-by-side comparison of connected vehicle technology at 85 traffic
signals in the Tuscaloosa, AL area showed that latency in delivering
safety messages from roadside units (RSUs) to vehicles via dedicated
short range radios (DSRC) and LTE cellular (C-V2N) was “approximately
equivalent,” according to a study
by the University of Alabama which was presented at the ITS America
Annual Meeting in Washington, D.C.
The research, conducted by Alex Hainen, Ph.D., Assistant Professor at
the Department of Civil, Construction and Environmental Engineering at
The University of Alabama, looked at installation, maintenance, latency
of transmissions from RSUs and scalability for in-vehicle deployment.
The research was conducted in conjunction with the Alabama Department of
“As connected vehicle communication methodologies, such as DSRC or
cellular, continue to be debated, we wanted to look at the practical
aspects of these technologies such as which can be quickly deployed by
roadway operators and quickly adopted by the motoring public, and what
role latency played in delivering RSU safety messages,” said Dr. Hainen.
“We continue to look at additional applications for vehicle to
infrastructure communications and how they can play a role in improving
safety and efficiency.”
“We are pleased to support the University of Alabama and Dr. Hainen in
this important work, which is significant and will help to drive
connected vehicle technology to widespread deployment where it will do
the most good,” said Bryan Mulligan, president of Applied Information.
According to the study: “The main justification for choosing DSRC
technology over cellular is that DSRC communications have much lower
latency than cellular communications. However, this project showed the
4G LTE communications had a latency period of less than 300
milliseconds. While this period is longer than the DSRC communications,
this time difference in latency periods have very little difference in
the applications tested with this platform. In the future, higher levels
of automated driving may require low-latency V2V communication, but this
current technology has already shown much potential as a connected
traveler platform that can be easily used by today’s technology.”
The study also concluded that
Cellular technology was much easier to configure and install than the
In terms of configuration, the cellular units have the ability to have
their firmware updated via “Over-the-air” updates.
The most reliable way to update the DSRC units is through direct
ethernet connection and one must be physically at the pole to update
Aftermarket OBUs cost upwards of $1,000 and usually require
modification of the vehicle. This makes distribution of DSRC
technology beyond pilot programs expensive and impractical.
Equipment and Methods
The cellular equipment used was an AI-500-085 Processor unit provided by Applied
Information. The units were installed in the traffic signal cabinets
to monitor and communicate with both the cellular OBU and the
TravelSafely smartphone app. The 500-085 processor also served as the
Signal Phase and Timing (SPaT) translator from the traffic signal
controller to the DSRC radio. DSRC radios were the ConnexUS
Locomate Roadstar. Siemens
M60 advanced traffic controllers were used. The TravelSafely system
worked through both cellular and DSRC radio communication and processed
whichever packet (either DSRC or cellular) arrived first.
About the University
The University of Alabama, the state’s oldest and largest public
institution of higher education, is a student-centered research
university that draws the best and brightest to an academic community
committed to providing a premier undergraduate and graduate education.
UA is dedicated to achieving excellence in scholarship, collaboration
and intellectual engagement; providing public outreach and service to
the state of Alabama and the nation; and nurturing a campus environment
that fosters collegiality, respect and inclusivity.
The full paper can be downloaded from https://itswc.confex.com/data/abstract/itswc/2019/Paper_16664_abstract_2718_0.pdf