Page 9 - May-June 2023 Vol 41 No 1

being driven by a person) simply would researchers compared intersections with, that experience high truck/heavy vehicle
be required to follow the vehicle in front and without, the white phase, as well as activities could be some of the early
of them: if the car in front of them stops, how the behavior is influenced by the adopters for two reasons: the trucking
they stop; if the car in front of them goes sheer number of AVs involved. industry is expected to adopt automation
through the intersection, they go through Hajbabaie said the simulations revealed technology earlier than other sectors,
the intersection. that AVs can improve traffic flow, and truck drivers are professional drivers
Hajbabaie said when too many vehicles regardless of the presence of the white and could adjust to new changes faster,”
approaching an intersection are being phase. For example, if there are AVs he said.
controlled by human drivers (and not present, the white phase improves traffic “Setting up an intersection for this
AVs), the traffic light would revert to the flow. This also reduces fuel consumption, purpose, especially if we use a new
conventional green-yellow-red signal due to less stop-and-go traffic. He said if a indication instead of a new color, is not
pattern. large percentage of traffic at a white phase time-consuming. Training the drivers to
The Mobile Control Paradigm intersection are AVs, the traffic moves react to the new indication and having
“Granting some of the traffic flow through the intersection faster. enough autonomous trucks in the traffic
In the simulation, even when only
control to the AVs is a relatively 10-30% of the traffic at a white phase stream will take time,” Hajbabaie said.
new idea, called the mobile control intersection was made up of AVs, there Pilot Studies Could Take Place in
paradigm,” Hajbabaie said. “It can were relatively small improvements in Selected Ports
be used to coordinate traffic in any traffic flow. But as the percentage of AVs The North Carolina State research
scenario involving AVs. But we think it is at white phase intersections increased, so team has not yet reached out to any
important to incorporate the white light did the benefits. ports, he said, “but commercial vehicles
concept at intersections because it tells “That said, even if only 10% of the seem to have higher rates of autonomous
human drivers what’s going on, so that vehicles at a white phase intersection are vehicle adoption, so there could be an
they know what they are supposed to do autonomous, you still see fewer delays,” opportunity to implement a pilot project
as they approach the intersection.” Hajbabaie said. “For example, when in that setting that could benefit port
He added that the “color” of the ‘white traffic and commercial transportation.”
light’ doesn’t matter. “What’s important 10% of vehicles are autonomous, you Additional considerations for the
see delays reduced by 3%. When 30%
is that there be a signal that is clearly of vehicles are autonomous, delays are team include extending “the white phase
identifiable by drivers.” reduced by 10.7%.” approach to consider pedestrians in
In 2020, the researchers first introduced intersections and provide appropriate
a “white phase” traffic intersection Many Current Traffic Lights Simply Could phasing for them,” he said.
concept, but at that time, the concept Be Reprogrammed “Our next steps will be to include
relied on a centralized computing The researchers acknowledge that other users, such as bikes. We will also be
approach, with the computer controlling AVs are not ready to adopt the new conducting tests in driving simulators to
the traffic light being responsible for distributed computing approach see how drivers react to different traffic
receiving input from all approaching tomorrow, just as governments are not light colors and indications and how they
AVs, making the necessary calculations, going to install brand new traffic lights will follow their front vehicle,” he said.
and then telling the AVs how they should at every intersection in the immediate “We are testing the approach in our
proceed through the intersection. future. small-scale automated vehicle testbed
In this new research solution, the Researcher Leila Hajibabai said the and will follow them with our full-scale
white phase concept relies on distributed adoption phase “will be lengthy; however, autonomous vehicle tests,” Hajbabaie said.
computing, “which is effectively using we are not necessarily suggesting a new The paper, “White Phase Intersection
the computing resources of all the AVs to traffic light. We used the white phase Control Through Distributed
dictate traffic flow,” Hajbabaie said. “This term for simplicity. A new indication Coordination: A Mobile Controller
is both more efficient, and less likely to such as a flashing yellow and red together Paradigm in a Mixed Traffic Stream,”
fall prey to communication failures. For could be used as well. If a new indication is published in IEEE Transactions on
example, if there’s an interruption or time is to be used, the cost and time would be Intelligent Transportation Systems. First
lag in communication with the traffic much less as we do not need to retrofit all author of the paper is Ramin Niroumand,
light, the distributed computing approach signals. Instead, we need to reprogram a Ph.D. student at NC State. The paper
would still be able to handle traffic flow them.” is co-authored by Leila Hajibabai, an
smoothly.” Additionally, the white phase concept assistant professor in NC State’s Edward
Microscopic Traffic Simulators Used could be adopted with only minor P. Fitts Department of Industrial and
To test the performance of the modifications to both intersections and Systems Engineering.
distributed computing white phase existing AVs, Hajbabaie said. “We also NOTE: Many thanks to Matt
concept, the researchers made use of think there are opportunities to test Shipman, Research Communications
microscopic traffic simulators. These drive this approach at specific locations, Lead, University Communications, NC
simulators are complex computational such as ports, which see high volumes State University, for introducing TPW
models designed to replicate real-world of commercial vehicle traffic, for which Magazine to Hajbabaie and his team, and
traffic, down to the behavior of individual traffic flow is particularly important.” for producing an initial overview of the
vehicles. Using these simulators, the “We believe that areas such as ports research.

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