Self-driving cars know where to move with white traffic lights
North Carolina State University engineers suggest the idea of adding white traffic lights to allow self-driving cars to communicate with each other while cruising on busy roads. The proposal, led by Professor Ali Hajbabaie, is a traffic system that allows these autonomous vehicles to organize their movement through the intersection without stopping too often. In the normal system, traffic lights have three colors: red means stop, green means go, and yellow means prepare to stop. In the new system, there is an additional white light.
This light activates when there are enough autonomous cars near the intersection. When the white light turns on, it signals that self-driving cars are taking control of the traffic flow. Human drivers just have to follow the car in front. If that car moves, they move. If it stops, they stop. When there are not enough autonomous vehicles, the traffic light switches back to the normal red-yellow-green pattern, meaning this system depends on the number of automated cars present at a given time.
image by of Timo Wielink, via Unsplash
Autonomous vehicles stop less with white light
The researchers call this method the mobile control paradigm. Each autonomous vehicle has a built-in computer that can calculate its speed, distance, and position, and together, these vehicles create a network of moving controllers that can organize traffic more efficiently than a fixed traffic light system. In earlier work from 2020, the researchers used a centralized control system, where one main computer at the intersection made all the decisions. The new version is distributed, meaning every self-driving car contributes its own computing power. To test the concept, the engineers used microscopic traffic simulators and compared intersections with and without the white phase to see how traffic, fuel use, and waiting time changed.
The results showed that when self-driving cars were present, traffic always moved better than when all cars were human-driven. When the white phase system was added, there was a noticeable improvement because cars spent less time stopping and starting, which also saved fuel. The researchers note that the color of the white light is not important. It could be any color, as long as it clearly tells drivers to follow the car ahead. Although the concept is still being tested in simulations, the engineers believe it can be adapted gradually and that some parts could be added to existing intersections and self-driving cars without redesigning the entire roads and systems.
image courtesy of North Carolina State University | photo by Siyuan
image by Eliobed Suarez, via Unsplash
image generated on ChatGPT with the prompt asking to add a fourth light colored white on a stoplight
image by Birk Enwald, via Unsplash
project info:
name: White Phase Intersection Control Through Distributed Coordination: A Mobile Controller Paradigm in a Mixed Traffic Stream
team: Ramin Niroumand, Leila Hajibabai, Ali Hajbabaie
institution: North Carolina State University | @ncstate
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