Science

Adding a white traffic light may help driverless cars boost traffic flow

When and if driverless cars become much more common, the green, amber and red traffic lights that we already know may be getting a white sibling
Depositphotos
When and if driverless cars become much more common, the green, amber and red traffic lights that we already know may be getting a white sibling
Depositphotos

In order to optimize traffic flow, many autonomous vehicles communicate both with one another and with municipal traffic control systems. Scientists are now suggesting that an extra white light at controlled intersections could help incorporate human drivers into the mix.

First of all, as long as autonomous vehicles (AVs) remain a rarity, the ol' green/amber/red traffic light system probably works best – no need for an extra color. Assoc. Prof. Ali Hajbabaie and colleagues at North Carolina State University, however, believe that could change as AVs become more common.

That's where the "white phase" comes in.

The idea is that as groups of AVs are approaching an intersection, they will communicate with one another and with the computer running the lights at that intersection. In order to get through the intersection as quickly and efficiently as possible, all of those AVs will coordinate their movements – a certain number of cars going in one direction will wait, while a certain number of cars going in the other direction will pass through.

During this phase of traffic flow, the traffic lights will be changed to white. This will let drivers of non-autonomous cars know that right-of-way is being dictated by AV traffic, and that all they need to do is simply follow the car in front of them – if it stops, they stop, and if it goes through the intersection, so do they.

At that same intersection, when the vast majority of approaching cars are not AVs, the lights will revert to their standard green/amber/red routine – the white light simply won't illuminate.

According to the scientists, computer simulations based on real-world traffic flow show that the idea definitely has some merit. In some cases, for instance, the white phase could reduce traffic delays by over 90%.

"The simulations tell us several things," says Hajbabaie. "First, AVs improve traffic flow, regardless of the presence of the white phase. Second, if there are AVs present, the white phase further improves traffic flow. This also reduces fuel consumption, because there is less stop-and-go traffic. Third, the higher the percentage of traffic at a white phase intersection that is made up of AVs, the faster the traffic moves through the intersection and the better the fuel consumption numbers."

That being said, he adds that even in scenarios where just 10% of the cars at an intersection were autonomous, the white phase still reduced traffic delays by 3% – and the light wouldn't necessarily have to be white, just some agreed-upon fourth color.

A paper on the research was recently published in the journal IEEE Transactions on Intelligent Transportation Systems.

Source: North Carolina State University

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17 comments
Trylon
Great in simulations. Not so great in the real world, where many drivers really don't give a damn about anybody or anything else, including pedestrians, other drivers and autonomous cars. They'll ignore the white light. They'll just think, "Yeah, so what are the robot cars going to do? Crash into me? I'll just go through and they'll yield because they have to."
DavidB
England and it’s former colonies think “yellow” means “rev your engine and get ready to jump,” whereas Americans think “yellow” means “slow down, this light’s about to go red.” Of course, many Americans think “yellow” means “speed up and try to beat the upcoming red light,” resulting in cars rushing through the intersection after other cars have seen green and started into the intersection themselves.

I’ve driven under both sets of rules, and I still can’t decide which makes more sense: “green, yellow, red” or “red, yellow, green.”
RichardNygaard
As a former police officer I don’t think this idea will be anything but a disaster. Basically it’s saying just do whatever the idiot in front of you does. Might work fine in some countries where traffic laws are generally followed and respected by most drivers. The US is not ready for roundabouts, we can’t even keep right.
Chase
"According to the scientists, computer simulations based on real-world traffic flow show that the idea definitely has some merit."

Did those simulations account for just how stupid some of us are? An uncomfortably large amount of the US population cannot even properly navigate a roundabout or a double turn lane, and they want a fourth color?
Badja
I'm sure, whether they add white traffic lights or not, the autonomous car manufacturers will pay fees (bribe) to the traffic authorities to give their vehicles right of way over human driven cars. They will justify this as a safety measure.
frb
i would think autonomous cars can negotiate with each other and the traffic lights without having to add a extra color
Brian M
Do you actually need a third colour? Could just flash one of the other colours to do the same.
christopher
Because white is new color that's never seen anywhere around intersections already...

Not to mention the elephant in the room - no need whatsoever for any of this: if the lights themselves monitored the incoming traffic, they could already decide how to fix the flow right now, for everyone, all the time.
Rakkasan
Traffic lights are antiquated. They need a total smart system for AV. How can you just follow an AV and expect it to make a sound judgment?
Steve Moulden
What about color blindness? Especially at night, I see green lights as white, and the red and yellow are very similar in color. I work traffic lights by the location of the light that is on.