If it depends on the scientists, the traffic light will have an additional color

Red, orange, green and… white! With the extra tan, researchers are already preparing for the seemingly inevitable rise of the self-driving car.

When approaching a busy intersection, you may just come across a traffic light. People all over the world know its colors: red means stop, for example, and green means you can continue. But if it’s up to American researchers, this old and familiar traffic light will soon undergo a slight metamorphosis; they want to add a white light to it. This can be read in the magazine IEEE Transactions on Intelligent Transportation Systems.

Autonomous cars
The rather radical proposal stems from the expectation that the number of self-driving cars will increase dramatically in the coming years. These autonomous cars can communicate with each other, but later probably also with the computer that controls the traffic lights. This mutual communication can greatly improve the flow. For example, a self-driving car that “knows” that its route will intersect the route of another self-driving car in five minutes can slow down a bit, after which it will not meet the other car at the intersection and can continue driving. immediately. In the same way, communication with traffic lights can also ensure that self-driving cars no longer have to stop and speed up at intersections – actions that cost time and fuel (or electricity).

traffic controllers
It sure sounds wonderful. But the practice will be – at least in the early years – a bit more erratic. Indeed, in addition to self-driving cars, there will also be human-driven cars on the road. These cars do not communicate with self-driving cars or traffic lights and, in this sense, threaten to impede the flow of traffic. But researchers have now found a solution.

They propose to use self-driving cars as a kind of traffic controllers and communicate this to human drivers by means of an additional (white) lamp on the traffic lights. “Red lights always mean you have to stop,” says researcher Ali Hajbabaie. “Green lights always mean you can continue. And the white lights tell human drivers to just follow the car in front of them.

How it works?
When self-driving cars approach an intersection, those cars — by communicating with each other and with the computer that controls the traffic lights at the intersection — coordinate with each other to get through the intersection first. As mentioned, the goal is to get the best possible flow of self-driving cars. For example, adjusting the speed of cars approaching the intersection so that they don’t all arrive at the intersection at the same time. Or by mutually agreeing that the longest convoy of self-driving cars can drive to the intersection. By communicating with each other and making deals, smart, self-driving cars know exactly what to do to get through that intersection as efficiently as possible. But “dumb” cars driven by humans don’t have this information. As a result, they are likely to experience more delays at intersections and, in the worst-case scenario, even thwart self-driving cars’ attempts to achieve rapid throughput. The white traffic light can prevent this, say the researchers. The white light comes on as soon as the self-driving cars – approaching the intersection – have mutually coordinated which car is allowed to enter the intersection at what time and have therefore together found a way to ensure smooth traffic flow. The white light then signals non-autonomous cars to do what the (autonomous) car does for them at the intersection. When this car stops, they stop too. And if the car drives, they drive too. In this way, they are somewhat taken in tow by the self-driving cars and they also benefit from the agreements that the smart cars have made between themselves and therefore from a smoothness at the crossroads.

Communication is important
“Giving some traffic control to self-driving cars is a relatively new idea,” Hajbabaie said. “It can be used to control traffic in any scenario involving self-driving cars. But we think it’s important to use such a white light at intersections because it communicates to human drivers what’s going on and they know also what to do when approaching the intersection.

Sometimes back to red, orange and green
For traffic at a busy intersection to be partially controlled by self-driving cars, it is necessary for a considerable number of self-driving cars to approach that intersection. If not, and many human-driven cars are heading towards such an intersection, the white light cannot be used. In this case, the traffic lights will again use the old familiar colors – red, orange and green – to guide traffic safely through the intersection.

The researchers showed by means of simulations that the use of white light was definitely worth considering in the future. “These simulations tell us a number of things,” Hajbabaie said. “First of all, self-driving cars improve traffic flow anyway.” The same is true in the absence of what the researchers call “the white phase,” in which self-driving cars under the white light take over “regular” cars. “Secondly, when self-driving cars are present, the ‘white phase’ further improves throughput. And it also leads to less fuel consumption, because there are fewer stops and starts. Third, the higher the percentage of self-driving cars on an intersection in “white phase”, the faster the traffic passes through the intersection and the better the fuel consumption figures. Very concretely, the delay seems to decrease by approximately 3% when 10% of the cars at an intersection with white lights are autonomous. But if self-driving cars account for 30% of cars at an intersection with white traffic lights, delays could already be reduced by 10.7%.

The researchers recognize that self-driving cars aren’t quite ready for the white-phase intersections they deliver. And governments are probably not keen on replacing or extending all traffic lights with white light. But that could of course change in the future. Alternatively, future policy makers can always consider the use of white traffic lights for specific locations – such as certain busy intersections where traffic tends to accumulate.