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There May Soon Be a Fourth Traffic Light Colour

New research indicates that adding a white light will speed up traffic and improve safety for both cars and pedestrians.

Traffic lights on a city road at night

It's been red, amber, green since the 1920s and is even codified by an international treaty to make sure accidents don't occur because a London driver doesn't understand signals in Tokyo.

Today, systems are in place that control lights for whole cities and digital models of traffic flow have been refined to a fine art (even though it doesn't always feel like that). However, the emergence of autonomous vehicles (AVs) has introduced a new ingredient to traffic management. In addition to being able to drive themselves, they can also communicate with one another as well as central traffic computer systems.

This means that AVs could become part of the traffic control system itself and, according to a new study, work together to improve traffic flow by a considerable margin. Researchers from North Carolina State University suggest that once a critical number of AVs are on the road, a fourth, white traffic signal light can be added to the traditional trio.

The proposition is that when enough AVs are present, the signal turns to white, telling the human drivers to follow the AV or the other car ahead of them. The more AVs, the faster the flow. The team found that even taking pedestrians into account, the general flow still improved for both vehicles and pedestrians by over 25 percent.

Of course, there's still a long way to go before such a system becomes practical and demonstrably safe. But it could become a reality in the not too distant future.


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