Car-to-car communication have a bigger impact than the advanced vehicle automation technologies that have been more widely heralded. Though self-driving cars could eventually improve safety, they remain imperfect and unproven, with sensors and software too easily bamboozled by poor weather, unexpected obstacles or circumstances, or complex city driving. Simply networking cars together wirelessly is likely to have a far bigger and more immediate effect on road safety. The technology that warned of the impending collision will start appearing in cars in just a couple of years.

Creating a C2C network is still a complex challenge. The computers aboard each car process readings being broadcast by other vehicles 10 times per second, each time calculating the chance of an impending collision. Transmitters make use of a new wireless standard, 802.11p, to authenticate each message.

Also called vehicle-to-vehicle (V2V) communication, it lets cars broadcast their position, speed, steering-wheel position, brake status, and other data to other vehicles within a few hundred meters. The other cars can use such information to build a detailed picture of what’s unfolding around them, revealing trouble that even the most careful and alert driver, or the best sensor system, would miss or fail to anticipate.