A system of flashing LEDs would see a series of rapid pulses of visible light being used to to relay information from one car to another. These LED flashes will be so short in their intervals, that we would not even be able to notice it in the first place. This allows self-driving cars to “inform” one another about the traffic conditions that is right up ahead, or perhaps an accident that has already happened, making the entire autonomous driving system all the more intelligent this way.
It is said that the required data rate so that such information can be sent from one car to another is low enough for a regular camera to work well with it, and existing cars which use LEDs now can relay such messages already. However, special equipment will need to be retrofitted so that the entire system will be a whole lot more robust.