Using light signals for safe communication in future road transport

LED strip gives automated vehicles 'a voice'

Light is a good way of transmitting simple messages to other road users. Language and symbols, in contrast, can easily lead to misunderstandings. The project partners have developed a special LED light strip with this in mind. It runs beneath the windows and around the whole car, flashing several times if the automated vehicle wants to let a pedestrian cross the street. The message is "I am stopping for you."

"We have devised a completely new language in order for this kind of communication to work. We tested and verified everything meticulously beforehand – from the colours to the duration of the flash and the number of repetitions," says DLR scientist Anna Schieben, who was in charge of the project. A second small lamp attached to the front of the windscreen at rear-view mirror level supplements the light strip. It can only be seen by a single person, who therefore knows that the flash emitted by the LED light strip is meant for them. The vehicle tells the rod user, "I am signalling to you", thus preventing any misunderstandings.

Support – communicating about movements and driving style

"That said, light signals alone are not sufficient for communicating in traffic," stresses Schieben. "The automated vehicle also has to be clearly seen to adapt its driving style, for instance by slowing down to a significant extent. Only then will people be confident that the car has actually noticed them." The interACT team developed a central software module for that purpose. This adjusts the driving style of the automated car at the same time that the light signals are displayed.

Seen through a scientific lens – human–machine communication

At the beginning of the project, the researchers used cameras, radar sensors and surveys to investigate how communication generally works in road traffic. From this they derived requirements for automated vehicles and used simulations, volunteer studies and real scenario tests to develop two demonstration vehicles, including all of the necessary hardware and software components. The team primarily looked at relatively uncontrolled situations in their scenarios, such as crossings without traffic lights or car parks. In such places, road users are forced to communicate and cooperate with one another. When does the light need to come on? How close can and must the vehicle be when that happens? How easy is it to see the light? In subsequent studies with test subjects, they also learned how people reacted to communicating with the automated vehicle and determined which misunderstandings might arise, for example due to the presence of non-automated vehicles in the vicinity.

Project partners and funding