A self-driving car makes choices based on algorithms. As a result, the movements an autonomous vehicle makes can be unexpected for human drivers, who sometimes judge situations differently from a computer. A new system could help and make the movements of self-driving vehicles more visible to road users and pedestrians.
The system in question is Mitsubishi Electric's Safe and Secure Lighting system. This system alerts road users and pedestrians of the movements a vehicle or its passengers are about to make. To do so, the Safe and Secure Lighting system uses signals projected on the road and on built-in screens inside the car. Mitsubishi claims that the system can not only make the actions of a self-driving vehicle clearer, but also those of human drivers.
Projecting arrows on the road
For example, if a vehicle starts reversing, the system can warn fellow road users or pedestrians by projecting arrows on the road behind the vehicle. In addition, the system can use projections to warn if passengers want to get out and start opening the vehicle's doors.
Mitsubishi claims that the system automatically activates based on the actions of the driver or the vehicle itself. The system thereby gives both bystanders and drivers of other vehicles enough time to react and anticipate the vehicle's movements.
Experiment by Ford
Mitsubishi, by the way, is not the only company working on such a warning system. Ford is also experimenting with it. The carmaker points out that human drivers in cars use, among other things, hand signals to communicate their intentions to other road users and pedestrians. However, an autonomous vehicle does not have a human driver and therefore cannot use such signals.
Ford announced in September that it had collaborated with the Virginia Tech Transportation Institute to research a method of communicating the intentions of self-driving vehicles in a different way. This research shows that light signals are the most effective method to develop a 'visual communication protocol' for autonomous vehicles.
Light bar on windscreen
The company has also experimented with this in practice. Ford fitted a Transit Connect with a light bar, which was mounted on the front of the bus. To simulate an autonomous vehicle without actually using an autonomous vehicle, the driver of the vehicle was given a special suit in the same colours as the seat coverings. This made the driver invisible to other road users and pedestrians.
Ford tested three signals during the experiment:
- Vehicle stops - two white lights moving inwards from the outer sides of the light bar indicate that the vehicle is going to stop and come to a complete stop.
- Vehicle drives autonomously - four white lights in the middle of the light bar warn that the vehicle is driving autonomously.
- Vehicle is going to drive - four rapidly flashing lights in the middle of the light bar indicate that the vehicle is going to drive.
Tested on public roads
The system was experimented with on public roads in the US state of Virginia in August, covering about 2,900 kilometres with the modified Transit Connect. During the experiment, more than 150 hours of data were collected and over 1,650 signals were given using the light bar. The reactions of other road users and pedestrians were recorded using several cameras mounted on the vehicle.
Unfortunately, the results of this experiment have not been published. However, Ford does say that the data helps to better understand how other road users adjust their behaviour in response to autonomous vehicles and the signals they send. Ford is working with the International Organisation for Standardisation and SAE International, among others, to create a standard for such a visual communication protocol for autonomous vehicles.
Author: Wouter Hoeffnagel
Source: Mitsubishi Electric
Source: Ford (pictured)
