Autonomous vehicles ‘keep traffic flowing better than drivers’

A fleet of driverless cars working together to keep traffic moving smoothly can improve overall vehicle flow by at least 35 per cent, a study has suggested.

A team of researchers at Cambridge University programmed 16 miniature robotic cars to drive around a two-lane track and observed how the traffic flow changed when one of the cars stopped.

When the cars were not driving co-operatively, any vehicles behind the stopped car had to stop or slow down and wait for a gap in the traffic, as would typically happen on a real road.

A queue quickly formed behind the stopped car and overall traffic flow was slowed.

But when the cars were communicating with each other and driving co-operatively, as soon as one car stopped in the inner lane it sent a signal to all the other vehicles.

Cars in the outer lane that were near to the stopped car slowed down slightly so that vehicles in the inner lane were able to quickly pass the stopped car without having to stop or slow down significantly.

When a human-controlled car was put on the track with the autonomous cars and moved around in an aggressive manner, the other cars were able to give way to avoid the aggressive driver, improving safety.

The results, to be presented at the International Conference on Robotics and Automation in Montreal, will aid research into how autonomous cars can communicate with each other and vehicles controlled by human drivers..

It comes as Stagecoach is testing the UK’s first autonomous buses in Manchester, which are due to start carrying passengers between Fife and Edinburgh via the Forth Road Bridge next year.

Student Michael He, a co-author of the study, said: “Autonomous cars could fix a lot of different problems associated with driving in cities, but there needs to be a way for them to work together.”

Co-author and fellow Cambridge student Nicholas Hyldmar said: “If different automotive manufacturers are developing their own autonomous cars with their own software, those cars all need to communicate with each other effectively.”

Using scale models of commercially-available vehicles with realistic steering systems, the researchers adapted them with motion-capture sensors and a Raspberry Pi, a credit card-sized computer, so the cars could communicate via wi-fi.

They tested the fleet in “egocentric” and “co-operative” driving modes, using both normal and aggressive driving behaviours.

In the normal mode, co-operative driving improved traffic flow by 35 per cent over egocentric driving.