Self-driving cars, should they ever become a reality, won’t only make it much easier to navigate around a new place, they should make long journeys much more comfortable, too.

Safe Road Trains for the Environment (SARTRE), funded by the European Commission, is a project that’s been researching ways to automate long-distance driving since 2009.

The idea is that one or more automatic ‘slave’ vehicles follow a lead vehicle, which is under manual control, to create a ‘road train’. The vehicles automatically maintain a safe distance from each other and travel at the same speed, which should reduce the traffic ‘accordion’ effect that causes motorway congestion.

Since the slave cars are driven automatically, the drivers are also free to occupy themselves in more interesting ways on the journey, such as watching a film or getting on with some work — although they still sit behind the wheel.

SARTRE recently demonstrated a road train across 125-miles of Spanish motorway. Three cars and one lorry, all made by Volvo, travelled at 52mph with a 6-metre gap between each vehicle.

The cars were fitted with an array of sensors that allowed each one to monitor the vehicle in front and the ones around them (the demonstration took place on a public road), and information about when to brake and when to accelerate was transmitted wirelessly.

Linda Wahlstroem, project manager for the Sartre project at Volvo Car Corporation, told BBC News:

“Driving among other road-users is a great milestone in our project. It was truly thrilling. People think that autonomous driving is science fiction, but the fact is that the technology is already here. From the purely conceptual viewpoint, it works fine and road train will be around in one form or another in the future.”