Three driverless Volvo cars — a Volvo XC60, a Volvo V60 and a Volvo S60 — were led in a road train following a heavy-duty truck piloted by a professional driver on a public highway among other road users in Spain in what was believed to be a first-time event.

Building on Volvo Car Corp.’s and Volvo Technology's already existing safety systems – including features such as cameras, radar and laser sensors – the vehicles in the road train monitor the lead vehicle and also other vehicles in their immediate vicinity. By adding in wireless communication, the vehicles in the platoon “mimic” the lead vehicle using Ricardo autonomous control – accelerating, braking and turning in exactly the same way as the lead truck.

The autonomous road train is the result of the Sartre (Safe Road Trains for the Environment) project, funded by the European Commission, aiming to develop strategies and technologies to allow vehicle platoons to operate on normal public highways with significant environmental, safety and comfort benefits. Sartre is led by Ricardo UK Ltd and is a collaboration between the following companies: Idiada and Robotiker-Tecnalia of Spain, Institut for Kraftfahrwesen Aachen (IKA) of Germany, SP Technical Research Institute of Sweden, Volvo Car Corporation and Volvo Technology of Sweden. The Sartre project has been under way since 2009.

The project aims to deliver improved comfort for drivers, who could spend their time doing other things while driving such as work on their laptops, read a book or sit back and enjoy a relaxed lunch.

“This is a very significant milestone in the development of safe road train technology,” Tom Robinson, of Ricardo and Sartre project director, said in a press release. “For the very first time we have been able to demonstrate a convoy of autonomously driven vehicles following a lead vehicle with its professional driver, in a mixed traffic environment on a European motorway.”

“We covered 200 kilometers in one day and the test turned out well. We’re really delighted,” said Linda Wahlström, project manager. “People think that autonomous driving is science fiction, but the fact is that the technology is already here.”

A driver rode in each vehicle. In all, the Sartre project has covered more than 6,200 mi. since it began in 2009. The next step for the project is to study fuel consumption with computers controlling vehicle inputs.

While autonomous cars and V2V communication are not new (Google has developed a fully autonomous Toyota Prius), Volvo said this is the first successful attempt of both technologies on a public roadway through traffic. Nevada has already passed laws regulating autonomous vehicles (such as having a licensed driver behind the wheel who can take over control in an emergency) while California has passed laws to define what an autonomous car is.