MADRID -- A convoy of self-driving cars took to a public motorway in Spain in normal traffic, a world first, according to Swedish car maker Volvo.

A professional driver took the lead in a truck, and was followed by four self-driven Volvo vehicles: a second truck and three cars, Volvo said in a statement.

Vehicles in the road train were equipped with safety systems including cameras, radar and laser sensors, enabling them to monitor the lead vehicle and other vehicles on the road.

"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 leader," Volvo said.

The cars successfully drove for 124 miles on May 22 along a motorway outside Spain's northeastern city of Barcelona.

Volvo Car Corporation's project manager, Linda Wahlstrom, was filmed driving one of the cars in the convoy as the system instructed her to lift her feet from the pedals and then remove her hands from the wheel.

As the car sped along the highway at 53 mph, she leafed through a magazine.

"It is quite funny to see the passing vehicles. They are quite surprised seeing me not driving the car but reading a magazine," Wahlstrom said.

"The project aims to deliver improved comfort for drivers, who can now spend their time doing other things while driving. They can work on their laptops, read a book or sit back and enjoy a relaxed lunch," Volvo said.