Updated

Companies and researchers have been promising us self-driving vehicles for years. But it wasn't until relatively recently that the technology needed for autonomous cars and trucks even existed. Today, automakers and even Google have proven that autonomous vehicles are almost here. And now Swedish car-maker Volvo has announced a major milestone in the field of autonomous vehicles with its recent demonstration of an autonomous road train traveling across Spain on open public roads.

[Best Tech Awards: New York International Auto Show 2012]

The SARTE road train--a combined effort of Volvo, Ricardo, Applus+ Idiada, Tecnalia Research and Innovation, Institute für Kraftfahrzeuge Aachen and SP Technical Research Institute--saw three Volvo passenger vehicles and a large truck follow and mimic the movements of a manned lead truck on public roadways at speeds of up to 50 mph.

In a video of the test provided by Ricardo, passengers in the autonomous vehicles can be seen releasing their cars' steering wheels and taking their feet of the accelerators as their vehicles transition into autonomous driving mode. Watch as the drivers read magazines and play with their iPads as the cars drive themselves across the Spanish countryside.

According to Ricardo, the autonomous vehicles monitor the lead vehicle using built-in cameras, radar and laser sensors, which are already available on existing Volvo vehicles. Wireless communication between the vehicles allows them to talk to each other, giving them the ability to properly distance themselves from each other.

"People think that autonomous driving is science fiction, but the fact is that the technology is already here," said Linda Wahlström, project manager for the SARTRE project at Volvo Car Corporation. "We’ve focused really hard on changing as little as possible in existing systems.

"Everything should function without any infrastructure changes to the roads or expensive additional components in the cars. Apart from the software developed as part of the project, it is really only the wireless network installed between the cars that set them apart from other cars available in showrooms today.”