Volvo has been making progress with its driver assistance system for more than a year. Recently, the carmaker's Safe Road Trains for the Environment program reached a key milestone.

With a specially equipped caravan in place, researchers sent the fully functioning "road train" into testing, during which drivers enjoyed their rides without ever needing to touch the steering wheel or other controls.

The technology utilizes cameras and radar-based sensors, and the vehicles in the caravan can travel up to 55 miles per hour while maintaining 20-foot separation. By the end of 2012, the SARTRE team intends to add up to six vehicles in the line. When might it enter the marketplace? It's still a ways a way, but if and when it does, it could improve fuel economy, reduce congestion and diminish driver error.