Global Positioning System (GPS) receivers that help drivers navigate unfamiliar roads are already familiar features on high-end cars. And the newest GPS technologies, recently tested in Sweden, tell drivers not just where they are, but even how fast they should be driving.

In tests conducted by the Swedish National Road Administration, researchers added customized receivers and warning systems to almost 1,000 cars. The digital-map databases built into the receivers included speed limit information for roads in several cities. In some of the cars, a black box on the dashboard flashed a light and emitted a warning noise whenever the driver exceeded the local limit. In others, the box displayed the speed limits in addition to the warning signal; and in a third group, the box was linked electronically to the gas pedal and imposed resistance whenever the driver was speeding. Drivers slowed down, and two-thirds of them reported they would like to keep the warning systems in their cars. Some test drivers did complain, however, that the technology led to “less joy in driving” and a “feeling of being controlled.”

Despite these discomforts, the Swedish government hopes to make warning systems mandatory for all cars by 2015. Charles Thorpe, director of the Robotics Institute at Carnegie Mellon University in Pittsburgh, calls the Swedish trial “an important step” toward vehicle systems that will use location information to keep passengers and pedestrians safe. Indeed, the Swedish researchers are now busy adding the coordinates of street signs and traffic lights to the national road database. As a result, GPS-based technologies will have the ability within a decade to warn drivers when to stop, says Torbjrn Biding, head of the administration’s traffic management division.

Some major car manufacturers are following Sweden’s lead. Christopher Wilson, group manager for telematics and safety research at DaimlerChrysler, expects that by 2012, the company’s vehicles will be equipped to deactivate cruise control automatically whenever they enter school zones or turn onto highway exit ramps. By 2022, Wilson adds, cars with GPS receivers and short-range wireless transceivers should be able to tell one another where they are, helping drivers avoid collisions and determine who has the right of way at an intersection. Might robotic cars be the ultimate solution to road rage?