Can my car tell me the speed limit?

While the 21st century hasn't yet delivered on all the science-fiction promises of yesteryear, it has managed to make our driving experience a little more Knight Rider-esque. Global positioning system (GPS) technology tracks our location, vehicles can park themselves and, yes, with the right equipment, you can look down at your dashboard and find out exactly what the speed limit is. Yet tragically, flamethrowers and ejection seats are still not standard issue on most automobiles.

With a GPS receiver and a relatively clear sky, a driver can pinpoint exactly where he or she is on the globe. This is because a GPS gadget receives signals from at least four of 24 orbiting satellites [source: Global Positioning System] The device calculates its distance from these satellites to determine its exact location on Earth. Sync this up with a computerized map, and you suddenly don't have to mess with cumbersome and confusing road atlases anymore. Most service providers keep these maps reasonably up to date with current road, city and location names, although that shouldn't prevent you from downloading updates frequently.

Some GPS applications allow users to program custom speed warnings. These devices are quickly becoming obsolete, however, as many GPS gadgets go the extra mile and actually tell you what the speed limit is on a given road. Sometimes the data are presented next to your current vehicle speed as well, since GPS can determine this, too. Still, the technology is far from perfect. While such a system might prove highly dependable when it comes to major highway speed limits, less-traveled rural roads might throw it for a curve.

For the paranoid speed demons out there, this technology may seem a little scary. As the technology improves and becomes standard, the vehicles of the future will inevitably know how fast they should be going at any given moment. How long until lawmakers connect the dots and create vehicles that can't be driven over the speed limit? Maybe sooner than you think.

In Japan, the new Nissan GT-R already comes equipped with a speed limiter or intelligent speed adaption (ISA) system. Unless you drive the vehicle onto the GPS coordinates for a racetrack, the onboard computer will prevent the vehicle from going faster than 112 mph (180 kph). The feature prevents drivers from reaching insane speeds and limits them to merely life-threatening velocities, but what happens when ISA systems are less lenient? Politicians and safe driving advocates in the United Kingdom continue to push for mandatory ISA systems in vehicles. They insist that the measure would cut down on accidents, congestion and pollution. In 2003 and 2004, researchers at Leeds University carried out experiments involving 20 ISA-enabled vehicles with largely positive results. Critics, however, argue that ISAs would merely create more problems by turning drivers into unobservant zombies.

Will such technological innovations eventually lead to automated highways full of robotic drivers? Many futurists and transportation experts think so. For the time being, however, no machine overlords can force Sammy Hagar to drive 55. But if he wants to, he can buy a GPS gadget to tell him when he should.

Explore the links on the next page to learn more about vehicle accessories.