When Starry Rhoads and her husband John followed their navigation system's directions to take a road through Oregon's picture-perfect winter wilderness, they never once thought that their lives would be in danger. Marked as a through road by the aftermarket GPS device in their Toyota 4x4, it would eventually peter out to become little more than a rutted country pathway. But by this time, one of Oregon's famous snap snowstorms had blocked the road behind them.

"We got stuck for three days," said Starry Rhoads, describing the harrowing incident that occurred late last year.

??Rhoads said the couple, from Reno, Nev., had checked their route on maps beforehand and knew which way they wanted to go, but "the device had a mind of its own. There was no indication this should not have been a road we were on, there were cars on it, and signs, but after 20 miles there was no road.

??"At the time we turned onto the road it was sunny and clear and a beautiful day. But then it snowed a little. Next night it snowed a lot. The next night we didn't know an even bigger snow was coming, and if rescuers hasn't reached us that night, they told us we wouldn't have been picked up till spring."

Only As Good As The Map

Most new cars these days have at least the option of a factory-installed navigation system and aftermarket units hanging from windshields have become a common sight. Many drivers consider navigation systems essential to their daily lives. Garmin, the market leader for aftermarket units, forecasts sales of more than $3 billion for 2010.

Yet the Rhoad's experience will not be surprising to thousands of motorists who have been led astray by their navigation systems -- though usually it's more of a mild annoyance than a life-threatening mistake.

?Environmental factors often play a large part when these devices act up: Tall buildings, for example, can interfere with the signal relayed to the device from a satellite overhead, and result in jumbled coordinates and confusing directions. Like in the Rhoads case, weather can play havoc on rural roads than are prone to flooding or being blocked by snow during a heavy storm. If you live or commute through a growing community, new streets and neighborhoods that are rapidly evolving can also throw your GPS system for a loop.

"[With] obstacles in a large city, big buildings or long overpasses, those signals can bounce around -- for example it's been showing a straight line and suddenly it tells you to take a quick turn," said Jake Jacobson, a spokesman for Garmin.

He said the company issues new maps for its devices every three months, seeking to minimize the effect of new construction on its route maps. Users can sign up for new maps every quarter or for a lifetime of map updates at a reduced price.

?"A lot of it is common sense. It always helps to have looked at your route before you go and have a sense of your journey. I've heard of people who follow it [GPS instructions] blindly despite posted signs and the rules of the road. You don't want to drive through a police barricade," said Jacobson.

Google Maps and AOL's newly re-launched Mapquest service provide online route-planning services that can be printed out and examined before any trip. Garmin also offers its own free route-planning software called BaseCamp.

For some, however, nothing beats a paper map like you'd find at a bookstore or filling station. Rhoads pointed out that her GPS device only viewed short distances at a time, rather than, say, a full 1,200-mile overview of their trip, like you might plot with a traditional road atlas.

What You Can Do

Rhoads says that people should tell their friends or family when to expect them to arrive or come back from their trip, so if they are missed it can speed any alert of emergency services. She says thankfully they were prepared for their long drive with warm clothes, blankets, and food and water. "Without them we wouldn't have survived the snow-drift."?

Drivers in rural areas should routinely pack chains, shovels and blankets and extra food, water, high-energy food, extra clothing, and cell phones – though keep in mind that the more remote the location, the less likely you are to get a signal. Always let somebody know your itinerary.

??Even for general motoring, the emergency safety kit in your car should contain jumper cables, engine oil, de-icer fluid, a flashlight, emergency flares, a distress flag, a first aid kit, a pocket knife, water and snacks, blankets , gloves, scarf, hat, cell phone, ice scraper, shovel, tow chain or rope and a jack.?

Use Your Head

?Even after her experience, Rhoads says their navigation system has "served them well" in numerous trips in rural and metropolitan areas.

The Rhoads caught a lucky break when on their last night in the snow they picked up a weak cell phone network signal, allowing them to send their co-ordinates to the local police force, who forwarded it to rescue dispatchers.

"We should have listened to ourselves rather than the GPS. It seemed like a shortcut but it wasn't. Like anything else you have to rely on your own intelligence, you can't put blind faith in your GPS system. In the future I'll rely more on written maps or I'll stop and ask," she said.

"Human judgment is still the best tool," confirmed Garmin's Jacobson. "Our devices are a great source to help get from point A to point B whether cross country or daily commute, but we don't want to give the impression we want to turn their brains off when they turn their Garmins on."