Features

All GPS navigators on the market today include pre-loaded maps and provide spoken directions and automatic rerouting if you miss a turn. The following are additional features to look for when comparing models, depending on your needs. (These GPS features and other key elements are specified in our GPS model pages, available for each unit included in the Ratings charts.)

Screen size

We've tested portable systems with screens ranging from 2.5 to more than 5 inches. The smallest can be hard to see, and their small touch-screen buttons can make it tedious to enter an address. On the other hand, the largest units can be bulky to carry, and when mounted to the windshield tend to obstruct more of your view of the road. A 3.5-inch screen measured diagonally is a good compromise, but 4.3-inch wide screens are easier to read and use.

Spoken street names

Better systems tell you to turn onto a street, highway, or route number by its name rather than the more general "right turn ahead" or similar generic instruction. This GPS feature, often called text-to-speech, helps you to keep your eyes on the road and less on the GPS unit. It is especially useful in busy, unfamiliar areas where driving is challenging and roads may be close together.

Real-time traffic reports

Units with traffic information can alert you to a problem or slowdown ahead in time to avoid it. Some will even ask if you want to find another route and will detour you at the touch of a button. The real-time data is available to subscribers through a cell-phone network, FM signal, or satellite radio service. But the service is currently available only in some cities and the quality of information--like any traffic reporting--can vary or be less than current. Still, we have found that it can help. Expect to pay a subscription fee, and some devices require an additional receiver costing up to $200. Higher-end GPS models include a built-in receiver. The latest trend is free traffic information, supported by small banner ads that pop up occasionally. Garmin, Magellan, and Nextar all offer this feature on some models. Another emerging trend is that some new models factor in historical traffic data and can route around known congestion patterns such as rush-hour traffic.

Predictive data entry and dynamic search

These GPS features make entering a city name or address faster. With predictive data entry, as you type, the screen's keyboard will highlight only letters that help complete a known name. If you type "Pitt", for example, the system will then highlight "S" as the next letter for Pittsburgh.

Almost all models have dynamic search. This common GPS device feature helps narrow things down as you tap in an address. With dynamic search, if you type "San", the unit might offer up a list of choices including San Diego, San Francisco, Santa Barbara, etc. You can then pick one from the list or just keep typing.

Detour feature

If you see traffic building up ahead, a manual "detour" button will find you an alternative route. Some models allow the user to select a specific distance to route around a problem. Traffic-capable devices integrate their traffic information with detouring functions, prompting a user to choose an alternative route when traffic conditions are unfavorable. That can be helpful in evaluating options before changing course.

Routing option

Some systems can alert you to toll roads on your chosen route and often allow you to select a route that avoids them. Other routing options you might want to look for include multiple trips, or routes for biking or walking that avoid highways and let walkers go against one-way traffic.

Mounts and mounting

Most portable systems mount to the windshield using a large suction cup. Manufacturers have typically used either an angled rigid arm or a flexible gooseneck to attach the unit to the suction cup. We recommend the rigid arm mount because the less-common goosenecks tend to vibrate when the car is in motion.

Something else to look for is a unit that is easy to install and remove from the mount. Typically, a unit slides onto a mount or snaps into it. The power cord either plugs into the mount or directly into the unit. We've found the most convenient to use are mounts that allow you to snap the unit in and release it with the push of a button. If the power cord plugs into the mount, that makes it easier to quickly remove and reinstall the unit.

Minnesota prohibits drivers from mounting any devices to the windshield; California once did but changed that law in January 2009. Check laws in your area before purchasing. An alternative is a "bean bag" mount, which simply sits on the dashboard. Those are a cinch to use, and they stay put pretty well. But beanbags can slide and even fall off the dashboard during abrupt movements. Another mounting method included with most portable GPS devices is a self-adhesive plastic disk that adheres to the dash, giving you a place to attach the suction cup. If you live in Minnesota, or just don't want to have anything hanging from the windshield, make sure you choose a device that includes a disk.

Power Supply

All portable systems can be powered through a car's 12-volt socket, and most have an internal rechargeable battery. An internal power supply helps to minimize a tangle of cords in the car. We found that those units typically operate for 2-4 hours on a charge, although testing revealed significant variance among models. Internal power also allows you to practice using the system and program driving destinations while you are away from the car, or to use the device as a hand-held tool when traveling, walking, or bicycling. An AC power adapter is sometimes included with the systems, allowing the device to be used and recharged indoors. Some can also be charged using a USB cord attached to a computer.

Bluetooth compatibility

This allows you to make and receive telephone calls using the unit's internal speaker, microphone, and screen. Automatically quiets directions while call is being made. Can display user's telephone book, and shows caller ID on-screen. A nice tie-in, this feature allows for dialing point-of-interest locations found in the GPS device. Requires a Bluetooth-compatible telephone.

MP3 player

With a music player, the device can store and play pre-loaded audio files, either through its speaker or through the car stereo using an FM transmitter or a cord from the GPS headphone jack to the car's auxiliary port. This GPS feature means the unit can also be used as a portable music device away from the car. File capacity varies by unit. Most navigation units have SD card expansion slots for file storage.

Video player

Shows videos previously downloaded to unit's hard drive or stored on an SD card. Using this GPS feature normally disables navigation while the video is being shown. This may be appreciated by families on road trips and frequent flyers.

Photo viewer

The viewer allows users to display previously loaded photos or photos stored on an SD card, as a single image or as slide shows.

Foreign languages

Many units offer spoken and displayed directions in Spanish and French in addition to English, and several have even more choices. Some TomTom models can provide spoken directions in more than 30 languages, but can't display them all on the screen. For specific language needs, it is recommended that you check with the device manufacturer for the latest out-of-the-box abilities, and additional language features that might be available by download.

See also:

Car batteries

Car seats

Special Section:
Guide to Driving Green

Winter tires