You know about dialing 911 for emergencies and 411 for directory assistance. Now there's 511.

These three digits soon may become the most-dialed on your cell phone. Why? Because the 511 phone number increasingly links you to detailed traffic and road construction information across the country.

The 511 number already works in Nebraska, Utah, Arizona, Montana, North and South Dakota, Kansas, Iowa, Minnesota and Kentucky, as well as Miami and San Francisco. Virginia drivers can call 511 to find out about problems on Interstate 81. Other states are either preparing their own program or, like South Carolina, studying the idea.

By the end of this year, 14 more areas will be added. By 2005, half the U.S. population will have the 511 service, according to the 511 Deployment Coalition, made up of the American Association of State Highway and Transportation Officials, the Intelligent Transportation Society of America and the American Public Transit Association.

When you call the 511 number, you then have to give voice prompts to receive information. This way, drivers' hands remain on the wheel.

For the latest on the 511 network, contact the Intelligent Transportation Society of America, online at www.itsa.org, or by calling (202) 484-4847.