The computer tells us to continue on Constitution Avenue to reach Capitol Hill. But we hit one of Washington's notorious detours and a cop directs us to turn.

How will the car's navigation system handle an unscripted change of itinerary?

It's a recent Thursday afternoon, and I'm in an Avis rental car for a test of the company's satellite global positioning system, called Avis Assist. Avis is rolling out the navigational service at all U.S. locations for $9.95 a day. The system is essentially a radio receiver that picks up signals from orbiting satellites that identify the car's location and the distance to its destination.

When we turn off Constitution and pull to the side of the road, the system pinpoints our location and updates our directions. We're back on our way.

With the summer travel season expected to be the strongest since 2000, car rental companies are dressing up their vehicles with new forms of technology to attract consumers. The navigational systems go far beyond the days of wrestling with oversize folded maps.

Hertz offers a navigational system called Never Lost for $9 a day. In place since 1997, it also employs GPS. The driver programs in the destination, and the car's screens display maps and directions based on the system's software. The devices also give audio cues. Hertz has the system in 40,000 cars and plans to add 10,000 more by the end of the year, said spokesman Richard Broome. Enterprise doesn't have navigational systems in its cars.

With the Avis service, a customer receives a Motorola phone to call a guidance operator who enters the travel data in the system. At the outset, the company will have 30 to 40 operators available. The phone then mounts on the dashboard with the screen showing a map of the car's movements. Simultaneously, the service provides audio directions. The phone doesn't permit any other calls, and personal cell phones cannot be used with the system.

Our first destination was the Castle at the Smithsonian Institution on the Mall. At the wheel was Avis spokeswoman Susan McGowan. Motorola spokesman Tim Courtney came along to provide commentary on the technology. We left The Washington Post's offices and drove north on 15th Street to Massachusetts Avenue NW, where we turned right, toward Thomas Circle. As we rounded the circle the system directed McGowan to veer to the right, onto 14th Street.

Hearing the automated directions was difficult at times, and turning up the volume distorted the sound somewhat. It is possible, however, to hear the cues again by punching a repeat button.

On the way to the Smithsonian, we were suddenly notified that we were off route, even though we were right on track. Motorola's Courtney explained that bridges, tall buildings and trees can cause momentary lapses in the signal. Once the signal is restored, the directions pick up again as originally requested.

When we reached the Smithsonian, I decided to give the system a more obscure address on Capitol Hill. We called the Avis guidance operator, who answered after five rings and put us on hold. When we did get the chance to tell the operator our plans -- bam, the call was lost. We called back and were given a route to Capitol Hill that was longer than one I knew.

"It may not be the fastest route, but I can trust it will get me there," McGowan said.

She added that having access to a live person for directions and assistance is a comfort to some travelers, especially women traveling alone in unfamiliar cities. On a recent trip to Los Angeles, McGowan said she kept the operator on the line through each driving instruction until she reached her destination.

Navigational systems have won some devotees. One frequent flier, Dan Gallagher of McLean, often rents Hertz cars and is a member of the company's elite-level loyalty program. When he upgrades a rental, he receives a complimentary Never Lost navigational system, which he said he prefers to "dragging a bunch of Mapquest papers with me."

Washington frequent flier Gerald Role said he prefers to print out directions and study them before setting off. That way, he said, he isn't caught off guard by sudden turns or twists in the road.

Memorial Day Planning: If you're flying over the Memorial Day weekend, you should arrive at the airport at least 90 minutes before your departure, airport officials say, especially if you're leaving on Thursday or Friday and returning Monday or Tuesday.

Redskins and Independence Air: The new Dulles-based low-cost, low-fare airline, Independence Air, announced last week that it is the official airline of the Washington Redskins.

No, that doesn't mean that 300-pound linemen will be squeezing in next to you aboard Independence Air's 50-seat regional planes. Rather, Independence Air will be the only airline advertised at FedEx Field during Redskins games for the next three years. Independence Air begins flying June 16.