The car begins to speed up - 20, 30, 40 miles per hour - until suddenly it reaches a sharp corner.
The driver has his hands in his pockets. He keeps them there.
No problem. The seemingly mundane Buick LeSabre sedan takes the turn all by itself.
This is a rolling experiment, an almost fully automated vehicle capable of driving itself with little human intervention.
But the car is only half the wonder. The highway itself sits in the driver's seat, part of a program in southern California designed to find answers to the traffic congestion that snarls most urban centers.
California's Advanced Transit and Highways project will operate the world's first fully automated highway, 7.6 miles of Interstate 15 just north of San Diego.
The system is ready
When it goes into operation in August, motorists driving specially equipped prototypes - like this Buick demonstrated in Berkeley, Calif. - will enter the freeway's express lanes, throw a couple of switches, and relax.
A computer takes charge, steering the car, applying both the brakes and the accelerator.
The test is part of a broader program, the National Automated Highway System Consortium (NAHSC). The seven-year, $250 million public/private partnership aims to prove the validity - and safety - of "smart car" technology.
Is the public ready?
Eventually, proponents say, we'll see automated highways all over America and perhaps the world.
"Eventually," of course, being the key word.
"The pieces will have to emerge one by one and be embraced by the public before we see a fully automated system," cautions Theresa Quinlan, the project's demonstration manager.
But she predicts that motorists will come to accept the idea, much as passengers expect airliners to fly on autopilot.
The goal, however, is not to allow drivers some nap time or to use both hands to handle a burger on the run.
The goal: untangling traffic.
An automated highway means more cars can travel safely in a smaller amount space.
The system, in theory, will space cars as little as 10 feet apart, perhaps tripling the capacity of the roadway.
Sensors under the bumper will read magnetic plugs embedded in the road, which allow the car to stay in the lane and follow the contours of the road.
And an on-board radar will monitor adjacent vehicles and maintain a set, safe distance.
If there's a problem, the car will slow down, return to manual control, or pull off, safely, onto an emergency escape lane.
Proponents concede the experience could prove a daunting at first. It's likely to take some time for people to accept the idea of hands-off driving, especially with car just three feet away, both traveling in excess of 100 m.p.h.
"This is not a system looking for a purpose," says Ms. Quinlan. "It is a system based on need. It has tremendous potential for improving safety and reducing traffic congestion."
It's also, potentially, cheaper. Much cheaper.
Cheaper than concrete
As increasing numbers of cars merge onto the nation's highways, the nation must build increasing miles of highway. That costs millions of dollars per mile.
The trail auto-pilot system costs $10,000 a mile - most of it to outfit the lanes with magnetic plugs every four feet.
The on-board computer system, in current form, would more than double a car's cost (and fill the trunk with electronics). The program aims to pull the cost under $1,000.
Another goal is to test and compare different automation technologies. The approach used on I-15 presents some notable limitations, for example. Once you leave pavement outfitted with magnetic plugs, the automated experience is over.
One alternative: robotic vision. The concept was demonstrated in 1995, when Navlab V, designed at Pittsburgh's Carnegie-Mellon University, became the first car to drive itself coast-to-coast automatically.
Controlling The Cruise
Fully automated roadways are expected to become commonplace sometime after 2020.
But pieces of the technology are already coming into use:
* On-board navigation systems find frequent use in Japan.
And northwest of Chicago, such systems can alert motorists to traffic jams and advise them, via dash-mounted video maps, where to detour.
* Greyhound buses have radar-based collision avoidance systems.
* Within a year, several luxury cars will have "smart" cruise control. They'll use radar, infrared, or laser sensors to maintain safe spacing, even if the car ahead changes speed.
* In a decade, many cars may come with automatic braking systems that will take over to prevent accidents.