As snow fell and rush-hour gridlock worsened on Cedar Avenue S., bus driver James Geiger couldn't see the road markings beneath the snow and slush -- but he kept rolling right down the shoulder.

Other bus drivers, sensing a harrowing ride down the narrow strip, had pulled back into traffic. Geiger, however, was piloting a Minnesota Valley Transit Authority (MVTA) bus through a virtual world, projected before his eyes on a drop-down viewfinder.

His bus was equipped with a new navigational system designed at the University of Minnesota. Using a combination of GPS, laser sensors and visual and tactile alerts, the system aims to help drivers navigate shoulders where there is little room for error.

In some places, buses that are 9 1/2 feet wide, including their mirrors, run on shoulders that are 10 1/2 feet wide.

"We're not steering the bus for them. The driver's job is to control the bus," said Michael Abegg, planning manager at MVTA. "We're going to provide assistance to the drivers, comfort."

With that extra reassurance, MVTA, the south-metro suburban transit provider, hopes that drivers will have the confidence to stick to the shoulders, move quickly and improve reliability.

That will be especially important when the metro area's first bus rapid transit corridor opens on Cedar Avenue in Lakeville, Apple Valley, Eagan and Bloomington next year. The busway is meant to mimic light rail, but with buses running on the shoulder between stations instead of trains on a track.

Louis Sanders, director of technical services for the American Public Transportation Association, said transit providers nationwide are using technology to improve passenger safety, speed and reliability on buses. In California, another system to guide buses is being developed using magnets embedded in the road.

"There are all kinds of things going on in the bus world," he said, noting that the U, in particular, is known in the field. "They're really one of the leaders in this development process."

Virtual rumble strips

Ten buses from the MVTA fleet are testing the Driver Assist System technology, developed in the Intelligent Vehicles Laboratory at the U.

When in use, a half-silvered mirror hangs in front of the bus driver's face, allowing the driver to see through to the road with the glowing outline of the shoulder imposed on top it.

GPS and a database of the bus route -- in this case, Cedar Avenue -- tracks the bus' position 10 times per second, accurate to within 5 to 8 centimeters. With that information, the system knows where the bus is and in which direction it's headed.

If the driver strays too far left or right, the stripe on the screen turns from white to red. Then the driver's seat vibrates, like a virtual rumble strip, on the side they are approaching. Finally, a bit of resistance on the steering wheel urges the driver to correct the bus position.

MVTA built a simulator, complete with a mockup of a bus cab, to test the technology and train drivers.

Some are resistant to the video game-like technology, but drivers with technical aptitude tend to pick it up quickly.

Craig Shankwitz, director of the U's Intelligent Vehicles Laboratory, said that even a couple of years ago, what the MVTA is doing would be impossible. "This is the first application where the general public is on the vehicle," he said. "We've been able to address every one of the shortcomings that we had when we first started."

An earlier version of the Driver Assist System, in development since the early 1990s, has been used on snowplows in Alaska and in a smaller pilot on a couple of plows, a State Patrol car and a Metro Transit test bus about 10 years ago.

Bob Gibbons, a spokesman for Metro Transit, said the technology was well received during that test, even in its rudimentary form.

"It wasn't ready for prime time when our part of the research was done," he said, noting that the GPS signal would be lost when the buses passed under bridges. "We're happy to see that it has advanced to the point where it's actually entering service now."

Transit agencies around the country will be paying attention to MVTA's test fleet, with a particular eye to how cost-effective it is.

It cost about $5 million for the simulator, training, technology development and equipment for 10 buses. The funding came through a federal grant to improve transit and relieve congestion in the Twin Cities.

Abegg said the buses will keep the DAS system as long as it's useful. The agency will pay special attention this year to driver reviews and how much time it saves. "It's not cheap," he said. "If we find the benefits are quite large, it will begin to justify the costs."

So far, bus driver Geiger is a fan. "I wasn't 100 percent sold until I had to use it in that snowstorm," he said. "It proved itself."

Katie Humphrey • 952-882-9056