AC Transit said the testing work was "performed with remarkable precision."
The 60-foot research bus was demonstrated along a one-mile stretch of East 14th Street in San Leandro.
It was embedded with a series of magnets. Special sensors and processors on board the bus detected magnets in the pavement and controlled the steering based upon the information they received.
The driver maintained control of braking and acceleration, but the steering was completely automated, allowing the bus to pull into stops to within an accuracy of 1 centimeter, AC Transit officials said.
At any time, the driver can resume manual control of the bus.
Researchers say such precision docking would help shave seconds off of the time to load and unload passengers at each stop.
Researchers said the savings add up to a significant increase in reliability and efficiency over the course of an entire bus route.
AC Transit officials said precision docking could negate the need to deploy wheelchair ramps and make passenger lines more efficient.
Transit officials said the precisely controlled movement of the bus could reduce the width of the lane required for travel from 12 feet - the current standard - to 10 feet, researchers said.
Caltrans provided $320,000 to fund the Automated Bus Guidance System demonstration project, conducted by the California Partners for Advanced Transit and Highways (PATH) program based at Cal.
"Today's demonstration marks a significant step in taking the technology off of the test track at UC Berkeley's Richmond Field Station towards deployment onto real city streets," said Wei-Bin Zhang of the PATH program. "We have seen increasing interest among transit agencies in this technology because of its potential to bring the efficiency of public bus service to a level approaching that of light rail systems, but at a much lower overall cost."
California PATH researchers have been studying magnetic guidance systems for nearly 20 years.
Transit officials said the technology has already been used in carpool lanes in Southern California as well as for industrial vehicles such as snowplows and tractor-trailers in Northern California and Arizona.
Friday's test run along East 14th Street marks the first time the magnetic guidance technology has been used for transit buses on a public road.
"It is our mission to improve mobility across California, and maximizing transportation system performance and accessibility through this technology helps us to achieve our mission," said Larry Orcutt, of Caltrans. "This technology could convince more people to get out of their cars and onto buses, and as a result, reduce congestion."
Data From 88 Feet of Roadway Can be Read By Sensors in One Second
In the demonstration, sensors mounted under the bus measured the magnetic fields created from the roadway magnets, which were placed beneath the pavement surface one meter apart along the center of the lane.
The information was translated into the bus's lateral and longitudinal position by an on-board computer, which then directed the vehicle to move accordingly.
For a vehicle traveling 60 miles per hour, data from 27 meters (88 feet) of roadway can be read and processed in one second.
Zhang added that the system is robust enough to withstand a wide range of operating conditions, including rain or snow, a significant improvement to other vehicle guidance systems based upon optics.
Researchers also pointed out that magnetic guidance technology allows for a bus to safely follow closely behind another.
Extra vehicles, much like extra cars on light rail trains, could be added during peak commute times, researchers said.
In the East 14th Street demonstration, the magnetic guidance system was only used to control the steering for the bus, but on test tracks it has been used for full vehicle control - including braking and accelerating - creating a true "auto-pilot" system for the bus, transit officials said.
Potential applications for the system include automating bus passage through narrow tollbooths and vehicle routing in bus maintenance yards.
The system could be integrated into traditional bus routes or used as part of more advanced bus rapid transit (BRT) systems that could include a dedicated traffic lane.
Many cities throughout the world, including 20 in the United States, have deployed some form of BRT, although only a few include dedicated bus-only lanes.
Friday's demonstration included a special industry presentation attended by dozens of representatives from California transit agencies interested in whether PATH's magnetic guidance technology might fit with their own BRT plans.
On some routes in the Bay Area, AC Transit currently operates a version of bus rapid transit that includes electronic signs informing riders of when to expect the next bus.
However, the transit agency is currently in the midst of preparing an Environmental Impact Report for a proposed BRT project that could include bus-only lanes along an 18-mile stretch from downtown Berkeley near the UC Berkeley campus south to San Leandro's Bay Fair BART station.
"We are continually investigating new technologies to improve the performance, safety and comfort of buses," said Chris Peeples, president of AC Transit's board of directors. "The system has the potential to make bus rapid transit routes - particularly those that involve bus-only lanes - as efficient as light rail lines, which in turn will make buses more effective in getting people out of their cars."
AC Transit puts the cost of its BRT proposal at $273 million, while a comparable light rail system would cost around $2 billion.
Zhang said that adding the magnetic guidance technology to AC Transit's proposed BRT project would help it run more like a light rail system for an additional $5 million.
The Valley Transportation Agency has also compared the costs of BRT and light rail systems for its planned Santa Clara Alum Rock Transit Improvement Project.
The estimated cost for BRT came in at $128 million, compared with $393 million for light rail.
AC Transit is joining Caltrans and the U.S. Department of Transportation in funding the next stage of the Automated Bus Guidance System project as it becomes part of the federal Vehicle Assist and Automation Program.
The project will expand to AC Transit routes along Interstate 880 and the San Mateo Bridge, and to a dedicated BRT route in Eugene, Ore.
"Ultimately, it's up to the community to decide which transit option is best for its members," said Zhang. "Our job is to develop the technology that can help improve whatever form of transportation is used."