Optical guidance systems ride shotgun
Welcome to the world of vehicle assist and automation
By Brian Pessaro
Imagine this scenario. It is January and a Metro bus is heading north on I-35W into Minneapolis during morning rush hour. Traffic starts to back up at the Crosstown as it always does, and within only a few minutes the bus comes a standstill.
Great. Now the driver is going to miss the next timepoint. If this keeps up, the bus may be a full 20 minutes late arriving downtown. Passengers start to grumble and start whispering to one another.
“Why doesn’t he just take the shoulder?” they ask. “After all, Metro buses are allowed to use them during traffic jams.”
But in this case the driver is not willing to take the risk. With all the snow on the ground, he has no way to tell where the shoulder ends. So he stays put. The passengers continue their grumbling as the bus indeed arrives downtown 20 minutes late. If only there were a way he could safely use that shoulder during lousy weather.
Now imagine a different scenario. Heading north on the same corridor again traffic starts to back up. Only in this scenario the driver presses a button that activates the new driver assist system, making the snow no longer a concern as the driver can view the shoulder boundaries digitally projected on a heads-up display.
He moves safely onto the shoulder and starts bypassing the congestion — much to the delight of the passengers onboard. Continuing down the road, the bus starts to drift a little too far left, causing the digital boundary on the heads-up display to flash red as a warning. At the same time the left side of the driver’s seat begins to vibrate as if driving over a rumble strip — another warning cue from the driver assist system. The driver makes a steering correction and keeps moving, arriving downtown on time and unstressed with a happy busload of passengers.
Welcome to the world of vehicle assist and automation (VAA), guidance technologies that provide partial or full control of a vehicle’s movements. In the transit industry, VAA can be used for guiding buses in a narrow lane or shoulder, precision docking at stations or collision avoidance.
As yet VAA is not in widespread use. What little is used predominately by European operators. For example, in Rouen, France transit buses use an optical guidance system that relies on cameras that can read the road stripes and make steering corrections. In Eindhoven, Netherlands, a series of magnetic markers embedded in the road precisely guide the bus into the station. Until recently, only two agencies in the U.S. even attempted to use VAA in bus revenue service.
The Las Vegas MAX bus rapid transit was created with an optical guidance system, but it was quickly discontinued after it was discovered the cameras couldn’t read the stripes in the harsh desert environment. The other system, which was much more successful, was the Cleveland HealthLine bus rapid transit. This used a low-tech form of VAA mechanical guide wheels mounted on each side of the front axle to guide the buses into the stations.
That being said, several locations in the U.S. are giving VAA another try and are experimenting with a variety of technologies.
In Minneapolis, the Minnesota Valley Transit Authority has partnered with the ITS Institute at the University of Minnesota to create a GPS based driver assist system very much like the one described above.
In California and Oregon, Caltrans has partnered with the engineers at PATH at UC Berkeley to develop a magnetic based guidance system. It plans to use it in two places. AC Transit in the San Francisco Bay area will use it to guide a bus on an HOV lane across the San Mateo bridge and through a narrow toll plaza. Lane Transit District in Oregon will use it for precision docking on its EmX bus rapid transit system. Finally, the San Diego Association of Governments plans to start a new bus on shoulder service on I-805 between South Bay and University Towne Centre that will include buses equipped with optical guidance and adaptive cruise control.
The Federal Transit Administration (FTA) has asked the National Bus Rapid Transit Institute to evaluate the impacts of technologies on bus revenue service. Researchers will looking at customer and bus operator satisfaction, efficiency and productivity, maintenance, and safety, as well as how the technology performed.
Brian Pessaro serves as senior research associate for the National Bus Rapid Transit Institute.