PATH Demonstrates Automated Bus Rapid Transit Technologies
by Steven E. Shladover

PATH researchers demonstrated some of the key technologies for automated bus rapid transit (A-BRT) services for invited visitors in San Diego on the weekend of August 23-24. This demonstration continued a distinguished PATH tradition of demonstrating the most advanced ITS capabilities under realistic conditions on full-scale vehicles, and true to that tradition it exceeded the expectations of the visitors.

PATH has equipped three transit buses with the sensing, actuation, communication and computation systems needed to enable them to operate under completely automatic control. At the same time, these buses were equipped with a specially-designed driver-vehicle interface (DVI) system to show how easy it is for the driver to interact with the automation systems, to transfer back and forth between normal manual driving and automation and to initiate automated maneuvers such as lane changing on the highway and precision docking at local bus stops.

The emphasis of this demonstration was showing the realistic opportunities for implementation of the A-BRT technologies to improve transit service and economics. Since the demonstration buses were two standard-size (40 foot) buses powered by compressed natural gas (CNG) and one 60-foot articulated bus powered by a diesel engine, it was also possible to show how the automation technologies can harmonize the performance of these very different vehicles so that they can operate close together in an electronically-coupled "virtual train".

Click Here to see a demo of the Automated Bus Platoon. (Real Video File)

The transit service functions that were demonstrated included:

  • Precision docking of a bus at two different platforms, one representing an in-line platform at a bus terminal and the other representing a curb-side platform requiring an approach with a lane change ahead of a line of parked cars. In both cases, the bus stopped with a gap of less than an inch between the bus floor and the platform, making it easy for one of visitors to roll on and off the bus in a wheelchair. Both the steering and the stopping of the bus were controlled automatically, although initial deployments of this service would probably only use the automated steering function, leaving the full attention of the driver for watching out for pedestrians and passengers.

    Click Here to see a video of Precision Docking (Real Video File)

  • Automatic lane-keeping (or lane assist) of the buses operating in a line-haul mode on the I-15 HOV lanes. This demonstration showed the ability of the automatic steering system to keep the bus centered accurately over the lane, while providing a smooth ride for the passengers. This is an important capability to enable buses to operate in narrow lanes where right of way is costly or unavailable. The driver was able to switch back and forth between automatic and manual steering at will, showing how a driver could override the automatic system when necessary.

  • Automatic lane-changing while operating on the highway, initiated by the driver pressing a button on the DVI. In order for buses to be able to enter or exit from an A-BRT bus-way, or from off-line stations, it is necessary for them to be able to change lanes automatically. This part of the demonstration showed the ability to execute this maneuver repeatedly, with a minimum of effort required by the driver.

    Click Here to see a video of Automatic Lane Changing (Real Video File)

  • Fully automated bus driving. The buses were operated in both low speed (docking) and high speed (highway driving) conditions with fully automatic steering and speed control. Once the driver transferred control to the automated system, he did not need to do anything else until reaching the other end of the HOV lanes, where he regained control. This capability indicated the potential for future operations without requiring a driver to be on every bus operating along a dedicated, protected bus-way. However, the technology is not yet sufficiently mature and fault-tolerant to make it possible for our drivers to leave the driver's seat (except in the limited case of the low-speed precision docking maneuver).

  • Automated "virtual train" of buses. The diesel bus was electronically "coupled" behind one of the CNG buses for a run down the length of the I-15 HOV lanes (8 miles), making use of a "WiFi" wireless data link, combined with forward-looking lidar and radar sensors to detect the gap and speed difference between the buses. The buses ran at separations of 40 m and 15 m to each other and smoothly performed the automatic transitions between these two different target separations. The operations at the 15 m separation showed the potential for automated bus trains to carry very high passenger volumes in the highest- density corridors. With that length of separation between the buses in the "virtual train", and with a long enough separation between consecutive bus trains to ensure that no failure would involve more than one bus train, a sequence of three-bus trains could provide 70,000 seats per hour in one lane, which is competitive with the highest-volume rail transit services.

The visitors who participated in this demonstration included members of the Board of Directors of ITS America and the Program Steering Committee of the Cooperative Vehicle-Highway Automation Systems (CVHAS) pooled-fund project, as well as the attendees of the TRB meeting on "Urban & Community Transit - The Role for Automated BRT". The reactions of the visitors were very enthusiastic. For example, Neil Schuster, the President and CEO of ITS America, said,

"The San Diego demo went very well and I know our members enjoyed it; this is the fourth time I've seen the technology in action, and each time I'm amazed - now I can tell friends I rode in a city bus, going down a real highway at speed, too close to a bus in front of us for a human driver to attempt. For me, the expression on someone's face the first time they comprehend they are in a moving vehicle without a driver is priceless! What a great morning!"

The discussions in the TRB meeting that immediately followed the demonstration were strongly influenced by many comments indicating that the demonstration changed people's minds about what was possible and opened their eyes to new possibilities for using vehicle automation technology to improve transit operations. That, of course, is one of the strongest reasons for investing the effort to present such a demonstration.

The efforts were considerable and involved extensive time spent away from home by a team of more than a dozen PATH research and development engineers, working under the leadership of Dr. Ching-Yao Chan including: Bénédicte Bougler, Fanping Bu, Susan Dickey, Bart Duncil, Anouck Girard, Adam Howell, Paul Kretz, Thang Lian, Joanne Lins, David Marco, David Nelson, Christopher Nowakowski, Daniel Schickele, Bongsob Song, Han-Shue Tan, and Elvin Vedar. Their work schedule was governed by the limited availability of the I-15 HOV facility for testing in preparation for the demonstration. All of the preparatory testing needed to be conducted during the four weekends prior to the demonstration (8 am to 8 pm each day) and during the weeknights in the two weeks immediately before the demonstration (8 pm to midnight). With outstanding cooperation and support from Caltrans District 11 and Division of Research and Innovation (DRI) colleagues, extremely rapid progress was made during that final month of preparations for the demonstration.


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