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Thursday, September 26, 2013

A Cure for Bus Bunching


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FALL 2013 -- Anyone who has ever waited for what seems like forever for a bus—only to have two or three arrive at the same time—has experienced “bus bunching,” a seemingly intractable problem for transit agencies and one that leaves bus patrons seething.

Now an ITS doctoral student and two transportation alumni, along with their professor, have devised a novel and practical solution to bus bunching. The system recently completed successful testing in a mid-size city in Spain.
The four—doctoral student Juan Argote, ITS alums Dylan Saloner and Ethan Xuan, and Professor Carlos Daganzo—have also formed a benefit corporation, VIA Analytics, to market their new product, which they have appropriately named “Tempo.”
Bus bunching occurs when one bus begins to fall behind due to traffic or an unusually large number of passengers at one stop. As it gets to each stop later and later, there are more passengers waiting to board, which puts the bus even further behind schedule.
At the same time, buses that follow have fewer passengers to pick up at each stop, and they gradually gain on the slower bus. And when buses fall far behind schedule, dispatchers must often send extra buses into service, which is costly.
Think of it this way: If a transit system were an orchestra, the conductor would keep each musician playing at a steady pace. The violins and the percussion, the brass and the wind instruments would all play their notes together and at the right time following the conductor’s baton.
Like a conductor’s baton, Tempo helps transit systems and its “orchestra,” the bus drivers, move together.

From theory to reality

Two years ago, the three transportation students were sharing office space on the fourth floor of McLaughlin Hall when they became interested in turning theory—a control algorithm originally developed by Professor Daganzo, then improved by former ITS Ph.D. student Josh Pilachowski, and finally, refined by Argote and Xuan—into reality. 
“What Carlos and Josh had done was significant,” explained Argote. “They went from discrete control to something that is continuously applied.” But that work was done at the theoretical level.
With Daganzo’s blessing, Argote, Xuan, and Saloner began working four nights a week and one day each weekend to refine the algorithm and then write the software. In a matter of months, they were able to turn the control algorithm into a practical tool that could control buses running both on a schedule or at regular intervals.
Using off-the-shelf Android tablets, Tempo allows dispatchers, but more importantly, bus drivers to continually monitor whether they are ahead or behind schedule.
Tablets are mounted in the bus so drivers can easily keep track of when they’re running ahead or behind schedule by glancing at the colored bars, each representing a minute, instead of conversing with dispatchers. Red bars tell drivers to slow down, green bars to proceed normally. The blue bars indicate the driver is on schedule.
“This seems very simple, but coming up with the interface was a pretty complex project because we had to devise something that both drivers, inspectors, management and all layers of the transit agency could agree upon, something that could be understood quickly and intuitively,” said Argote.
Juan Argote holds Tempo, a tool whose colors help bus drivers know when to speed up or slow down to avoid bus bunching. 
For the driver, Tempo is an assistance tool that provides recommendations to speed up or slow down based on the state of the entire bus system. Additionally, Tempo detects when the bus is at a station. “If needed, it displays a countdown timer designed to optimally balance passengers’ travel times and wait times,” added Saloner.

The Spanish experiment

San Sebastian, Spain, an idyllic seaside city near the French border, has a forward-thinking transit agency, Dbus  with 110 buses serving a metropolitan area population of about 400,000.
By chance, the transit agency’s president, Gerardo Lertxundi, had seen a newspaper interview with Professor Daganzo, who was in Barcelona in March of 2012 to receive an honorary degree.
The two discussed the students’ bus-bunching project, and Daganzo suggested the agency talk to Argote, who is Spanish, and would be in Spain a few months later. The discussion went well.
“This transit agency is way ahead of most other agencies and is a real arrowhead of ITS development in transit. It was a perfect match for us,” explains Argote.
Tempo helped the bus line achieve an on-time performance index of better than 80 percent at all stops. 
In the winter of 2012, Argote and Saloner installed the tablets in 16 buses on two lines to start the data collection process.  Argote returned again in April 2013 to help the transit agency test the new system. The researchers were pleased to learn that Tempo was able to provide better adherence to a schedule without affecting the line’s speed.
“This is important because there is always a trade-off between regularity and the speed of service,” said Argote.
They also determined that Tempo helped the bus line achieve an on-time performance index of better than 80 percent at all stops. Moreover, the variance of the deviation from schedule was reduced to between 30 and 60 percent, which resulted in an approximate 10 percent decrease of the system’s passenger waiting time.
Via Analytics was established as a benefit corporation, a new corporate form recently created that provides a dual mandate to allow the corporation to consider both profits and social benefits in its decisions.
In September, Dbus expanded Tempo to a third line. In October, Via Analytics and Dbus will present the final results of the Tempo experiment at San Sebastian’s city hall.

Improving Berkeley’s campus shuttle system

In the meantime, the new company is venturing into several other areas of public transit.
They are in discussions with Bay Area transit agencies to implement the Tempo system in their fleets.
They are also developing a new product to help bus drivers drive “greener” by providing feedback from the engine as they brake and accelerate.
Closer to home, they are developing a real-time passenger information system for the UC Berkeley campus shuttle, which moves students, faculty, and staff around the campus perimeter. The small UC Berkeley shuttle system offers a good environment for experimenting with new technology solutions.
As part of that project, the Berkeley researchers will make their passenger information code open source, and will soon announce a competition open to all to equip the little shuttle system with “the best passenger information system in the world,” says Saloner.
  Ethan Xuan, Juan Argote, Dylan Saloner and Professor Carlos Daganzo, founders of Via Analytics