Tag: school districts

OM in the News: Using OM to Fix School Bus Routes

Last year, more than 30,000 students in the Boston Public Schools rode 650 buses to 230 schools at a cost of $120 million. In hopes of spending less this year, the school system offered $15,000 in prize money in a contest that challenged competitors to reduce the number of buses. The winner, reports The Wall Street Journal (Aug. 12-13, 2017), was MIT’s Operations Research Center, which devised an algorithm that drops as many as 75 bus routes.

The school system says the plan, which will eliminate some bus-driver jobs, could save up to $5 million, 20,000 pounds of carbon emissions a day and 1 million bus miles each year. The computerized algorithm runs in about 30 minutes and replaces a manual system that in the past has taken transportation staff several weeks to complete. “They have been doing it manually many years,” said the MIT Center co-director. “Our whole running time is in minutes. If things change, we can re-optimize.”

The task of plotting school-bus routes resembles the classic exercise known as the Traveling Salesman Problem (TSP), where the goal is to find the shortest path through a series of cities, visiting each only once, before returning home. Although we don’t cover TSP in the written text, we do so in our MyOMLab Tutorial called Vehicle Scheduling & Routing.

Classroom discussion questions:

  1. Provide other applications of TSP.
  2. How does this scheduling problem differ from that of airlines scheduling planes and crew?

OM in the News: Sustainability Hits the School Bus Fleet

Blue Bird factory workers installing windows on a bus in Fort Valley, Ga. School districts are increasingly ordering propane-fueled buses.
Blue Bird factory workers installing windows on a bus in Fort Valley, Ga. School districts are increasingly ordering propane-fueled buses.

For many Americans, propane is that stuff from Home Depot that fuels backyard barbecues. But in a growing number of cities across the country, it is what gets children to school. Of the top 25 school bus markets, 19 have propane-fueled vehicles in their fleets, including New York, Chicago, Houston, Los Angeles, Miami, Philadelphia and Phoenix. Boston just bought 86 of the alternative-fuel buses for the fall, while in the Mesa County Valley district in Colorado just signed a 5-year, $30 million contract that includes 122 propane buses.

And southeast of Atlanta, Bibb County school administrators are so happy with the 33 buses they started running last year that they have ordered 20 more. “They’re healthier, they’re cleaner burning, they’re much quieter than the diesel option,” said the transportation director. “Right now, it’s projected that over time we’ll see significant savings.” Burning propane reduces greenhouse gas emissions by 22% compared to gasoline-powered buses or 6% compared to diesel.

The number of alternative fuel fleet vehicles on the road has steadily increased in the last decades, reaching nearly 1.2 million in 2011 from 247,000 in 1995, reports The New York Times (May 22, 2015). Most run on ethanol, propane, compressed natural gas and electricity. The fuel, a byproduct of oil refining and natural gas processing, is abundant and less expensive than diesel, running about $1 less per gallon equivalent. School districts using the fuel have generally been able to claim a federal alternative fuel tax credit of 50 cents per gallon. The buses, which now represent about 20% of manufacturer Blue Bird’s business, come at a premium — about $103,000, roughly $15,000 more than a diesel model — but they are cheaper to operate and maintain, requiring less oil and fewer filters than conventional vehicles.

Classroom discussion questions:

1.Have your students prepare a life cycle analysis, as we present in Supplement 5, comparing the propane vs. diesel options. Gather data from the internet on costs and mileage.

2. What are the advantages of propane over diesel or gas buses?