Libraries, Food Banks Benefit from Transportation Modeling

Karen Smilowitz of Northwestern University helps non-profit organizations streamline their work. CREDIT: Andrew Campbell, Northwestern University

This Behind the Scenes article was provided to LiveScience in partnership with the National Science Foundation.

For industrial engineering professor Karen Smilowitz, the best part of her job is finding new ways to apply her specialty — transportation modeling — to problems that benefit humanity.

"Industrial engineering is not just taking a calculator and a stop watch and hanging out in a factory," she says. "There’s a lot more we can do to help society by applying our research."

Smilowitz, the Junior William A. Patterson Chair in Transportation at the McCormick School of Engineering and Applied Science at Northwestern University, researches how to optimize how freight is moved in an area, including how to reduce miles for trucking or how to get two companies to work together to pool their resources and lower costs.

But recently, she has been using her research to solve problems in a new area — nonprofits.

An NSF CAREER awardee, Smilowitz has worked with both a local suburban library system and a local food bank to maximize how books and food are distributed. Besides having a humanitarian problem that they often don’t have the budget or knowledge to solve, these organizations have different needs than for-profit companies.

"When you have a nonprofit, the goals change," she says. "You can’t just take a commercial model and apply it, since maximizing profit and minimizing cost aren’t necessarily the goals."

In the library system, vans visit each library five days a week to pick up and drop off book requests. But as the economy went down, demand for library books went up — yet the library’s budget was stagnant. That meant it was no longer feasible to provide the service every weekday.

So Smilowitz and her graduate students, along with visiting scholar Michal Tzur from Tel Aviv University, set to work finding the best solution to the problem. But making a model to make a route efficient means dealing with more than just problem factors — it means taking into consideration human factors as well. Library employees wanted to see the same driver every day, and it was too complicated to do away with a central depot where books go for sorting in order to maximize efficiency. It also didn’t work to lend or borrow from certain libraries — library employees didn’t want any branch known as a big loaner or borrower.

What researchers eventually found was that they actually could reduce travel costs by increasing library visit frequency. That way, instead of only going to certain distant libraries every other day, the route was optimized so drivers would go to each library three days a week, and every library could have greater service.

“We found this counterintuitive result where we can reduce transportation cost and increase service,” she says. “This opportunity is unique to nonprofits.  In a for-profit setting, if you don’t pay for a level of service, you don’t get it. But we uncovered this new variation of the vehicle routing problem, which is really exciting. There is also this interdependency in how often you go and what you pick up, since if you go less frequently, books will accumulate. So we had some interesting formulation issues trying to keep things linear.”

Smilowitz and fellow Northwestern professor Seyed Iravani, and their students, are working with a local food bank in Chicago, where the bank’s food distribution system collects food from restaurants and grocery stores and distributes it to soup kitchens and homeless shelters. The organization wanted to know the best way to pair up donors and recipients and how to best design delivery routes to serve people.

“If this were a for-profit company, and you wanted to minimize cost, instead of giving to five agencies, you would just give to the first couple on your route,” Smilowitz says. “But that’s not equitable or sustainable. The food bank needs these agencies to be sustainable so they can distribute food and give everyone their fair share of supplies.”

This problem, called sequential allocation, has been studied for years in for-profit settings. But when the objective becomes different, the math gets messier.

“We looked at the properties that were performing well for small examples to see how these could converge on what we wanted to do,” she says. “From there we came up with different variations and analytical results. We want problems that we can solve. That’s really where the art of operations research comes in: creating a model that will solve not only this problem but similar general problems as well, so other people can use it.”

Smilowitz enjoys the challenge of taking well-known models and reformatting them for the non-profit sector.

“It’s great to work with organizations that need our help,” she says. “It’s a great example of finding something you’re interested in and linking it to your research.”

Editor's Note: This research was supported by the National Science Foundation (NSF), the federal agency charged with funding basic research and education across all fields of science and engineering. See the Behind the Scenes Archive.