When Mayor Paul Soglin asked Madison's bus company to transition to low- or no-emission vehicles for half its fleet by 2035, two REDA graduate students got an opportunity to carry out a project to benefit the community. Oliver Su and Qifan Hu used analytical tools from their courses to compare the costs and benefits of replacing diesel with electric vehicles. They found that electric buses, despite their higher cost, would pay for themselves about half-way through their lifetimes.
"We are very thankful to have such a report," said Metro's transit planner Kate Christopherson. "We're evaluating the options for electric vs. other propulsion systems for our buses, and we will use this report in our evaluation."
Each day, a Madison Metro bus travels about 250 miles, transporting passengers over a 20-hour period. Ten percent of Metro's fleet of 215 buses are hybrid vehicles that burn less gas but cost more to maintain than the remaining diesel-powered buses. With a price tag of more than $1 million, an electric bus costs three times more than a diesel, but their fuel and maintenance savings do much to offset that big investment.
Then there are the environmental and health considerations that factored into the students' analysis.
"We were surprised that electric buses do not have an obvious advantage in carbon and health costs," they said. By looking beyond the direct costs, such as purchase price and fuel, they found that the "emissions footprint" from generating electricity somewhat reduced the benefit of electric buses. "In Wisconsin, the major source to generate electricity is coal. If natural gas and renewables are more applied in generation, the advantage of electric buses will be more obvious," they explained.
Nevertheless, "electric buses appear to be a leading contender," said Christopherson. "We are hoping in our next 5-year bus procurement process, to be released in the next year, to have an option for electric buses so that we might start purchasing them in the next 5-7 years."
Madison joins other cities across the U.S. exploring alternatives to burning fossil fuels for public transportation, and the REDA study will help inform city decision-making. "Madison Metro Transit will save money in the 15-year bus lifetime if electric buses join the fleet. At the same time, the health of people in Madison will be improved," by better air quality, write the study authors.
The idea for the project took root at the campus Energy Hub conference last fall, when REDA Coordinator Bethany Glinsmann met Chuck Kamp, Metro Transit General Manager, who likes to partner with students. Jeff Butler, Metro's maintenance manager, provided the student team with background information and data for the study.
"We were really glad to collaborate with Metro to give our students an interesting real-world project that will help the company with future bus purchasing decisions," said REDA Director Bill Provencher. The project was part of REDA's capstone practicum, in which students analyze real data to solve research problems.