ANN ARBOR—Adding to one of the largest university alternative energy vehicle fleets in the nation, the University of Michigan announced it is purchasing seven diesel-electric hybrid buses.

By the end of FY 2012, one in six buses on campus will be a hybrid. The new buses will begin replacing current buses that run on diesel fuel.

“Adding hybrid buses to our fleet is another step in our commitment to sustainability. Our long-term goal is an entire fleet of highly efficient vehicles,” said Keith Johnson, associate director of transportation operations.

The new 40-foot buses use a roof-mounted battery system to supplement their diesel engines, allowing for better fuel mileage and lower emissions. The hybrid buses get approximately five miles per gallon of fuel?an improvement of 30 percent over a conventional bus.

Hybrid technology is especially beneficial for vehicles that encounter frequent stop-and-go traffic, like campus buses. When the brakes are applied, a generator converts the energy released from deceleration into electrical energy, which is stored in a battery and used when the bus accelerates.

In addition to the new buses, the university has purchased an additional 30 hybrid sedans. The sedans are available to faculty, staff and students for authorized university business travel, both local and long distance.

The university received federal funding to help cover the additional cost of a hybrid over a conventional vehicle.

The university operates one of the largest alternative energy vehicle fleets among universities in the United States, with 545 vehicles running on E-85 fuel, 96 vehicles using bio-diesel, 29 hybrid sedans, and 15 all-electric vehicles. Renewable energy sources comprise 16 percent of the total transportation energy at U-M.

The university’s long-term goal is to replace existing vehicles in its transportation fleet with new alternative energy models when the current vehicles are retired.