Hybrid and Fuel-Efficient Vehicles
City Engineering has recently purchased several Ford Hybrid Escapes and Honda Fits to add more fuel-efficient vehicles to the fleet. In addition, Fleet Services plans to add more fuel-efficient vehicles to the fleet as older vehicles are cycled out.
In 2007, the City of Madison purchased 5 hybrid-diesel buses. These five buses were paid for through 80% federal funding and 20% local funding. The local funding was paid though a partnership with UW-Madison, with two of the buses designated for UW routes. The nickel metal hydride batteries are expected to last six years. The big benefits with hybrid-diesel buses are reduced fuel consumption with 25-50% fuel economy improvement and lower emissions including up to 50% reduction in Nitrogen Oxide (NOx) and up to 90% reduction in Carbon Monoxide (CO), Particulate Matter (PM) and Hydrocarbons (HC).
The hybrid system computer determines the most efficient way to propel the bus in a forward motion. The computer takes inputs from different components to determine which mode of power to use. The computer can use engine, electric motors, or a combination of both to move the bus. The bus primarily uses battery power to accelerate to 25mph at which time the engine will assist in maintaining vehicle speed.
The system also takes the energy from deceleration and turns it into electrical energy, which is then stored in the vehicles Nickel Metal Hydride (NiMh) batteries. Electrical energy is then routed back to the drive unit to propel the bus in a forward direction.