Now, the leading school bus manufacturer, IC Bus, is producing the nation's only line of hybrid school buses. These hybrid school buses improve fuel efficiency by up to 70 percent and also reduce diesel emissions by up to 70 percent. The school buses are "plugged in" at night, charging the electric motor that is part of the hybrid system. The electric motor and the diesel engine work effectively together during operation of the school bus, resulting in the lower emissions and increased fuel efficiency.