nationwide. STI officials noted in a recent earnings report that their fuel costs have barely increased despite crude oil prices rising 40 percent over the past year, thanks to the company’s efficiency programs and fleet management. Driver behavior also makes a difference of up to 30 percent in fuel economy, according to Childers. “It is important for drivers to accelerate
slowly and feather the brakes to enhance fuel economy, especially with newer-mod- el buses,” he said. “If the bus has an ‘econ- omy’ feature, engaging that will greatly improve fuel efficiency as well.”
OEM ROLES Manufacturers are improving the
aerodynamics of bus designs that have changed little over decades, offering potential fuel savings. Trans Tech Presi- dent John Phraner said contractors have reported that “Trans Tech school buses go over 2 miles per gallon more than similar buses in their fleet with savings of upwards of $1,500 a year per bus in fuel costs,” while also getting compliments as being “the nicest-looking Type A school buses on the road.” But since buses typically drive slowly, in traffic and constantly stopping and starting, aerodynamics do not change the equation like they would for vehicles on highways. Charles Chilton, director of integrat-
ed product development for IC Bus, explained that aerodynamics are import- ant when driving over 55 mph. Between 35 and 55 mph, tire pressure is the most important factor. When driving under 35 mph, engines have the biggest impact on fuel economy.
Leading clean diesel engines—like the mainstay Cummins B6.7 and the new De- troit DD5 and DD8 engines—“are built with a high pressure common rail fuel system that provides significant improve- ments in fuel economy,” Childers said. “A high-performance engine brake allows braking to occur at lower engine speeds where less fuel is being used. At the same time, the variable-speed fan and advanced cooling system generate airflow to the engine at precise times while operating without the fan running constantly.” For Trans Tech, fuel economy is
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improved by not only aerodynamics but their use of “state-of-the-art power trains, new HVAC technologies, lighting and electrical efficiencies and diverse fuel options,” as Phraner put it. Oyster outfits Apple’s buses with higher-than-standard horsepower and torque ratings, and gears them at higher levels than usual. “Tis configuration allows the engines to operate at a lower RPM, thus reducing the fuel burn rate,” he said. Ultimately, Childers added, “It’s imperative for school districts to work one-on-one with their dealers to spec new school buses for optimal fuel economy based on the perfor- mance needs of the district. ●
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