Metrobus Fuel Efficiency on the Rise
In recent years, the fuel efficiency of the Metrobus fleet has significantly improved, reducing Metro’s fuel expenses, and improving Metro’s environmental sustainability.
Over the past 8 years, the average fuel economy of Metro’s bus fleet has increased by 27%, from 2.96 miles per gallon (MPG) to 3.76 MPG today. The chart at right illustrates this trend, using actual odometer and fuel readings which are gathered and stored by our bus technology group.(Note that these figures include the consumption of compressed natural gas [CNG], expressed as gallon-equivalents. The slight dip in FY2011 is the result of some data loss during a transition to an electronic mileage tracking system.)
What is Causing this Trend? This steady increase in fuel economy is generally the result of technological improvements in the fleet. Metro has been replacing older standard diesel buses with newer diesel-electric hybrid, CNG, and clean diesel models. In particular, introducing diesel-electric hybrid buses to the fleet has helped push up the average: on the streets today, our diesel-electric hybrid fleets are achieving average mileage of 4.49 MPG. Metro purchased its first hybrid bus fleet in 2006, and today these buses provide 41% of Metro’s bus vehicle-miles.
Of course, this is only a fuel efficiency analysis, and more goes into decisions about fuel technologies. Generally, Metro’s experience has shown that lifecycle costs (total capital + fuel + maintenance costs spread over the bus’s lifespan) are comparable across the different technologies, with both hybrids and CNG buses barely more expensive than diesel.
That Seems Low! When average cars get 25 MPG or more, 4 MPG for a bus may not seem like much. But most heavy-duty transit buses operating in a dense downtown environment get around that amount, and in fact Metrobus compares fairly well to other transit agencies in this regard. The chart below compares Metrobus to several other big-city transit agencies for calendar year 2010 (the latest data available in the National Transit Database).
What Does this Mean? These improvements in fuel efficiency have meant that our buses can travel the same distance while consuming less gas, reducing fuel costs and emitting fewer greenhouse gas pollutants into the air. Altogether, Metrobuses drive nearly 50 million miles per year, and we typically budget around $40 million per year for diesel and CNG fuel. If diesel costs $3.00/gallon, a change in fuel economy of 0.5 MPG fleetwide equates to approximately $6 million in fuel costs per year. So, small changes in fuel economy have made a big difference.