In the past decade, Metro Transit has purchased well over 100 hybrid buses (see Figure 1) that today represent over 15% of its fleet. The effort is part of a systematic initiative called “Go Greener” aimed at reducing emissions and lessening dependence on fossil fuels. Although the fuel costs of Metro Transit’s hybrid buses can be up to 25% less than those of conventional diesel buses, the upfront costs are much higher – up to $170,000 per bus. For the latest purchase of hybrid buses, Metro Transit received a Federal Transit Authority grant called a TIGGER (Transit Investments for Greenhouse Gas and Energy Reduction), which covered 80% of the funding for the new buses.
|Figure 1 (image via Metro Transit)|
New York City hasn’t purchased a hybrid bus in three years, and is thinking about retrofitting some of its current hybrid engines with diesel engines because of the high maintenance costs of hybrid engines that, in their opinion, don’t necessarily outperform conventional diesel engines. The Ann Arbor Area Transportation Authority (AAATA) is currently debating whether to purchase new hybrid buses without government assistance (due to the current unavailability of grant funds) or revert back to conventional diesel buses.
The benefits of hybrid buses include lower levels of greenhouse gas emissions compared to conventional diesel buses, a regenerative braking system, and improved fuel economy. But at a cost of $500,000 to $800,000 per bus, are the benefits of a hybrid bus worth the hefty price tag?
According to a report commissioned by the AAATA, the upfront cost of a conventional diesel bus is about $455,298, while the upfront cost of a hybrid is about $650,763. Even though hybrids are saving the AAATA a substantial amount of money on fuel (see Figure 2), the efficiency benefits of hybrids erode on routes with higher speeds and infrequent braking, and in the end, the AAATA estimates the total life-cycle cost of a conventional diesel bus is $761,559 versus $948,264 for a hybrid – a difference of $186,705 per bus.
|Figure 2 (image via AAATA)|
Even though hybrid buses saved the Metropolitan Transportation Authority (MTA) approximately 50,000 gallons of diesel fuel per bus during their heyday, today, officials argue that the new diesel buses can exceed the emissions profile of a hybrid bus, and on high speed routes, diesel buses simply “work better.”
It is hard to blame the communities of Ann Arbor and New York City for their hesitation to invest in new hybrid buses due to their higher cost, keeping in mind that government grants are not always available. Yet whatever communities may save in upfront costs now if they choose to invest in diesel buses is counteracted by the irreversible effects to our environment for years to come.