One of the major shortcomings with current green fleet modernization is its lack of focus on the total environmental impacts (or "carbon footprint" if we wanna get really technical) of its operations from a lifecycle analysis standpoint.
In other words, how can we calculate the energy savings or emissions reductions that take place apart from the emissions created by vehicles themselves? After all, vehicles not only produce emissions from the fuel they burn, but require a series of maintenance products that consume a variety of plastics and hazardous wastes with significant environmental impacts of their own. Even recycling plastic or paper products creates harmful emissions that are seldom included in lifecycle analysis. This recognition has led to the development of "Sustainable Purchasing" policies in many cities including Seattle, which attempt to procure maintenance and supply products from the most environmentally-friendly source. However, green fleet modernization schemes like Evergreen Fleets have yet to incorporate sustainable purchasing into their official Best Practices.
This story from Inhabitat examined an interesting project recently completed by students at Northeastern University, under guidance of Professor Yiannis Levendis. Their plastic waste compactor converts plastic into electric energy without harmful emissions of traditional recycling. Over 20 years in development, this type of compactor could be very useful as a new Best Practice to incorporate in green fleet modernization.
Photo Credit: Mary Knox Merrill