Sure. In the early days, in the late 1990s and early part of this century, many of the bus fleets, some of the refuse transfer fleets, etc., were doing it for environmental standards, because in some of these jurisdictions, like Los Angeles, or Beijing in the Olympics, for example, they were under very strong pressure or they had mandates to reduce their emissions footprint.
More and more, companies are choosing this because of the green advantages, but the principal reason for making the switch is the economic advantage. The green comes with whatever intangible value it carries in North America today, or in some cases if they're in jurisdictions like California, which has the low carbon fuel standard and other things like that. There is also the tangible value of reducing their greenhouse gas emissions and their carbon fuel use.