At a landfill near Livermore, Calif., refuse trucks roll up to the dump, drop off trash and refuel with methane generated by the garbage heap.
At the U.S. Department of Energy, more than 7,000 government vehicles run on propane.
And from hybrid taxis in New York to compressed natural gas trucks at U-Haul, virtually every sort of unconventionally powered vehicle can be found in U.S. fleets -- the real-world workhorses for stress-testing green vehicle technology.
Fleets offer a sharp contrast to the retail market, where automakers selling green vehicles must overcome serious obstacles, such as enormous fueling infrastructure needs and ingrained consumer habits.
That makes fleets an appealing initial market for green vehicles -- and, automakers hope, a steppingstone to retail success.
"We are not restricting the availability of any of our technologies to simply the fleet customer," says Gerry Koss, Ford Motor Co.'s fleet marketing manager. "But near term, the interest and demand by fleet may be more than retail."
Ford will bring out the electric Transit Connect van this year, followed by a Focus EV in 2011 and a plug-in hybrid in 2012.
Steven Schneider, CEO of electric vehicle maker ZAP, says fleets that have their own recharging stations are a prime EV market. Consumers worried about limited range will adopt EVs slowly, Schneider says.
"There's no way to put in enough infrastructure in the early years to come that you would not have range anxiety."
But it's not a given that fleet sales will lead to retail success. CNG vehicles have been used in fleets for years without penetrating the consumer market.
Fleet sales, in other words, could be a dead end.