Last year, when the King County, Wash., Department of Transportation fleet administrators began evaluating new utility trucks to replace an aging vehicle, they considered a new hybrid model that was being developed. The truck would operate like a standard diesel vehicle during steady driving conditions above 30 miles per hour, but below that speed, it would use a combination of diesel and electricity, automatically switching between the two modes as needed. On a job site, the vehicle's 340-volt hybrid battery would power auxiliary equipment, such as an aerial boom, so crews would not have to run the diesel engine continuously.

The county has been pursuing alternative fuel technologies, and its experience with its existing hybrid fleet vehicles, which now include 115 Toyota Priuses and 41 Ford Escape hybrids, had shown positive results since the county began using them in 2001. “We've had very good success with those, and I felt confident that we would see the same results,” says Bob Toppen, equipment manager for King County Department of Transportation, Fleet Division.

After meeting with the truck manufacturer, Kirkland, Wash.-based Kenworth, King County agreed to be the first government agency to test a medium-duty hybrid truck for utility operations. In September, the hybrid, equipped with a 50-foot boom and a utility bucket, joined the county's fleet of 10 other utility trucks. The engine is fueled with B-20 biodiesel (20 percent biodiesel and 80 percent ultra low-sulfur diesel).

County utility crews have been using the truck daily, primarily for traffic signal maintenance. Its fuel economy so far has been 30 percent better than other light-duty fleet vehicles. The fuel economy allows crews to remain in the field for a longer time between refueling, and it extends the truck's maintenance cycles. The truck also is quieter. “When we are called out on emergency repairs in the middle of the night, by not having to run the engine, we're not waking up the neighborhood with the engine running all night,” Toppen says.

The county purchased the $208,000 truck without a premium charge for the Kalamazoo, Mich.-based Eaton hybrid power system because the county agreed to demonstrate the vehicle to other fleets. “We have showcased the truck at several media and technical events and have people come and see it operate because it is pretty unique, and the aerial boom application is ideally suited for the hybrid system,” Toppen says.

Since testing the vehicle, the county has ordered two more trucks with the same hybrid technology (one recovery truck and another aerial lift truck) from other chassis manufacturers. The hybrid technology currently increases truck prices $45,000, and the county has received grants to help offset those costs.

Project: Hybrid utility truck pilot project

Jurisdiction: King County, Wash.

Agency: Department of Transportation

Vendor: Kirkland, Wash.-based Kenworth Truck Co.; Kalamazoo, Mich.-based Eaton Corp.

Date: September 2007

Cost: $208,000