The city has unveiled the first of four plug-in hybrid electric vehicles it will test over the next year.

Specifically, the project will test technology used to convert four existing Priuses in the city's fleet to 100-miles-per-gallon vehicles.

"With gas prices exceeding $4 a gallon and climbing, we must accelerate our efforts to develop clean and cost-effective alternatives to gas-fueled vehicles," said Mayor Greg Nickels. "This project is part of the city's strategy to be on the cutting edge of energy, building and transportation technology, paving the way for others to learn our lessons.

Last October, the city joined with the Port of Seattle, King County and the Puget Sound Clean Air Agency to test the performance of plug-in hybrid electric vehicles in an urban area. With money from the Department of Energy's Idaho National Laboratory matched by the participants, 13 Priuses are being converted to plug-in hybrid electric vehicles. The total cost is $156,000.

The city will operate four of the converted Priuses, King County will operate four, the Port of Seattle will have two and Puget Sound Clean Air Agency will have three. The plug-in conversion kits are provided by A123Systems of Watertown, Mass.

The plug-in vehicle is the successor to the conventional hybrid, which is charged by on-board electrical systems. The plug-in modle has a second "fuel tank" in the form of a longer-lasting battery that can be "filled" from an ordinary socket at a cost equivalent to less than $1 per gallon of gasoline.

Achieving up to 100 mpg, plug-in's are just one more step the city says will fight against climate disruption with the added benefit of ultimately reducing dependence on foreign oil. Expected greenhouse gas emissions from the plug-in Priuses in this demonstration project are up to 50 percent less than conventional Priuses.