The U.S. Environmental Protection Agency has unveiled a first-ever hydraulic hybrid diesel urban delivery vehicle.

The vehicle is a retro-fitted United Parcel Service truck, the EPA said Wednesday.

In laboratory testing, the EPA's patented hydraulic hybrid diesel technology achieved a 60 percent to 70 percent improvement in fuel economy and more than a 40 percent reduction in carbon dioxide emissions, compared to a conventional UPS vehicle, the agency said.