United Parcel Service (UPS) and Federal Express are beginning to switch out old diesel-powered delivery vans from their combined fleets of 100,000 vehicles to testing a variety of cleaner fuels and technologies, according to BusinessWeek. The cleaner fuels and technologies include compressed natural gas, diesel-electric hybrids and hydrogen fuel cells. Although the push to cut emissions — trucks produce more than 30 percent of urban smog — is part of the reason, the biggest motivation is cost savings. While pricey to purchase, these vehicles are cheaper to maintain and operate with hybrids, for example, cutting fuel cost by half, while lowering emissions by 90 percent. Based on these companies' large commitments in clean technologies, other delivery fleets are expected to follow the lead of UPS and Federal Express as prices drop including the U.S. Postal Service which plans to mix hybrids into its fleet of 142,000 trucks. According to experts in the field, the scale of Federal Express's commitment to purchase 30,000 hybrid trucks is likely to help jump-start the commercialization of this technology. Commented Fred Silver, director of business initiatives for WestStart, "FedEx really raised everybody's eyebrows." J.D. Powers Associates estimated there will be more than 500,000 hybrid vehicles on the road by 2008 — 40 percent of them trucks.