Jeff Cochrane wears black Reeboks to work. The mail carrier walks seven to nine miles a day and likes the variety of delivering the day's bills, pizza coupons and birthday cards. His vehicle was parked Monday as he delivered mail to apartment buildings on Kimberly Drive in DeKalb. It's called a park-and-loop route, where carriers will park their vehicles and walk a section, then drive to the next section. It's not a new delivery method, but it has become an increasingly important way to deliver the mail as post offices try to save on fuel costs. Fuel prices have “attacked” the U.S. Postal Service, said Tim Ratliff, a spokesman for the agency's northern Illinois district. The Postal Service operates the largest civilian vehicle fleet in the world with vehicles driving more than 1.2 billion miles each year, Ratliff said. Every time motor fuel increases a penny, costs increase more than $15 million each year, he said. Cochrane's five routes are either park-and-loop, curb delivery or driving and parking at each stop. “I have a nice mix with mine and I like it that way,” he said. Each post office studies routes and capabilities to save fuel costs, acting DeKalb Postmaster Sharon Myers said. One thing the DeKalb post office is trying to explore is having more routes that can be walked rather than driven. “We look at every cost-saving thing now,” she said. Nationwide, a third of all deliveries are made on foot. In DeKalb, carriers average six to eight miles of walking each day and about five to six miles of driving, Myers said. The main purpose of vehicles on DeKalb's 25 city routes is not getting from place to place, but to store and “haul the mail.” On rural routes, mail is usually delivered by vehicle to serve less dense populations. In Cortland, for example, there are three rural routes and no walking routes, Postmaster Cindy Clark said. Genoa's routes are about evenly split between driving and walking routes, Postmaster Sue Loy said. But each post office operates based on the community's individual needs. “It's comparing apples to oranges because it depends on the type of delivery that's needed,” Loy said. The longest rural delivery route is in Fordville, N.D., where mail travels 175 miles to its destination. When adding more walking routes isn't feasible, post offices have turned to using other sources of energy. Along with having the largest vehicle fleet, the Postal Service has the world's largest fleet of alternative-fuel vehicles - about 36,000 of the 220,000 mail trucks use ethanol, compressed natural gas, liquid propane gas, electricity and biodiesel, Ratliff said. And the northern Illinois district, which includes post offices in DeKalb County, is leading the way in ethanol-fueled vehicles, Ratliff said. “We grow a lot of corn in the Midwest, and have taken advantage of the natural resources to reduce fuel emissions,” he said. For Cochrane, a good pair of Reeboks and exercise are substituting motor fuel costs. “I change shoes every two to three months. I can always tell when a pair goes bad because my legs ache at night,” he said. But he enjoys the exercise. “The day definitely goes faster when you're walking I think,” he said.