UPS hires bicyclists to help with holiday deliveries - it's more cost-effective to hire bicyclists than extra delivery trucks, and
saves an average of 17 gallons of fuel per day (compared to one truck).
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I found this info after my wife called and told me she received packages from a UPS delivery guy on a bike. Our town is only about 10 miles across, so you can access most areas pretty quickly. Still, getting from one side of town to the other loaded with packages might be tricky without continuous bike lanes and some rather narrow roads.