WAC 204-41-080
WAC 204-41-080. Commercially recognized delivery vehicles
Operators of commercially recognized delivery vehicles making frequent stops when traveling wholly within the limits of a town of less than ten thousand population, traveling less than one mile between stops on roads with a posted speed limit not greater than thirty-five miles per hour, while actually on a designated delivery route are not required to wear a seat belt system. Seat belt use is required when traveling to and from the designated route.