Just because the name listed on the street signs is the route number does not necessarily mean that Piestewa Freeway should be tagged name=AZ 51(also all the street signs say SR 51 not AZ 51). The City of Phoenix puts route numbers on freeway street signs instead of the name as it is more helpful for navigation on the ground. The name of the freeway is still Piestewa Freeway regardless of the names on the street sign. The route is tagged in the ref tag.