 AASHTO suggests that transportation authorities of the United States remove other types of special routes and/or replace such obsolete designations with another type of route.Some old alignments of routes may also be informally known as special routes (despite some that do not intersect the parent route).These older alignments may be given street names like "Old U.S. Highway 52", or in some rare cases, be signed with route shields attached to "Old" or "Historic" sign plates (such as decommissioned sections of former U.S. Route 66 that are still driveable).