In the mid-1980s, the route structure was changed to form the basis for the system operating today. Most routes were restructured so that they would stay on a single street rather than be based out of the downtown terminal. Routes that operated on multiple streets were also split (for example, route 22-Camelback Crosstown covers parts of today's route 50 and route 72). The route numbering system was simplified so that bus routes were numbered according to the block number of the street that they operated on. For example, route 50-Camelback is numbered because it runs mostly on Camelback Road, which is in the 5000 block. Because of the establishment of route numbers in the 80s and 90s, the express routes were renumbered to the 500-series, where they remain today. The second digit of the 500-series express routes denotes the region of the metropolitan area where the bus is traveling to (for example, the 510 series go to Scottsdale, the 530 series go to Mesa, and the 570 series go to the Northwest Valley). The evolution to a full "supergrid" structure continues today as route branches are either replaced with circulators or separated into new routes.