Prior to the formation of the RPTA, the bus route structure of Phoenix Transit System was quite different, both in terms of numbering and routes. Previously, the bus system was based on a "hub-and-spoke" structure with most routes starting from downtown Phoenix. These routes were split in half by Central Avenue, which most routes used to access downtown Phoenix. For example, the western half of Van Buren Street was served by route 3W, and the eastern half of Van Buren Street was served by route 3E. Most bus routes inherited a seemingly arbitrary, but chronologically assigned, system from their Phoenix Street Railway heritage (for example, route 0-Central was originally numbered route 5). Express routes were numbered in the 80s and 90s (for example: route 510 serving Scottsdale was originally numbered route 90, which is today assigned to route 90-Dunlap/Cave Creek).