The purpose, need for and effects of urban beltways is a topic of much discussion. Surprisingly little research has been conducted on beltways, through nearly every major city in the United states has built one or more since 1960. Early beltways were
constructed to bypass central business districts (CBDs) and the congestion on the radial highways connecting to CBDs. The purpose was to reduce travel time and congestion. As the economy and population of areas grew, the beltways were used as routes between suburbs, becoming a 'which came first' question. One study found that "contrary to popular belief, the geographic area, population and employment of no-belt or partial belt cities have increased faster than in (cities with beltways.)" In 1950, North Carolina adopted the Radial-Loop Thoroughfare system and has used it as guiding principle in urban planning. Urban loops provide for lateral movement between suburban areas where
new development is occurring and also divert traffic from local roads and streets. The alternative to a complete beltway system in the Denver metro area is to put an ever increasing number of cars on I-25, I-70, and on local roads.  The goal of the Jefferson Parkway is to keep regional traffic off of local streets by providing a safe, convenient and efficient alternative.