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The Plus 15 or +15 Skyway network in Calgary, Alberta, Canada, is the world's most extensive pedestrian skywalk system, with a total length of 18 kilometres (11 miles) and 62 bridges. The system is so named because the skywalks are approximately 15 feet (approximately 4.5 metres) above street level. (Some Plus 15 skywalks are multi-level, with higher levels being referred to as +30s and +45s.)
The system was conceived and designed by architect Harold Hanen, who worked for the Calgary Planning Department from 1966 to 1969. This development earned him the 1970 Vincent Massey Award for Merit in Urban Planning.
Opening in 1970, the +15 network has expanded to include 59 enclosed bridges connecting dozens of downtown Calgary buildings. The central core of the system is a series of enclosed shopping centres, and the city's flagship department stores.
New developments were required to connect to the walkway system; in exchange for this, they were offered more floorspace (the "bonus density"). When not physically able to connect to nearby buildings, developers contribute to the "Plus 15 Fund", managed by the city, used to finance other missing connections.
Although there are currently[when?] no plans to remove bridges or to discontinue building new ones, the system has been subject to criticism in recent years. It has been identified with a decline in street life in the Downtown Commercial Core. Street life is instead concentrated on streets (such as Stephen Avenue) or in neighbourhoods where there are no bridges (such as Eau Claire and the Beltline). No conclusive evidence exists that similar cities without skywalk systems have greater downtown street life.
Future of the +15 system
In recent years, the city has begun to re-evaluate the system. Part of the goal of these studies was to find ways of addressing the problem of decreased daytime street life on some downtown streets. The possibility of limiting expansion has been raised to encourage more pedestrian street traffic. The +15 system bridges are integral with the buildings they serve. City planning by-laws presently confer tax credits to developers and building owners who connect new buildings to the existing system. This may change in the future, however, if the city begins to consider relaxing these bylaws. Presently, however, businesses and general public make extensive use of the +15 system—a system that has served to enhance the flow of human traffic. The +15 system has and will likely continue to provide both economic and climatic benefits now and in the future.
The +15 in popular culture
List of buildings connected
-  City of Calgary - Calgary's +15 Skywalk
- City of Calgary - Plus 15 System
- "+15 User Survey", a City of Calgary study published in 1998
- Plus 15 Network Map
- Interactive Plus 15 Application
- +15 Map with iPhone app
- +15 Ninja - Directions, Meetups & Directory