Stads- och trafikplaneringens paradigm : en studie av SCAFT 1968, dess förebilder och efterföljare
Swedish towns have been developed according to the planning guidelines issued by the National Road Administration and the National Board of Urban Planning in 1968; SCAFT 1968 Riktlinjer för stadsplanering med hänsyn till trafiksäkerhet (The SCAFT Guidelines 1968 Principles for urban planning with respect to road safety). The five principles for urban planning suggested are; Locating activities and functions, Separating different classes of traffic, Differentiation within each road network, Clearness, simplicity and uniformity as well as Neighbourhood units. These planning principles are shown to form the core of all urban planning principles, instructions and advice issued by Swedish authorities since then, no matter which political objectives the planning processes deal with.
This study begins with the strange circumstances that these five principles for urban planning, once issued to improve urban traffic safety, are still recommended and are recommended to achieve today's qualities. The explanation for these circumstances is investigated with the help of Kuhn's theory. The study uses two approaches; a reconstruction of the history of the planning principles and an analysis of the planning principles within the history of ideas. It is shown that the SCAFT guidelines form a paradigm.
It is found that the scientific evidence supporting the SCAFT planning principles are weak. Instead it is found that the 'modern city' concept of Le Corbusier, with roots in Garnier and Haussman among others, forms a strong source of inspiration not earlier questioned by the new problems politicians and planners have to deal with. When it is possible to use other models, planning principles and solutions with better results to solve these new problems, the use of the old planning principles creates anomalies:
Anomaly 1: Tree-like road networks compared to grid-like road networks create longer distances and therefore increased transport not the opposite.
Anomaly 2: Traffic regulations and 30 km/h zones require that main streets shall have the function of through traffic and pedestrians and cyclists demand to cross only local streets. The demands from pedestrians and cyclists are the opposite.
Anomaly 3: Car traffic through areas, neighbourhood units etc. should be prohibited by differentiation, but there are no distinct areas in a traditional town.
Anomaly 4: The SCAFT guidelines are based on the assumption that good traffic safety can be combined with high speed as long as the traffic environment gives a clear view, is simple and uniform. But with higher speed there is less time for correction and the consequences of errors and failures are more serious.
Although traffic regulation and 30 km/h zones do not fit into the SCAFT paradigm, these measures will form the basis for the safe renewal of urban transport.