Modelling bikeability; Space syntax based measures applied in examining speeds and flows of bicycling in Gothenburg

For numerous reasons related to energy demand, emissions, public health as well as liveable and attractive cities, a frequently stated aim in contemporary discussions on urban development is to increase amount and modal share of bicycling. In recent years, space syntax based methods have shown to be useful for providing informed premises for these discussions. Combining space syntax analyses with data on locations of residents, workplaces and destinations opens the door not only for predictive modelling of route choice preferences but also the potential amount of bicycling along routes. Building on previous research, the research presented in this paper develops space syntax based measures expected to capture bicycling and evaluates these measures by comparing the analyses with empirical data from studies carried out in cooperation with the City of Gothenburg. Among the variables considered essential for bicycling and included in our GIS model are: the slope and curvature of routes, the width and surface type of bicycle lanes and the kind and amount of traffic along the route. For modelling bicycling flow potentials, a measure termed Origin-Destination Betweenness (OD-betweenness) is used and tested, examining different combinations of variables and threshold distances. The empirical data consists of gate counts of bicycle traffic and detailed GPS-tracks mapping actual bicycling speeds of ca. 900 trips along a selection of bicycle routes. Using multiple regression analysis to model speed data, eight variables were found significant. In addition to slope and curvature of routes, the significant variables relate to proximity to traffic signals, degree of separation from pedestrians, density of entrances along the routes and quality of paving of the cycle lane. Concerning bicycling flow potentials, the most significant variables in the multiple regression model were: OD-betweenness within 5 km, segment angular integration within 10 km, density of residents and people at work (students included) within 1 km and network betweenness within 3km. Based on the results of the current project, a proposal for further research is to elaborate on the OD-betweenness analyses by including speeds and preferably traffic safety in the betweenness measure. By using time along segments instead of metric length for defining the analysis threshold (radius), it should be possible to have a new and improved generation of space syntax based accessibility analyses for bicycling studies. A working name for such a measure is “least impedance origin destination betweenness”.