Fitting time headway and speed distributions for bicycles on separate bicycle lanes

The increasing sensitivity of policy-makers towards more sustainable and healthy transport is leading to increased interest in cycling, especially in urban areas. However, at the same time, recent studies in Europe, US and other countries have stressed the fact that cyclist fatalities are still alarmingly frequent, and lead researchers to want improved knowledge about bicycle traffic flow theory and modeling. The challenge is to make available robust analysis methods and models for building effective and safe infrastructures, for increased cycling mobility combined with positive effects on transport and social systems. This work presents the application of a procedure for fitting bicycle time headways and bicycle speed distributions from traffic data collected along bike tracks. The general frame of the procedure, together with functional components and their mutual interactions, are reported here. The effects of flow rate in both directions (analyzed and opposite) on time headway and vehicle speed distributions were examined. The possibility of associating the probability density functions of bicycle time headways and speeds in various cycling traffic conditions is a significant and interesting advance with respect to previous works. The procedure was applied to cross-sections belonging to the cycling network of the city of Bologna (Italy). The analysis compared a set of headway and speed distribution models, highlighting their goodness-of-fit with reference to empirical distributions.