Quantifying the role of disturbances and speeds on separated bicycle facilities

As cities aim to spur cycling, a key issue revolves around the location and quality of separated bicycle facilities. However, sometimes owing to impedances, these facilities fail to have the desired overall utility for cyclists. This study focuses on the role of non-stationary disturbances, i.e., the presence of users of other modes. The aim is to quantify the effects and frequencies of disturbances on offstreet bicycle facilities (from other cyclists and pedestrians) and compare them to disturbances (from motorized vehicles) while cycling in mixed traffic. Using three segments in Bologna, Italy, we measured the frequency, type, and speed reduction attributed to different types of disturbances. We analyzed speed and likelihood of events to calculate a weighted average of the cyclists’ speed for separated bicycling facilities and on the roadway. For two of the segments, weighted speed reductions were minimal. However, in a third segment—one with considerably more disturbances—speed reductions were considerable: 20 percent for the separated facility and 40 percent for the mixed traffic. When married with cycling use patterns along the facilities, the notable speed reductions point to a possible trade-off cyclists make in choosing between different routes. The results help quantify relationships between cyclists and non-stationary disturbances; they also caution transport officials about possible unintended outcomes for separated bicycle facilities.