The increase of cyclist presence in urban areas and of the number of cyclist accidents on roads lead researchers to explore the in-traffic visual behavior and hazard perception of cyclists.In this study the actual cyclist gaze behavior while cycling on bicycle tracks-exclusive or shared with pedestrians is analyzed. The intent is to allow a better comprehension of those elements representing interferences, which can influence user's trip. Field tests were performed in the urban center of Bologna, Italy. 16 participants were asked to wear mobile eye tracking glasses and cycle along a defined route. From gaze data recorded by the mobile eye detector, we analyzed which visual information are detected. By applying fixations detection algorithm and then a frame-by-frame analysis we calculated the proportion of fixations-number and duration-across different areas of interest. Proportion of fixations and fixation time are assumed as a proxy of visual workload. Thus, the relative frequency of fixation has been used to rank those elements that draw cyclist attention.Three are the main outcomes: first, an equilibrium of attention location between the central (trajectory) and lateral parts of the visual scene can be assumed as the optimal cycling visual condition. This condition results compromised when the presence of pedestrians is high. Second, discontinuities of the path (like intersections and crosswalks) and the presence of pedestrians are the elements requiring more attention. Third, the absence of physical and visual separation between cyclists and pedestrians seems to lead to a lack of attention to these risk elements.These outcomes about cyclists' visual behavior allowed to recommend design measures to increase comfort and safety on shared-with pedestrian-cycling paths. Thus, suggestions are addressed in the conclusions.
Three are the main outcomes: first, an equilibrium of attention location between the central (trajectory) and lateral parts of the visual scene can be assumed as an optimal cycling visual condition. This condition is compromised when the presence of pedestrians is higher.
Second, discontinuities of the path (like intersections and crosswalks) and the presence of pedestrians seem to be the elements requiring more attention. On the exclusive cycling path, the majority of the fixations were spent watching the interruptions of the path with approximately the same frequency both in the central visual area (trajectory and end of the path) as out of this region. Third, the absence of physical and visual separation between cyclists and pedestrians seems to lead to a lack of attention to risky elements, such as intersections and crosswalks. If the presence of pedestrians increase, the time spent monitoring elements as conflicts and risk points is lower. Instead, a higher grade of separation between the two different classes of vulnerable users – cyclists and pedestrians – creates a benefit in terms of cyclist concentration on other elements, e.g. as intersections.
Other interesting observations about the adopted visual strategies: firstly, the other cyclists encountered drew the rider’s attention when they were within the target region, in front of the cyclist, rather than in a lateral position -in the OUT region. Instead, pedestrians are detected despite their position with respect to the rider. Probably a cyclist’s trajectory is perceived as more predictable and once the other cyclist has been identified in the target area he/she is not followed further with the gaze, in lateral regions. On the contrary, pedestrian movements are assumed to be more unpredictable in their trajectory and thus more alarming. Secondly, path discontinuities and motorized vehicles at intersections seem to be perceived as hazardous elements on which cyclists concentrate monitoring the central and final visual area of the path. Indeed, for this elements, significant statistical differences resulted only for fixations in the target area, to the end of the path.
The results of this research can address designers to consider different design strategies to increase the comfort and perceived safety of cycling lanes, especially, when it is not possible to realize new exclusive bicycle paths.
The findings of this work show that when the existent urban space and infrastructures are used, i.e. cycle path on sidewalks, specific design elements should be employed to increase the visual (physical) separation. It has been found that where the presence of pedestrians within the cycling space is more likely, relevant elements such as intersections are less observed -the relative frequency were almost two times lower. For this reason, the adoption of barriers or other physical elements to define cycling lane should be recommended also on sidewalks, not only on road. Indeed, circumstances where the road is used rather than adjacent bike lane on sidewalks are frequently verified. In this work it has been measured that a higher grade of separation between the two different classes of vulnerable users – cyclists and pedestrians – could lead to a benefit in terms of cyclist concentration on other elements. For this reasons, the practice of defining large, open, shared cycling/pedestrian space could not be the best strategy when bicycle paths and corridors have to be planned. Picket fences, light barriers, plant racks, arbors, or trees can be soft –and cheap- measures that can be easily adopted. As it has been showed path discontinuities and motorized vehicles at intersections, seem to be perceived as hazardous elements on which cyclists concentrate. The increase of visual separation and the consequent reduction of visual spread must be combined with a high and clear signaling of conflict points. It resulted that these elements were monitored in the central and final visual area of the path. Thus they should be consequently located: vertical signs should be evident and overhead (not in the middle of the bike lane) to let cyclist visualize them from a sufficient distance - without them to become obstacles.