Transportation Infrastructure to Support Bicycling in Dense Urban Environments : Design and Operational Considerations for Bicycle Lanes in Proximity to Commercial Vehicle Loading Zones
While sophisticated plans have been adopted nationally and globally to increase bicycling’s share of daily commutes, safety concerns have negatively impacted targeted bicycling growth. Specifically, truck traffic plays a pivotal role in bicyclists’ perceptions of safety and comfort, because of the severe consequences of bicycle-truck collisions. Several types of engineering treatments, such as colored pavement markings and warning signs, can be applied to roadways to improve bicyclist safety and comfort in conflict areas. However, no endorsed sign or pavement marking directly addresses bicycle-truck conflicts in commercial vehicle loading zones (CVLZ).
This study investigated the influence of engineering treatments on bicyclist perceived level of comfort (PLOC) and analyzed their impact on bicyclist behavior during bicycle-truck conflicts.
First, an online survey was developed to probe people’s stated preferences for bicycling in urban areas. A total of 342 participants successfully completed the survey. Repeated-measures ANOVA results indicated that when bicycling on a conventionally striped bike lane, truck traffic had the most significant effect on bicyclist PLOC, decreasing it by more than 42%. Pavement markings were more effective than traffic signs at improving bicyclist PLOC, but no difference was observed between solid and dashed green lane markings. The results of cluster analysis indicated that the effect of gender and experience on bicyclist PLOC varied with different levels of traffic and engineering treatments. Women were more affected than men by the presence of a truck in the adjacent lane but they were also more prone to a considerable increase in PLOC values due to the implementation of engineering treatments. Structural Equation Modeling estimation results indicated that participants who said that they engaged in more frequent distracted bicycling reported lower levels of PLOC. On the other hand, those who felt that road users were more lawful and predictable, and had more bicycling experience reported higher levels of PLOC. Participants who were commuters, who made shorter trips, who had a higher frequency of bicycling, and who had more exposure to downtown bicycling also reported higher levels of PLOC. Findings showed that higher PLOC was significantly associated with the choice of a safe, rather than a risky response to the presence of a truck in the adjacent lane, suggesting that a way to improve bicyclist safety would be to build an environment that delivers an accurate perception of comfort for bicyclists.
Secondly, bicycling simulation experiments were developed to probe bicyclist’s revealed behavior during bicycle-truck conflicts. Experimental results from 48 participants showed that truck presence does have a significant effect on bicyclists’ performance, which varied based on the engineering and design treatments employed. Truck maneuvering had the greatest impact by decreasing the mean velocity and increasing the mean lateral position of bicyclists. It was also observed that when a truck was present in a CVLZ, solid green pavement markings caused bicyclists to have a lower velocity and lower divergence from the right-edge of the bike lane, and employment of a warning sign caused a larger departure from the right-edge of the bike lane.