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4Introduction 1.1 Introduction The 2012 edition of the American Association of State High- way and Transportation Officialsâ Guide for the Development of Bicycle Facilities (AASHTO, 2012), often referred to as the Bike Guide, defines a bicycle lane as âa portion of a roadway that has been designated for preferential or exclusive use by bicyclists by pavement markings and, if used, signs. It is intended for one- way travel, usually in the same direction as the adjacent traf- fic lane, unless designed as a contra-flow lane.â The AASHTO Bike Guide provides general guidance on appropriate bicycle lane widths. The Bike Guide states that, in most situations, the recommended width for bike lanes is 5 ft, but in several cir- cumstances, wider bicycle lane widths may be desirable, and in several cases a 4-ft-wide bike lane can be used. Some transportation agencies use the guidance in the AASHTO Bike Guide to determine appropriate bicycle lane widths, while others have developed their own policies. Whether at the national, state, or local level, the guidelines that have been developed for bicycle lane widths provide only general guidance on how bicycle lane widths should vary based on the conditions of the roadway. Thus, there is a need to conduct scientifically based research to develop more specific guid- ance on bicycle lane widths for various roadway conditions. 1.2 Research Objective and Scope The objective of this research was to develop a set of rec- ommendations for bicycle lane widths for various roadway and traffic characteristics. The focus was on developing guidance for bicycle lane widths for roadways in urban and suburban areas since these areas are where bicycle lanes are most often considered and implemented. The overall guiding principle of this research was to provide guidance on how wide the bicycle lane should be in cases where the decision to include a bicycle lane has been made. The conclusions and research suggestions were drawn primarily from the research results of this study, while taking into consideration results from previous research. This research did not compare differences in bicyclist and motorist behaviors on roadways with bicycle lanes versus roadways with shared-lane markings. Therefore, this research does not provide specific guidance on the type of roadway and traffic characteristics where providing bicycle lanes may be preferred or not preferred compared to providing shared- lane markings, except when the conditions are so constrained that it is recommended bike lanes not be marked. On several roadways where on-street parking was prohib- ited, data were collected to compare differences in bicyclist and motorist behaviors on roadways with a wide curb lane versus roadways with a bicycle lane. Thus, on roadways where on-street parking is prohibited, this research provides general guidance on the differences in bicyclist and motorist behav- iors on roadways with a wide curb lane versus roadways with a bicycle lane. 1.3 Overview of Research Methodology In Phase I of this study, the research team conducted a literature review and state-of-practice review on bicycle lane widths. The results of this review are summarized in Section 2. In Phase II, observational field studies were conducted. At several locations, temporary pavement markings were installed to delineate bicycle lanes of varying widths, and the lateral positioning of both bicyclists and motorists was measured and used as surrogates to evaluate the safety effects of the allocation of roadway width between parking lanes, bike lanes, buffered spaces, and motor vehicle travel lanes. The data collection sites included three midblock locations with on-street parking and two midblock locations where on-street parking was prohib- ited. The bicycle lane widths evaluated ranged from 3.5 to 6 ft. A supplemental grade study was also performed to evaluate S E C T I O N 1
5 lateral movement of bicyclists while pedaling on a moderate upgrade. 1.4 Outline of Report This final report documents the entire research effort, with the remainder of the document organized as follows: ⢠Section 2 summarizes the findings of the literature and state-of-practice review. ⢠Section 3 describes the observational field studies con- ducted to evaluate the effects of varying lane widths on bicyclistsâ and motoristsâ lateral positioning. ⢠Section 4 describes the supplemental grade study performed to evaluate lateral movement of bicyclists while pedaling on upgrades. ⢠Section 5 presents design guidance for bicycle lane widths, taking into consideration various roadway and traffic characteristics. ⢠Section 6 provides conclusions and suggestions for next steps. For practitioners most interested in the design guidance developed as a result of this research, Section 5 will be of most interest.
