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Urban transportation, Cyclists -- Case studies, Transportation -- Planning -- Oregon -- Portland


Higher bicycle mode share has been suggested as part of a solution to reduce the burden of congestion in urban areas. As strategies to promote bicycling are implemented, concerns have been raised by some road users and stakeholders citing simulation based traffic studies that indicate that an increase in the bicycle mode share generates major travel time delays via reduced vehicle speeds unless bicycle lanes are provided. The current research investigates the effects bicycles may have on motorized vehicle speeds on a variety of lower speed and volume urban roads without bicycle lanes. A detailed comparative analysis of passenger car speeds was performed using two vehicle scenarios: (i) a passenger car that was preceded by a bicycle, and (ii) a passenger car that was preceded by another passenger car. The mean and 85th percentile speeds of scenarios (i) and (ii) were analyzed using t-tests. Relationships between speed and gap times with oncoming (opposite direction) traffic were also investigated. The results indicate that at most sites (92%), bicycles do not reduce passenger car mean speeds by more than 1 mph. Speed reductions are not generally observed in local streets or facilities with adequate number of gaps in oncoming traffic for overtaking.


This is the author’s version of a work. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document.


Paper accepted for presentation at the 2021 TRB Annual Meeting (January 2021, 39 Washington DC) and potential publication in Transportation Research Record.

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