Establishing the validity of cycle path capacity assumptions in the Highway Capacity Manual
Authored by Chris Osowski, Ben Waterson
Date Published: 2017
DOI: 10.1080/15568318.2016.1266424
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Abstract
Cycle mode share increase is widely desired, but highway design
practitioners lack the numerical tools to deliver infrastructure,
instead relying on design standards and intuition, with little
literature basis. As a case in point, the US Highway Capacity Manual
(which is well used internationally) has developed levels of service for
cycle infrastructure that are, at their core, based on an assumption of
noninteraction between multiple cyclists. This paper uses a modified
implementation of the Social Force Model to test the validity of this
assumption. Necessary changes such as the consideration of acceleration
characteristics and minimum maintainable speed are included. The
resulting model produces valid outcomes in keeping with established
traffic flow properties, reflecting three-phase traffic flow theory and
the ability for the stochastic elements in traffic flow to cause flow
breakdown. The developed simulation indicates that there is a
fundamental difference in outcome if cyclists are assumed to have a
fixed speed versus one they can change given their surroundings. This
difference in outcomes is found to exist within the range of literature
design flow capacities for bicycle infrastructure and also yields
emergent outcomes that align closely with those known behaviors of
highway vehicles, which intuitively transfer to cyclists. These findings
reinforce the standing need for large-scale empirical studies to
determine the basic numerical and behavioral parameters for cyclists,
upon which all design ultimately rests.
Tags
Agent-based modelling
Simulation
behavior
Design
Dynamics
Traffic flow
Social force model
Bicycles
Cycle infrastructure