This report documents the second part of the FHWA research study involving analysis of the microscopic impacts of adverse weather on traffic flow, but is a third phase of the research effort on the impacts of weather on traffic flow. The first phase of FHWA research involved macroscopic analysis, which focused on the impacts of adverse weather on aggregate traffic flow. The second phase of research analysed the impacts of adverse weather on microscopic traffic behaviour. This report documents the results of three research efforts (1) The impacts of icy roadway conditions on driver behaviour at a microscopic level, using field-measured car-following data,; (2) An investigation of the influence of weather precipitation and roadway surface condition on left-turn gap-acceptance behaviour using traffic and weather data collected during the winter of 2009-2010 at a signalised intersection in Blacksburg, Virginia; and (3)The development and demonstration of methodologies for the use of weather-related adjustment factors in microsimulation models, including general approaches to construct simulation models accounting for the impact of precipitation. For the third effort, the general approach was applied to the calibration of the VISSIM and INTEGRATION simulation software. (Author/publisher)
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