The main objective of this these was to assess the weather(i.e., snow or rain) impacts on traffic flow stability by comparing travel speeds from different weather conditions. For this, real traffic data were collected through a set of detectors installed at freeway, national highway, and urban arterial. Some of important findings were summarized as follows.
Results showed that weather impact on travel speeds was slightly different in term of highway classifications. It was found that urban arterial had higher speed difference than freeway and national highway under rainy and snowy weather conditions.
Analysis was also performed by assuming that the magnitude of weather impact might be changed from the levels of travel speed. Results showed that high weather impact was observed from low travel speed regions, indicating high travel time variations. In addition, high weather impact(i.e., travel time) was also observed when the roadway experienced congestion.
From these results, it was concluded that weather factor had a clear and meaningful impact on traffic flow. Therefore it was recommended that the weather factor should be considered during a roadway design or an operational strategy making process.
It was also recommended that a comprehensive further study was necessary to quantify the real effects by considering the characteristics of various traffic variables such as traffic volume, density, and speed.
