Quantification of Weather Influences on Freeway Bottlenecks

Weather is a major source of non-recurring delay on freeways within the United States.  How weather affects areas of daily recurring delay, particularly freeway bottlenecks, has not been thoroughly researched.  A type of freeway bottleneck in the form of a lane drop was studied across two winters at a site of daily recurring congestion.  This bottleneck was located in Pittsburg, California.  Queue discharge flow was compared between rainy days and clear days either one week before or after the rainy event.  Discharge flows during rainy events dropped by an average of 11% and this difference was significant to the 95% confidence level.  Conclusions could not be made on volume changes to individual lanes during rainy events.  With future examination of other bottleneck locations and types, analysts will be able to better predict trip times and agencies will gain knowledge for prioritizing operational improvements.