Citation

Wellman M, Miller S, Gray S, Zabransky J. Transp. Res. Circular 2008; (E-C126): 457-468.

Copyright

(Copyright © 2008, U.S. National Academy of Sciences Transportation Research Board)

DOI

unavailable

PMID

unavailable

Abstract

Snow, sleet, freezing rain, and rain are all common occurrences throughout the northeastern United States. These hazardous weather conditions can paralyze communities statewide. Reductions in traffic volume during these hazardous events can be used to quantify the number of people affected by a particular winter storm and provide a measure of how people perceive the severity of individual winter storms. Traffic counts were provided by the New Hampshire Department of Transportation for 15 locations across the state. These counts were then correlated with nearby weather observations, provided by the National Climatic Data Center and Plymouth State University’s online database. There were 51 storm events between November 1999 and March 2004. The reductions in traffic volume were calculated hourly and by day and compared with individual storm characteristics. The hourly reductions were compared to temperature, dewpoint, relative humidity, wind speed, wind direction, wind gusts, pressure, sky cover, visibility, precipitation type, and precipitation intensity. In addition the daily reductions were compared to snowfall amounts. A statewide average hourly reduction in traffic volume of 22.2% was found for all winter storms. Reductions in traffic volume were found to be most related to storm characteristics related to storm intensity. Storm hours with a northeast wind component were more likely to have the greatest reductions in traffic volume. Likewise, the intensity of snowfall on average across the state doubled the reductions in traffic volume. Reductions in traffic volume also held a strong relationship with visibility: the lower the visibility the greater the reductions in traffic volume. Hourly reductions were also closely correlated to diurnal pattern. The greatest reductions in traffic volume occurred after the evening commute; however, the greatest reductions in vehicles occurred during the evening commute. The comparisons between storm total snowfall and average storm reduction in traffic volume proved to be the most significant relationships. Storm average reductions were found to be related to storm total snowfall. However, they are most related to locations with the greatest average daily traffic volume. In addition, a direct relationship was found between the statewide storm average reductions and the statewide storm total snowfall, and an even stronger relationship with statewide average snowfall amounts greater than 5 in.