Statistical investigations of statutory holiday effects on traffic volumes

Traffic volume fluctuates from time to time and from location to location, with significant variations in demand as a result. The increases in travel during statutory holiday periods are substantial, and some critical traffic problems have been reported. An understanding of this substantial variation in the volume of traffic can assist transportation agencies in developing practical countermeasures in aspects such as traffic control plans, signal timing, safety programs, traffic volume monitoring, and prediction. The literature on holiday traffic is limited, and no effort has been made to examine statistically the significance of changes in traffic volume due to holiday effects. With the past 20 years of data collected by permanent traffic counters on highways in Alberta, Canada, holiday effects on road traffic are shown graphically. Then, the nonparametric Wilcoxon matched pair test is used to test the variation characteristics of normal flow, the Friedman method is applied to investigate the holiday effects on weekly and daily traffic, and the hourly volume pattern changes are examined by a combination of chi(2) and binomial tests. The test results reveal that holidays substantially contribute to the variability of traffic. The weekly volume variations during holiday periods are significant in many cases, holiday effects on daily and hourly traffic are evident, and the directional holiday traffic peaking features are strong. Meanwhile, general identifications of the affected holidays for different types of roads are provided. Potential implications of these findings are discussed.