Development of Daily Adjustment Factors for Bicycle Traffic

Abstract

Daily and monthly adjustment factors have traditionally been used to expand the estimation of daily traffic volumes into average monthly and average annual traffic. However, research efforts that are devoted to developing and evaluating these factors for nonmotorized traffic, especially for cycling, are currently rare. This is attributed mainly to the lack of extensive data that can enable reliable calibration and testing of such factors. This paper explores some issues related to the development and application of daily adjustment factors for bicycle traffic. Examples include the impact of grouping daily factors by weekday/weekend and developing weather-specific factors and factors for different road classes. The analysis made use of a large data set of 500 months of daily bicycle volume data that covered 74 links in the city of Vancouver, Canada, for the years 2010 and 2011. Monthly average daily cycling volumes were estimated using different sets of factors, and the estimation accuracy was assessed and compared. It was found that developing factors for each day of the week provided similar estimation errors to grouping the factors for weekdays and weekends. In general, the best estimation results of the monthly average cycling volumes were achieved when using daily factors that are disaggregated by weather conditions. The temporal transferability of the factors was also evaluated by applying the factors from 2010 and 2011 to data from 2009. Compared to the daily factors from 2011, it was shown that the factors from 2010 provided slightly better estimation accuracies of the monthly average of daily bicycle traffic for different months in 2009. This demonstrates the degradation in the reliability of the daily adjustment factors over time, which calls for an update of these factors every few years.