Analysis of Bus Travel Time Reliability Using GPS Data

Due to the considerable effects of bus travel time reliability on the efficiency of the bus system and its quality of service, in this paper, we attempt to analyses the travel time reliability using a GPS travel time data set of two bus routes in Tehran, Iran. To this end, we firstly review some of travel time reliability measures introduced in the literature. We then explore the variability of these measures in the course of a day. Our results indicate that the variability of travel time in the afternoon peak hours is more that in the morning peak hours. We also examine the distribution of travel time for different time intervals of the day. Based on empirical data, it can be concluded that the distribution of travel time is not only wide but also rightly skewed. Results also show that Burr, Log-logistic and Log-normal distributions are superior to other probability distributions in terms of fitting accuracy. Furthermore, travel time can be more precisely fitted using mixture probability distributions.