Measurement of travel time reliability of road transportation using GPS data: A freight fluidity approach

Travel time reliability is one of the most important assets when it comes to designing and assessing freight fluidity of transportation systems. Guaranteeing reliable delivery times is, according to different international studies, a strategic competitive advantage. Nonetheless, emerging countries such as Mexico, do not currently count with specific indicators to measure travel time reliability from a freight fluidity approach. As such, there is no clear measurement of the impact and propagation of the variability of transit times throughout the supply chains. Since road transportation is the main mean of transportation in emerging countries, the aim of this paper is to present the analysis carried out to measure the travel time reliability thanks to different methodologies based on freight data collection using GPS (Global Positioning System), as a key element to assess freight fluidity in freight transportation corridors. The analysis measured items such as: (i) percentiles of travel time; (ii) planning time index; (iii) buffer time index; (iv) skew and range of travel. Different probability distributions were analysed and the distribution of travel time data was determined through statistical hypothesis test. The conclusion was that distributions with upper tails longer than usual fit better to the collected data. Evidences of mixture distributions in the travel time data were also found. Finally, the paper also presents useful conclusions to develop future research as well as to improve practices for decision makers.