2011 Indiana Interstate Mobility Report—Summary Version

The 2011 Mobility Report—Summary Version introduces the use of crowd sourced probe data collected from vehicles and mobile devices to quantify the location and duration of congestion on Indiana interstates. The report presents a detailed case study of the I-65 corridor, as well as examples of travel time reliability information for sections of Interstates 65, 70, and 94. Summary monthly mobility statistics for all 943 centerline miles of Indiana Interstates 64, 65, 69, 70, 74, 94, and 465 are tabulated in a graphical format to facilitate comparison of mobility along those corridors

Leveraging High Resolution Signalized Intersection Data to Characterize Discharge Headway Distributions and Saturation Flow Rate Reliability

As highway systems become more congested, it becomes increasingly important to understand the reliability with which we can estimate important performance measures such as volume to capacity ratios, particularly as we move toward leveraging field infrastructure to obtain real-time performance measures. In 1947, Greenshields wrote a paper that characterized “green time consumed” by “car-in-line-number” that ultimately was called headway. Average headway is one of principles used by the highway capacity manual to estimate saturation flow rate at signalized intersections. However, the current analytical techniques calculate a deterministic value for saturation flow rate that does not consider the stochastic variation of saturation flow rate. This paper reviews techniques used to estimate saturation flow rate, and proposes enhanced calculation methods to group saturation flow rate estimates by queue length. Grouping saturation flow rate estimates by queue length provides a convenient framework to evaluate saturation flow rate reliability. The inter-quartile range (25% - 75%) of saturation flow rates was calculated to be 1000vph based on Greenshields’ calculation techniques. Using the proposed enhanced calculation characterizing saturation flow rate, the inter-quartile range of saturation flow rate was shown to decrease from approximately 400 vph with 5 cars in a queue to 300 vph with 10 cars in queue. Because saturation flow rate is a fundamental input to volume-to-capacity performance measures, characterizing the stochastic variation of saturation flow rates provides a basic input for assessing how reliably one can estimate important performance measures such as volume-to-capacity ratios, as well as other performance measures that build upon volume-to-capacity ratios

2011 Indiana Interstate Mobility Report—Full Version

The 2011 Mobility Report—Full Version introduces the use of crowd sourced probe data collected from vehicles and mobile devices to quantify the location and duration of congestion on Indiana interstates. The report presents a detailed case study presented of the I-65 corridor, as well as examples of travel time reliability information for sections of Interstates 65, 70, and 94. Summary monthly mobility statistics for all 943 centerline miles of Indiana Interstates 64, 65, 69, 70, 74, 94, and 465 are tabulated in a graphical format to facilitate comparison of mobility along those corridors. The report contains three appendices. Appendix A details the location of congestion pockets on each corridor. Appendix B provides quantitative summary of congestion for each interstate by month and direction. Appendix C provides travel time reliability statistics along three corridors in northern Indiana, twelve corridors in central Indiana, and four corridors in southern Indiana

Characterizing Reliability of Manual Intersection Turning Movement Counts Using Modern Data Collection Technology

Collecting intersection turning movement counts at intersections is an essential data collection task for many types of traffic engineering studies. On a daily basis, consulting firms and agencies collect turning movement counts that are used for preparing traffic impact studies, determining design hours for road improvements, and the retiming of traffic signals. Although there is a substantial body of literature on the stochastic nature of traffic volumes and how they vary by time, day of week, and season, the literature is quite sparse on how accurately turning movement counts can be collected at signalized intersections. The objective of this paper is to characterize the reliability of manual intersection turning movement counts performed with modern data collection technology. Live intersection turning movement counts were performed on three days for three hours to characterize the range and reliability of percent errors. Every user, regardless of interface or device, improved from the first day to the second day, and all but one improved again between the second and third day. There was no clear superior data collection technology, but with the emerging ubiquitous of smart phones and tablets, the cost –benefit of these devices has the potential to change the manual counting techniques of the future. Traffic counter software running on smart phones or consumer electronic devices has the benefit of being affordable and perhaps more convenient as an electronic counting device (ECD)