Travel time based mobility measures have been increasingly used in highway performance analyses. Among them, Travel Time Index (TTI), Planning Time Index (PTI), percentage of travel under congestion (PTC), and buffer index (BI)have been identified as measures of particular interests in Kentucky. The objectives of this study are: (1) Calculate TTI, PTI, PTC, and BI for freeways within the TRIMARC coverage; and (2) Explore potential correlation between the reliability measures and incident characteristics (e.g., number of incidents, duration, severity, etc.). These analyses were performed for the years 2006-8 for each monitored segment and freeway corridor as well as for the entire freeway system.

Report Date


Report Number


Digital Object Identifier



The contents of this report reflect the views of the author who is responsible for the facts and accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the University of Kentucky, the Kentucky Transportation Cabinet, nor the Federal Highway Administration. This report does not constitute a standard, specification, or regulation. This inclusion of manufacturer names and trade names are for identification purposes and are not to be considered as endorsements.