Since the publication of the Highway Capacity Manual (HCM) 2010 edition, more than $4 million of funded research had been completed on a variety of topics touching every part of the HCM: travel time reliability analysis for freeways and urban streets, updated roundabout capacities, new alternative intersection and interchange forms, work zones, managed lanes, truck analysis, and planning and preliminary engineering applications. A major update to the entire HCM was needed to integrate each of these individual research efforts.


Kittelson led the project team that produced the HCM 6th Edition. A vital activity during the update process was distributing draft documents to a large number of reviewers, obtaining reviewer comments, and documenting how each comment was addressed, all of which was accomplished through a special password-protected website. Kittelson also coordinated with other researchers whose work was to be incorporated into the HCM, as well as with Transportation Research Board (TRB) publications staff to produce the final printed and online documents.

The Outcome

Improving the Essential Guide to Moving People and Goods

Cover, Highway Capacity Manual, 6th EditionThe HCM 6th Edition reflects the latest in capacity and quality of service analysis across a full spectrum of facility types. It retains the basic four-volume structure of the previous 2010 edition but includes restructured content to improve readability and consistency in presentation. Example problems and other new content were placed in the online-only Volume 4. The HCM is also now set up to be updated incrementally as new research is completed.



Fort Lauderdale






Transportation Research Board, National Academy of Sciences