December 27


The Top 9 Changes in the New 6th Edition of the Highway Capacity Manual

By Mike Spack

December 27, 2016

Highway Capacity Manual 6th Edition, traffic corner, Webinar

The Highway Capacity Manual 2010 (jargon alert: HCM) has been converted to the 6th Edition of the Highway Capacity Manual here at the close of 2016.  The HCM 2010 was a historic overhaul while the new 6th Edition is more of an update.

We did a live Traffic Corner webinar on December 6th covering the significant changes that every traffic engineer should know about.  You can watch a recording below.  Covered in the half hour webinar are what I think are the Top 9 Changes in the HCM:

  1. More Capacity at Roundabouts
  2. Addition of Alternative Intersections
  3. Addition of Free Right Turn Lanes at Signalized Intersections
  4. Addition of Auxiliary Through Lanes at Intersections
  5. Addition of Diverging Diamonds
  6. Addition of Work Zone Capacity Analysis
  7. Addition of Managed Lanes
  8. Adding Adjustment Factors for Weather & Incidents
  9. Tweaking Level of Service A threshold for Urban Streets

  • I’m a little late, but thanks for the great webinar.

    Is it typical practice to factor your traffic volumes for design and operational analysis to the highest month of the year (depending on time of data collection) to account for 30 HV (as the 30 HV usually occurs during the highest month of the year)? Or should you just view historic trends for the 30 HV and collect data as close as possible to that time?

    Thanks again for all your great work in moving the profession forward!

  • Hi Mike – The industry generally assumes the 30 HV is represented by a typical weekday peak hour. If the area has unusual seasonal peaks (i.e. a summer resort town), you’d want to look at a peak hour from that peak month. Mike

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    Mike Spack

    My mission is to help traffic engineers, transportation planners, and other transportation professionals improve our world.

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