June 29


Calculating the 85th Percentile Speed

By Mike Spack

June 29, 2017

85th Percentile, speed limit, Traffic Corner Tuesday, Traffic Engineering

By Jonah Finkelstein, EIT

We recently completed a Traffic Corner Tuesday where we discussed the importance of the 85th percentile speed and what it is used for in the world of traffic engineering.


Once the webinar was finished we received multiple messages about how people enjoyed the information on the importance of the 85th percentile speed, however, we did not discuss how the 85th percentile speed is determined on a roadway. Well… ladies and gentlemen, the wait is finally over. Here you can find a quick summary of the uses of the 85th percentile speeds, why it is important, and most importantly of all how to calculate the 85th percentile speed on a roadway using collected speed data.

Want more information on 85th percentile speeds? Check out these resources:


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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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