Highway Capacity Manual

The Highway Capacity Manual (HCM) is a publication of the Transportation Research Board (TRB) of the National Academies of Sciences, Engineering, and Medicine in the United States.

The most-recent version, the Highway Capacity Manual, Seventh Edition: A Guide for Multimodal Mobility Analysis was released in January 2022.

It was the result of a collaborative effort between the Transportation Research Board (TRB) and the Bureau of Public Roads, the predecessor to the Federal Highway Administration.

[5][6] The final version, published as the Highway Capacity Manual, Sixth Edition: A Guide for Multimodal Mobility Analysis, or HCM 2016, or HCM6, was released in October 2016 and is available from TRB.

[2] The sixth edition incorporates the latest research on highway capacity, quality of service, active traffic and demand management, and travel time reliability.