The Highway Capacity Manual ― A Conceptual and Research History - Uninterrupted Flow

Since 1950, the Highway Capacity Manual has been a standard used in the

planning, design, analysis, and operation of virtually any highway traffic facility

in the United States. It has also been widely used abroad, and has spurred the

development of similar manuals in other countries.

The twin concepts of capacity and level of service have been developed

in the manual, and methodologies have been presented that allow highway

traffic facilities to be designed on a common basis, and allow for the analysis of

operational quality under various traffic demand scenarios. The manual also

addresses related pedestrian, bicycle, and transit issues.

This book details the fundamental development of the concepts of

capacity and level of service, and of the specific methodologies developed to

describe them over a wide range of facility types. The book is comprised of two

volumes. Volume 1 (this book) focuses on the development of basic principles,

and their application to uninterrupted flow facilities: freeways, multilane

highways, and two-lane highways. Weaving, merging, and diverging segments

on freeways and multilane highways are also discussed in detail. Volume 2

focuses on interrupted flow facilities: signalized and unsignalized intersections, urban streets and arterials. It is intended to help users of the manual understand how concepts,

approaches, and specific methodologies were developed, and to understand the

underlying principles that each embodies. It is also intended to act as a basic

reference for current and future researchers who will continue to develop new

and improved capacity analysis methodologies for many years to come.