Citation

Johnson AN. Highw. Res. Board Proc. 1932; 1932.

Copyright

(Copyright © 1932, National Research Council (U.S.A.), Highway Research Board)

DOI

unavailable

PMID

unavailable

Abstract

A summary is presented of a research project to determine capacity of two, three and four lane roads. The influence of the proportionate amount of traffic in one direction is not marked on 2-lane roads until the fraction increases to 80% or more, when a greater volume of traffic is carried without congestion. The average working capacity for 2-lane roads is approximately 95 per 5-minute interval or 1000 per hour. Three-lane roads appear to operate to slightly better advantage when 70% of the traffic is in one direction. The average working capacity is approximately 180 per five-minute interval or 2000 per hour. Four-lane roads have an average working capacity of 290 vehicles per 5-minute interval. The addition of one lane to a 2-lane road increases its width 50% and its capacity 100%. Addition of two lanes increases the width by 100% and the capacity by 200%. However, this study relates to traffic capacity only and no consideration was given to the relative safety of the various lane designs under varying volumes of traffic.