Citation

Normann OK. Highw. Res. Board bull. 1962; 352: 55-99.

Copyright

(Copyright © 1962, National Research Council (U.S.A.), Highway Research Board)

DOI

unavailable

PMID

unavailable

Abstract

The following variables were obtained and analyzed in this study: Load factor, peak-hour factor, and vehicles per hour of green. The principle objective of studying traffic flow at intersections is to improve the efficiency of traffic movement, particularly with respect to reducing delays and traffic accidents. Relations are investigated between intersection capacity, delay and load factors. The load factor is a means for studying intersection capacity at or near capacity volumes. Relations are analyzed between peak- hour factor and approach capacities. The following four principal variables were found to affect the hourly flow of traffic through intersections: (1) peak-hour factor, (2) load factor, (3) the approach width at the intersection, and (4) size of the city. The effect on capacity of these four primary variables was determined by a series of successive approximations. The effect of the peak-hour factor on intersection capacity was determined by holding the load factor constant during the peak hour. In all cases, the load factor was shown to have a very marked effect on the traffic flow. Advantages and disadvantages are discussed of length of green phase. Effects are examined of the type of street by system, on-street parking, location within a city, effect of rain on intersection capacities, effect of local buses and other factors. The use is described of load factor ratios in determining efficiency of signal operation. The most efficient movement of traffic and the least total delay occurs at an intersection when the two approaches carrying the major cross-movements are loaded to their same relative capacities. It is concluded that the improvement of efficiency of traffic movement at intersections is one of the more important urban transportation problems.