Aspects of traffic control devices.

This report contains the following reports: 1. Volume warrants for left-turn storage lanes at unsignalized grade intersections, M.D. Harmelink, p. 1-18 The derivation is described of volume warrants and design charts for left-turn storage lanes at unsignalized grade intersections on four-lane and two-lane highways. The design charts are based on a theoretical analysis and on a series of field studies of traffic behavior at intersections. The analysis is based on a queueing model in which arrival and service times are assumed to follow a negative exponential distribution. The arrival rates are determined by the volumes of left-turning, through or advancing and opposing traffic, and by the time interval required by the vehicle to clear the advancing lane. Service rates are determined by volume of opposing traffic, and by the time interval required to make a left turn maneuver. A left-turn storage lane is warranted by traffic volumes when the ratio of arrival rate to service rate exceeds a specified value, which varies with type of highway and vehicle speed. The required storage length of the lane may also be determined. Field studies were conducted of traffic behavior at seven unsignalized ontario intersections. Questionnaires on suitability or chart recommendations filled out by highway department regional traffic engineers at 80 ontario intersections indicated general agreement. 2. A practical computer program for designing traffic signal - system timing plans, Robert L. Bleyl, p. 19-33 This paper discusses the elements, techniques, and characteristics of a practical computer program developed for designing progressive traffic-signal-system timing plans. The elements discussed include directional travel distance variations, directional and sectional speed differences, band widths, offsets, cycle lengths, progressive speeds, and splits. The computer program, written in fortran iv programming language, converts all speed and distance units to travel time units. The timing plan resulting in the greatest efficiencies is then determined from a time-travel time diagram. The program favors the directional band widths in proportion to the desired relative band widths and prints a series of tables which indicate, from the ranges specified for the numerous variable elements, the optimum timing plan. /author/. 3. Use of a computer and vehicle loop detectors to measure queues and delays at signalised intersections, A. Christensen, p. 34-53 A computer program has been developed to obtain the traffic parameters of volume, speed, space headway, density and time headway from the pulses coming from vehicle loop detectors placed near an intersection. By finding the relations between time headway and queue length and time headway and delay, it is shown how the computer program can be used to find queue length and delay at signalized intersections. For the intersection studied, vehicle arrivals at the approaches were random, i.e., there was no platoon structure remaining after passage from the previous intersections. Graphs are shown of plots of delay vs volume, and of queue length vs volume. A means for correcting the counts lost is also developed. /author/. 4. The effects of street geometric and signalization on travel time and their relationships to traffic operations evaluation, J.F. Torres, p. 54-75 The effect of street geometrics and signalization are discussed in terms of travel time, which is defined as the time of travel through a street section averaged overall drivers and all specified time periods within a prescribed class. This is the key bactor in the evaluation of traffic operations. Travel time is shown to be significantly and reliably related to volume, given specific street section characteristics. An extensive sample of urban arterial street field survey data collected through a collaborative effort of state and local agencies, is employed to study the dependence of the travel time-volume relationship to the geometrics and traffic control factors. The principal variance-producing factors in the study sample are identified. A major result of the study is the determination of a set of general prediction curves by means of which the travel time-volume relationship can be estimated from knowledge of the characteristics of given specific streets. The application of the travel time results to the evaluation of traffic operations is indicated. /author/.