00626845

Component

http://onlinepubs.trb.org...trr/1992/1365/1365-007.pdf

https://scholar.google.co...+Lin&publication_year=1992

For capacity analysis of signalized intersections, a left-turn adjustment factor is used in the 1985 Highway Capacity Manual (HCM) to account for the effect of left turns on saturation flow rates. When shared permissive left-turn lanes are the subject of analysis, the HCM uses a theoretical model to determine the related adjustment factors. Questions concerning the reliability of this model have been raised, and a recent study sponsored by the Federal Highway Administration has suggested that the HCM model be replaced by a set of new models. The new models, however, have serious flaws. An improved model that provides logical explanations of the causal relationships between the left-turn adjustment factor and its contributing factors is described. The contributing factors include opposing flow rate, number of opposing lanes, flow rate in the lane adjacent to the shared lane, proportion of left turns in the shared lane, proportion of left turns in opposing flow, proportion of opposing vehicles arriving in red interval, cycle length, green interval, and change interval. A numerical example is given to illustrate the applications of the improved model.

This paper appears in Transportation Research Record No. 1365, Highway Capacity and Traffic Flow. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved

01404949

English

p. 62-70

1992

Transportation Research Record

0309054044

Figures (7) ; References (4) ; Tables (3)

Adjustment factors; Highway capacity; Left turns; Saturation flow; Signalized intersections; Traffic simulation

Highway Capacity Manual

Contributing factors

Highways; Operations and Traffic Management; I71: Traffic Theory

TRIS, TRB

Feb 17 1993 12:00AM

• CAPACITY OF TWO-LANE, TWO-WAY RURAL HIGHWAYS: THE NEW APPROACH
• CAR-FOLLOWING MODEL BASED ON FUZZY INFERENCE SYSTEM
• DEVELOPMENT OF AN IMPROVED HIGH-ORDER CONTINUUM TRAFFIC FLOW MODEL
• EMPIRICAL METHOD TO ESTIMATE THE CAPACITY AND DELAY OF THE MINOR STREET APPROACH OF A TWO-WAY STOP-CONTROLLED INTERSECTION
• IMPLEMENTING TRAVEL FORECASTING WITH TRAFFIC OPERATIONAL STRATEGIES
• INVESTIGATION OF THE IMPACTS OF RAMP METERING ON TRAFFIC FLOW WITH AND WITHOUT DIVERSION
• MODELING QUEUED DRIVER BEHAVIOR AT SIGNALIZED JUNCTIONS
• NETWORK PROGRAMMING TO DERIVE TURNING MOVEMENTS FROM LINK FLOWS
• OVERSATURATION DELAY ESTIMATES WITH CONSIDERATION OF PEAKING
• POTENTIAL ACCURACY OF A PLANNING APPLICATION FOR THE HCM SIGNALIZED INTERSECTION OPERATIONAL PROCEDURE
• SIGNAL TIMING DETERMINATION USING GENETIC ALGORITHMS
• STATISTICAL PROPERTIES OF VEHICLE TIME HEADWAYS
• STUDY OF HEADWAY AND LOST TIME AT SINGLE-POINT URBAN INTERCHANGES
• SYNTHESIS OF RECENT WORK ON THE NATURE OF SPEED-FLOW AND FLOW-OCCUPANCY (OR DENSITY) RELATIONSHIPS ON FREEWAYS
• VARIANCE REDUCTION APPLIED TO URBAN NETWORK TRAFFIC SIMULATION (WITH DISCUSSION AND CLOSURE)