Capacity and Level of Service at Unsignalized Intersections Final Report Volume 1 - Two-Way-Stop-Controlled Intersections (1996) / Chapter Skim
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Chapter Six. Capacity
Chapter Six. Capacity
Pages 65-74
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From page 65... ...
The Impedance effect of hither rank steams on the lower rank stream, the weighting factors used for calculating conflicting flow, the shared lane situation on He minor stream approach, and the platoon elect were considered during the model testing Special considerations were given to conditions such as the existence of a two-way lefc-turn CrWLT) lane on the major street, He existence of a raised median on the major streets or the existence of a downstream bottleneck.
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From page 66... ...
For example, if there is no exclusive right turn lane, only half of the major street right tum volume is counted as part of the total conflicting volume for the minor stream movements. At a multi-lane site, say a twolane by two-lane street, only half of the total Trough traffic from the left side is counted as part of the total conflicting Bow for the minor street right turn movement, and half of the total through traffic from the right side is counted as part of the total conflicting Bow for the minor street led turn movement At 4-leg intersections, only half of the through end right turn traffic on the opposing minor approachis counted as pert office total conflicting flow for the subject left turn movement.
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From page 67... ...
Because there were~insufficient data for testing the weighting factors for He through and right turn movements on the minor street opposing approach, this test concentrated on the weighting factors for the major street right turn movement, and the major street through movement at multi-lane sites. The opposing approach volumes make a relatively small contobudon to the total conflicting flow when compared to the Trough movements on the major street.
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From page 68... ...
Capacity Model Results Using HCM Weighting Factor and the Optimum Weighting Factor for Major Street Right Turn Movement Table 32. Regression and Stabshcal Results for Capacity Model Testing Using Different Weighting Factors for Me Major Skeet Right Tum Movement Constant Std Err of Y Est R Squared No.
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From page 69... ...
Testing Weighing Factors for the Major Street Through Movment at Multi-Lane Sites; 5-minute Mutual Data Table 34. Regression and Stabshcal Results for Capacity Model Testing Using Different Weighting Factors for Me Major Street Through Movement , ~.2' ,.p~................
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From page 70... ...
An increase In the toted canflichug flow can be achieved by introducing hither weighting factors for He conflicting streams. The first candidate stream was He major street reacts Field observation has shown that He major street left turn movement has a disproportionate effect on the minor street capacity compared with other movements.
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From page 71... ...
Regression and Statistical Results, Major Street Len Turn Weighting Factor Constant Std Err of Y Est R Squared No. of Observations Degrees of Freedom X Coefficient(s)
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From page 72... ...
Capacity Testing Results for Sites WE Nonnal Geometry and Traffic Flow Characteristics Table 39. Summary of Capacity Model Results Using Different Critical Gap and Follow-Up Time Values 16.89 lS7.16 O.SO 286 284 1.16 0.07 128 33.3% 1 .~.
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From page 73... ...
The recommended parameter values for the weighting factors for each traffic stream where applicable: 1 - through movement at single lane site; 1/n - Trough movement at multi-lane site when calculating vp fro minor left or minor nght, n is the number of through lanes; 0.5 - major street right turn movement (0 if channelized) ; 0.5 - opposing through and right turn movements, 2.0 - major street left turn movement.
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