Design Guidance for Channelized Right-Turn Lanes (2014) / Chapter Skim
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Chapter 4. Traffic Operational Analysis of Channelized Right-Turn Lanes This chapter presents the results of a traffic operational analysis of channelized right-turn lanes conducted with the VISSIM simulation model.
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Traffic Operational Modeling 4.1 The majority of the traffic operational studies were performed using simulation modeling, which can test many design, traffic volume, and pedestrian volume combinations. Simulation modeling allows for the evaluation of vehicle-to-vehicle and vehicle-to-pedestrian interactions in a controlled environment.
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Each configuration is described below. Configuration 1 is a typical signalized intersection with a conventional (i.e., nonchannelized)
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Configuration 3 assumes a signal-controlled channelized right-turn lane. The evaluation for this configuration focused on the differences in right-turn delay due to signalization of the right turn assuming similar signal timing to that assumed in Configuration 1.
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VISSIM simulation can result in various saturation flow rates depending on a number of factors. A series of tests were conducted to determine the correct set of safety distance parameters to produce results similar to those produced by HCS and Synchro.
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As shown above, the VISSIM results for right-turn delay matched the field measurements at the intersection in Portland, and were only 0.9 sec (13.3 percent) lower than the field measurements for the site in Boise.
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Figure 17. Delay Comparison of Configuration 1 - Conventional Right-Turn Lane (With and Without RTOR)
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Figure 18. Delay for Configuration 2 (Yield-Controlled Channelized Right-Turn Lane)
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As shown in Figure 19, the right-turn delays ranged from approximately 14 sec for a rightturn volume of 100 veh/h to approximately 20 sec for a right-turn volume of 500 veh/h. This is compared to approximately 15 and 29 sec, respectively, for Configuration 1.
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The yield-controlled channelized right-turn lane has the lowest delay of the three configurations. At very low right-turn volumes, the impact of a yield-controlled channelized right-turn lane compared with a conventional traffic signal with RTOR is relatively small.
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The greater reduction in delay that results from the increase in conflicting through traffic volumes is likely because the RTOR vehicles for Configuration 1 require a larger gap in traffic than the merging vehicles for Configuration 2 during the red signal phase. Figure 22 shows a similar comparison with the Configuration 1 without RTOR option.
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• For Configuration 3 (signalized channelized right-turn lane) , delay is generally not impacted by the volume of conflicting traffic on the cross street, unless the signal timing is changed to accommodate conflicting traffic volumes.
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would be experienced in a location in which a portion of the vehicles do not yield to pedestrians approaching the crosswalk. Figure 23.
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Figure 24. Delay Due to Pedestrian Crossings -- Configuration 2 Channelized Right-Turn Lane (800 veh/h Conflicting Through Volume)
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Figure 25. Pedestrian Delay Waiting for a Gap in Right-Turning Traffic 4.3.4 Summary of Results for Pedestrian Impacts on Traffic Operations The results of the pedestrian analysis are summarized below: • Pedestrian volume increases right-turn vehicle delay by 50 to 70 percent for Configurations 1 and 2.
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Impacts of Geometric Characteristics and Signal Phasing on 4.4 Channelized Right-Turn Lane Delay The geometry of the channelized right-turn lane for Configuration 2 as well as the type of signal phasing for Configuration 3 are thought to affect the delay experienced by right-turning vehicles. The VISSIM simulation models created for the delay studies were used to quantify the relative impact of these factors: • Addition of an acceleration lane (Configuration 2)
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4.4.2 Channelized Right-Turn Lane Radius and Speed Impacts The effect of channelized right-turn lane radius on right-turn delay was evaluated by changing the speed of the channelized right-turn lane for various conflicting through volumes and for two roadway speeds. Vehicle speed along the channelized right-turn lane was used as a surrogate for channelized right-turn lane radius, since vehicle speed is limited on narrower curves (smaller radius channelized right-turn lanes)
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Figure 27. Right-Turn Overlap Table 12 compares the delay for the base condition to providing additional green time through use of an overlap signal phase.
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4.4.4 Summary of Results for Geometric and Signal Element on Channelized Right-Turn Lane Traffic Operations The results of the geometric and signal operations analysis of right-turn delay suggest the following: • Acceleration lanes substantially reduce right-turn delay at all volume levels. • Increasing the radius of the channelized right-turn roadway reduced the delay by approximately 10 to 20 percent for each 8 km/h (5-mi/h)
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• Increasing the radius of the yield-controlled channelized right-turn lane from approximately 5 to 6 m (15 to 20 ft)
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