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Trans. Planning Journal
| Title | Queuing Discharge Characteristics of Unopposed Left Turns |
|---|---|
| Author | Pin-Yi Tseng, Chiung-Wen Chang, Wen-Bin Chen |
| Summary | Protected left-turn phase, the so-called unopposed left turns, provide left-turn vehicles to discharge continuously under the situation with no conflicts of opposing through vehicles. The discharge behaviors of queuing vehicles are affected by geometric designs, traffic characteristic, and signal conditions. However, few domestic studies have focused on the queue discharge behaviors of unopposed left-turn vehicles. This study aims at this issue and collects field data amounted to 15 lanes and 18,771 samples. Data analyses showed that the traditional methodology used by saturation flow rate is inadequate estimating the capacity of these lanes or lane group. To improve the accuracy of the estimated capacity, this study used the direct estimating method suggested by 2001 Taiwan HCM. In addition, the average discharge headway after the fourth vehicle in queue is affected by left-turn speed and longitudinal distance of left-turn moving area. The passenger-car-equivalent of large vehicles and U-turn vehicles relative to left-turn passenger cars are 1.98 and 1.30, respectively. The formula for estimating the number of discharge vehicles in green and inter-green intervals is built. We also compared and discussed the queuing discharging behaviors of each lane in cases of 2 left-turn and 3 left-turn lanes. The results of this study could be referenced for estimating the capacity of unopposed left-turn lanes. |
| Vol. | 35 |
| No. | 2 |
| Page | 233 |
| Year | 2006 |
| Month | 6 |
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