英文摘要 |
Protected left-turn phase, the so-called unopposed left turns, provideleft-turn vehicles to discharge continuously under the situation with no conflictsof opposing through vehicles. The discharge behaviors of queuing vehicles areaffected by geometric designs, traffic characteristic, and signal conditions.However, few domestic studies have focused on the queue discharge behaviors ofunopposed left-turn vehicles. This study aims at this issue and collects field dataamounted to 15 lanes and 18,771 samples. Data analyses showed that thetraditional methodology used by saturation flow rate is inadequate estimatingthe capacity of these lanes or lane group. To improve the accuracy of theestimated capacity, this study used the direct estimating method suggested by2001 Taiwan HCM. In addition, the average discharge headway after the fourthvehicle in queue is affected by left-turn speed and longitudinal distance ofleft-turn moving area. The passenger-car-equivalent of large vehicles andU-turn vehicles relative to left-turn passenger cars are 1.98 and 1.30,respectively. The formula for estimating the number of discharge vehicles ingreen and inter-green intervals is built. We also compared and discussed thequeuing discharging behaviors of each lane in cases of 2 left-turn and 3 left-turnlanes. The results of this study could be referenced for estimating the capacity ofunopposed left-turn lanes. |