<![CDATA[This study aims to evaluate the performance of existing and alternative U-turn geometric configurations in terms of vehicle speed and queue ratio under varying U-turn demand and traffic directions. Field survey data were analyzed using the Indonesian Highway Capacity Guidelines (PKJI 2023) to determine traffic volume, roadway capacity, degree of saturation, and vehicle speed. A microscopic traffic simulation was subsequently conducted using PTV Vissim to compare the existing U-turn configuration with two alternative geometric designs. The simulation considered U-turn proportions of 5%, 10%, 15%, 20%, and 25% in two traffic directions. Vehicle speed and queue ratio were used as the primary performance indicators. Under the existing configuration, peak-hour vehicle speed decreased to 21.5 km/h in the Margonda Raya direction, while the queue ratio reached approximately 2.8 when 25% of vehicles performed U-turns. Alternative geometric configurations improved traffic performance by increasing vehicle speed and reducing queue formation. Under the same peak-hour condition and 25% U-turn proportion, Alternative 2, a roundabout-type U-turn configuration, increased vehicle speed from 21.5 km/h to 33.19 km/h and reduced the queue ratio from 2.8 to 0.66 in the Margonda Raya direction. However, the effectiveness of the alternatives varied by traffic direction, with Alternative 1 delivering better queue performance in the Bogor Raya direction. The findings indicate that U-turn geometric performance is dependent on both U-turn demand and directional traffic characteristics. Therefore, U-turn design selection should not rely on a single geometric configuration but should consider traffic demand, directional flow characteristics, available road space, and operational performance.]]>
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