The estimation of critical gap is an important traffic parameter and this is useful to estimate the capacity of U-turning vehicles at uncontrolled median openings. In this study critical gap is estimated by four different methods by collecting data at seven median openings in Turkey. An unconventional method of critical gap estimation using the merging time of the U-turning vehicle is proposed. The merging time to clear the conflict area at uncontrolled median opening was calculated from field data and this time is utilized to estimate the critical gap for different categories of vehicle.
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