EFFECT OF U-TURNS ON CAPACITY OF MEDIAN OPENINGS ON MULTILANE URBAN ROADS
Capacity of Median Openings
DOI:
https://doi.org/10.55766/sujst9238Keywords:
Median Openings, U-Turn, Empirical Model, Gap-Acceptance Model, VISSIMAbstract
Midblock median openings with U-turn provisions are commonly used in urban India to improve accessibility and reduce intersection conflicts. However, their capacity estimation under mixed traffic conditions remains complex. This study evaluates the applicability of the gap acceptance model and proposes an empirical approach to estimate U-turn capacity on multilane urban roads. Field data were collected from two locations in Hyderabad and Kurnool, and critical gap and follow-up time were estimated using Siegloch’s method. A linear empirical model was developed and validated using 61 observations collected from additional locations. A VISSIM simulation model was also calibrated for further analysis. The critical gap and follow-up time were found to be 4.33 and 2.50 seconds, lower than TRB 2010 values, indicating aggressive driver behavior. The empirical model performed well (R2 = 0.86; MAPE = 8.91%). At 2000 pcu/hr, gap acceptance and empirical models predicted capacities of 408 and 552 pcu/hr, respectively. Sensitivity analysis with β ranging from 0.71 to 0.73 showed significant changes in output, highlighting the need for local calibration. The findings offer practical insights for traffic engineers and planners to enhance the design and performance of U-turn facilities in heterogeneous traffic conditions.
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