Estimation of optimum speed limit on urban expressway: case study of Delhi-Meerut and Greater Noida Expressways

OBJECTIVE: This study introduces a data-based approach for determining the speed limits on urban expressways, using the Delhi-Meerut and Greater Noida Expressways as case study. It also aims to evaluate the relationship between speed behavior characteristics and crash frequency, and to identify optimal speed limits that can enhance road safety while maintaining traffic efficiency. METHODS: test. RESULTS: The XGBoost model demonstrates better predictive accuracy; nevertheless, the NLR model is favored for its clarity and simplicity in reverse calculations to determine the ideal speed limits. Utilizing the NLR-based model, crash forecasting is employed to establish acceptable thresholds for crash rates, and suitable optimal speed limits are suggested for expressway sections. Optimization findings indicate that the existing speed limits for two Expressways, 70 km/h for cars and 50 km/h for heavy vehicles and 75 km/h for car and 50 km/h for Heavy vehicle surpass the safe levels, optimal limits are projected to be 60 km/h for cars and 40 km/h for heavy vehicles on Delhi-Meerut Expressway and 70 km/h for cars and 45 km/h for Heavy Vehicle on Greater Noida Expressway. Moreover, variable speed limits influenced by time-of-day patterns were suggested, advising 65 km/h during off-peak times and 55 km/h during the peak traffic hours. CONCLUSIONS: This study provides an empirical basis to bolster speed management strategies focused on improving road safety in high-speed urban routes in India. The findings highlight the importance of adopting data-driven and dynamic speed limit policies that consider real-time traffic conditions and speed behavior characteristics. The approach can be extended to other urban expressways with similar traffic conditions, contributing to the development of safer and more efficient transportation systems.