Developing a Causal Model to Quantify the Impact of Vehicular Speed on Environmental Noise Descriptors in Urban Flyover Corridors

This empirical study investigates the contributory factors of traffic-generated environmental noise in urban corridors, specifically comparing at-grade and above-grade (flyover) road links. By analyzing noise descriptors and indicators across 24 locations in Nagpur, India, the research establishes a significant non-linear relationship between vehicular speed and noise generation. The findings reveal that ambient noise levels at all studied locations exceeded permissible limits for their respective land uses. Notably, noise intensities were significantly higher on access-controlled above-grade links compared to at-grade locations, despite the latter carrying higher traffic volumes and densities. Data indicates a standard deviation of 3–4 dB(A) between these levels, with above-grade environments showing 50% less variability, suggesting a more constant and intense noise state. The study concludes that vehicular speed—averaging 42 km/h on flyovers versus 23 km/h at-grade—is the primary driver of elevated noise levels rather than traffic volume. These results underscore the potential health hazards of high-speed urban interventions and provide a critical aid for stakeholders in planning, policy drafting, and the implementation of noise mitigation strategies.