Modeling Noise at Elevated Highways in Urban Areas: A Practical Application

Abstract

Traffic noise along highways is continuously increasing; with the projected growth in future traffic use, particularly near developing urban areas, it will not cease to increase. As a result, highway noise impacts are expected to be significant and mitigation strategies will undoubtedly be required. This paper presents a noise impact analysis along a coastal stretch of highway that forms the major entrance into the greater Beirut metropolitan area. Geometric layout includes a proposed 13 km elevated highway-viaduct with underlying service roads running parallel to an existing 4 × 4-lane highway currently accommodating an average daily traffic (ADT) volume of about 160,000 vehicles per day. The proposed viaduct is planned to be a BOT (build-operate-transfer) project and thus includes two toll plazas and three interchanges. Traffic flow characteristics including volumes, vehicular classification, and travel speeds were defined along the proposed coastal highway. Sensitive noise receptors were identified and noise measurements were taken during the noisiest periods. The FHWA traffic noise model was used to simulate base year and future noise exposure of adjacent land uses. The model was calibrated using the combination of field measurements and model predictions. Noise mitigation strategies were defined as well as the locations where they were deemed appropriate. The model was used to evaluate the efficacy of the proposed mitigation measures in satisfying absolute and relative noise-abatement criteria. Finally, the feasibility of implementation of relevant mitigation measures is discussed within the site-specific constraints.