Exploring the relationship between traffic, speed, and personal in-vehicle noise exposure during commutes.

While roadway noise is well-documented, research seldom quantifies the more critical in-vehicle exposure or evaluates the factors that modify it under real-world conditions. This study addresses this gap by investigating how traffic volume and driving speed, two key determinants in transportation planning, influence interior noise levels. Furthermore, we evaluate shifting commute times from rush hour to off-peak periods as a potential noise mitigation strategy. We collected 1-minute noise and GPS data from 148 vehicle trips taken by 14 participants in Hartford County, US. To evaluate how the departure time of morning commutes to work impacts noise exposure, we compared noise levels during a rush-hour commute (6:30-8:30 am) to a non-rush-hour commute for each participant. The median 1-minute noise level was 69.4 dBA (IQR = 65.7-74.1). Nine percent of measurements exceeded 80.0 dBA, the threshold of potential long-term hearing damage. Mixed-effects modeling showed both traffic volume and driving speed were positively associated with interior noise, with IQR increases linked to noise increases of 1.18 dBA and 0.71 dBA, respectively. However, substantial unexplained variability in the model suggests that other factors significantly influence noise levels more. The trip-averaged noise levels did not vary significantly between rush-hour (median = 70.7 dBA) and non-rush hour (median = 72.4 dBA) commutes (p = 0.84). This indicates that shifting commute times may not effectively mitigate overall noise exposure. Instead, strategies targeting overall traffic reduction may be more impactful. By linking vehicle interior noise to traffic characteristics and travel behavior, this study provides an interdisciplinary basis for transportation policies and traffic management reducing the environmental health burdens of commuting.