The US Department of Transportation’s (USDOT) Bureau of Transportation Statistics (BTS) has released the initial National Transportation Noise Map, which reveals areas that are exposed to noise from aviation and Interstate highways.
The purpose of the new noise map is to facilitate the tracking of trends in transportation-related noise, by mode, and collectively for multiple transportation modes. The data allows users to view the national picture of potential exposure to aviation and highway noise, and also allows viewing at state or county levels. The geospatial data provides a basis for understanding ‘what-if’ scenarios and will help policy makers to prioritize noise-related transportation investments.
The Noise Map will be an addition to the BTS’s National Transportation Atlas Database (NTAD), a set of nationwide geographic databases of transportation facilities, networks, and associated infrastructure. The layers will now be updated on an annual basis, and future versions are envisioned to include additional transportation noise sources, such as rail and maritime.
The national, multimodal transportation noise mapping initiative used data sources from the Federal Aviation Administration (FAA) and Federal Highway Administration (FHWA) to create a comprehensive map of noise levels. The FAA’s Aviation Environmental Design Tool was used to model the average number of daily flight operations from airports across the country, excluding military operations. To determine daily road noise data, algorithms from the FHWA’s Traffic Noise Model were used in conjunction with data from the Highway Performance Monitoring System (HPMS) to obtain the average daily noise levels for automobiles, medium trucks, and heavy trucks.
The acoustics modeling used in the Noise Map represents a worst-case scenario, and shielding effects are not included. The acoustics modeling used in developing these noise layers uses conservative, simplified methods, and only considers transportation noise, with no other ambient noise sources. The noise data in the layers should be used for tracking trends, not for assessing impacts, and only represents the first year of data that can be used to analyze future trends. While only National Highway System Interstates are included in the estimate of percentage of population affected by road noise, additional road types are included in the dataset.
Using the Noise Map data, BTS highlighted the percentage of total USA resident population that had the potential to be exposed to ‘A-weighted’ 24-hour equivalent sound levels (LAEQ) from aviation and Interstate road noise in the year 2014. A-weighting is a correction applied to sound levels to better reflect the way the human ear hears sound, and are described by the unit dBA.
The data shows that more than 97% of the USA’s population has the potential to be exposed to noise from aviation and Interstate highways at levels below 50 decibels or roughly comparable to the noise level of a humming refrigerator. A much smaller segment of the population has the potential to be exposed to higher levels of transportation. Less than one-tenth of a percent of the population could potentially experience noise levels of 80 decibels or more, equivalent to the noise level of a garbage disposal.