The American Soundscape. Introducing the National Transportation Noise Map

I can’t believe I’ve only just discovered the National Transportation Noise Map. I found it online by chance while doing research for another article a few days ago and have been playing with it, almost addictively, ever since!

The National Transportation Noise Map gives a comprehensive view of transportation noise across the United States. It draws what is known as the “soundscape” of transportation-related noise in America. The map allows for the exploration and comparison of various transportation noise sources, including aviation, rail and roads. It also includes information about the magnitude and distribution of the noise levels generated from these sources.

The map provides users with easy-to-understand visuals of the noise sources, such as sound contour maps of airports, railroads, and highways. It also allows for comparison between multiple locations to better understand how changes in land use or transportation infrastructure may impact the surrounding environment.

Who created the National Transportation Noise Map?

The National Transportation Noise Map was created by the U.S. Department of Transportation’s Bureau of Transportation Statistics (BTS).

The map is designed to help government officials and planners make informed decisions when evaluating alternative transportation projects or policies. It can be used to determine the potential effects of a project on local soundscapes, as well as identify which areas are most impacted by existing transportation noise sources. For example, this map could help decision-making organisms prioritize one area over another for noise-reducing asphalt repaving.

How accurate is it?

Well, is definitely not 100% precise, but it doesn’t need to be. As long as we understand what it is that we are looking at, this map can still be a very useful tool.

The first thing we need to understand is what does the information on this map represent. It represents the average noise at any given coordinates, over a period of 24 hours, averaged over a 1-year span. In other words an average full day. This means the map does not show pick-hours traffic or temporary noise sources such as sporadic construction sites.

The second thing we need to understand is how all this data was collected, or in most cases, calculated. The data you see on the map comes from a variety of sources. Some are actual readings from noise receptors located throughout the country. Others are actually statistically calculated based on traffic volume reports. For example for rail road generated noise BTS says that:

General Transit Feed Specification (GTFS) data are used in conjunction with the North American Rail Network (NARN), and FRA’s Highway-Rail Crossing Inventory to obtain operational data, route information and locations of grade crossings, tunnels, and quiet zones.  

National Transportation Noise Map documentation

This means that BTS didn’t take any sound readings along most of the American railroad system. Instead, they took the available information on the railroad routes and frequency and combined that with the dB reading we know certain trains produce to determine how much noise each coordinate was exposed to over an average 24-hour period.

Or in the case of how road noise was calculated, BTS states the following:

Road noise is computed within the NTNMT using acoustical algorithms from the Federal Highway Administration’s (FHWA) Traffic Noise Model (TNM) version 2.5.

National Transportation Noise Map documentation

So again, there isn’t a microphone every mile along every single road in the US, that would be crazy. Instead, average traffic information was used in combination with mathematical models to calculate the average sound exposure at any given point.

One last thing to consider is that even though transportation accounts for a big part of the noise pollution in our country, it is not the only one. This map does not contemplate any noise source that isn’t transportation-related, and therefore doesn’t offer the full picture, or I should say soundscape, of a given location. Still, in most cases, it does show a pretty good approximation.

How often is it updated?

The National Transportation Noise Map was first released in 2014 as a prototype. The most recent version was released in 2020 and shows information from 2016 and 2018.

The goal of this project is to identify trends in transportation noise pollution and to provide a consistent way of measuring noise levels around the country, so constantly updated information isn’t actually needed.

We do not know when a new update will come out, but the future of this map sure is an exciting one. With continued technological advancements, it will become increasingly accurate and useful for those looking to evaluate transportation projects or policies in their area, and for noise freaks like me!