Highway traffic noise and air pollution can have harmful effects on surrounding communities and neighborhoods. FHWA’s Traffic Noise Model (TNM) helps states determine when highway barriers can feasibly and reasonably be used to help mitigate the impacts of traffic noise.

Since the tool was originally launched in 1998, FHWA has released TNM six additional times to include critical updates and enhance analytical capabilities.

FHWA released TNM version 3.0 in February 2020, replacing TNM 2.5 that was released in 2004. This updated version includes significant changes to the user interface and provides improvements to the acoustics algorithms. These enhancements provide users with more flexibility and accuracy during the data entry process, as well as better visual representations when conducting noise analysis.

The U.S. Volpe Center has been involved with data collection and development of TNM since its inception, and the Center continues to improve TNM and related tools and provide technical support to the TNM user community.

TNM 3.0 helps highway agencies optimize noise barrier design, resulting in cost savings and noise reductions that will benefit the impacted communities. TNM 3.0 allows highway agencies to use base maps to more easily add objects to the study that are not already included, for example, in highway construction plans. This information provides a human-readable input format that others can write to in order to develop new methods for adding data to a TNM study. This capability provides long-term benefits to states by making workflows more efficient and keeping TNM current with the latest data formats.

U.S. DOT Volpe Center staff made significant improvements to TNM 3.0, including updates to the acoustical formulae, modernization of the acoustics code, and release of an enhanced graphical user interface. Accompanying the release of TNM 3.0, U.S. DOT Volpe Center experts also developed a number of documents and manuals including the model validation report, a technical manual, and a guide to help users get started with TNM 3.0. To assist FHWA in TNM 3.0 deployment, the U.S. DOT Volpe Center hosted two roll-out webinars, developed and published six instructional YouTube videos, and conducted user group virtual meetings.

The U.S. DOT Volpe Center continues to provide effective and comprehensive technical support to FHWA to address project-specific issues related to the implementation of TNM 3.0. Since its release in February 2020, the U.S. DOT Volpe Center has addressed 150 technical support issues, with roughly 10 percent involving detailed analysis utilizing the more maintainable programming code in TNM 3.0.

The U.S. DOT Volpe Center continues to assist FHWA in improving TNM. Based on feedback from the TNM user community, FHWA released TNM version 3.1 in January 2022. This new version features improvements to the analytical workflows, while the acoustic algorithms remain the same.

*This story originally appeared in the January 2021 publication: The U.S. DOT Volpe Center’s 2020 Annual Project Accomplishments, with updates to incorporate the recent release of TNM 3.1.