AASHTO Noise Working Group Sound Bites

Sound Bites 2/11/2021


  • Alabama DOT Noise Policy is in process of being updated in 2021 (5-year update).


  • Caltrans has four projects which examined the placement and distribution of vehicle sub-source energy which is used for noise impact analysis. This has large highway design implications for alternative noise mitigation strategies. Numerous studies using advance acoustic measurement techniques show current assumptions in the FHWA Traffic Noise Model analysis software incorrectly assign too much vehicle energy to 5 and 12 ft positions above the pavement.
  • Caltrans did a technology demonstration project for mapping pavement acoustics, lane by lane, on a six-lane-24-mile-long corridor in the Silicon Valley. The study combined OBSI pavement acoustic measurements with GPS and this data was then mapped to a GIS web-based server for other stakeholders to access. A color code scale visually indicates where the pavement is quiet and loud and its relative position to nearby roadside residential receptors. The pavement variation can be greater than 10 dB (will sound twice as loud) and the correlation to roadside noise levels is almost 1:1.  A quieter pavement rehabilitation strategy could lower the tire/pavement noise by 8-10 dBA, and the roadside noise level will also be reduced by about 8-10 dBA. This is very useful information and an important tool for addressing noise complaints and planning pavement rehab projects. A 19-page 2021 TRB paper is available for more project details
  • A second Caltrans’ project explored using the User Defined Vehicle function within TNM to reposition Heavy Truck 12 ft energy to the shorter Medium Truck 5 ft position. This shorter 5 ft energy distribution would more closely match energy distributions determined by the NCHRP 842 Beamforming research. This software ‘tweak’ would allow noise modelers to continue to use TNM and improve its’ accuracy. Ultimately, this modeling approach could better quantify insertion loss for shorter, less-expensive barriers and would provide another much-needed lower-cost noise mitigation option. The full TRB 2021 paper describing the project is available for download at the TRB 2021 winter conference. Contact Eric Moskus and Peter Hardie of ICF International.
  • A third Caltrans’ research effort used the more advanced SoundPlan Noise analysis software which has FHWA’s TNM code embedded in inside it. SoundPlan allows more flexibility to explore repositioning vehicle energy to different heights above the pavement other than the locked 0,5,12 ft positions inside TNM.  This simulation exercise compared TNM 2.5 calculations with NCHRP 842 energy distributions (between 0 to 3.3 ft above the pavement), and the impact these very different energy distributions had on the performance of short barriers. A 2021 TRB paper was written and is available as an InterNoise 2021 paper from Dana Lodico.
  • A fourth Caltrans research project examined the acoustic insertion loss of a short earthen berm. Like the Ohio DOT berm studies, a very large reduction in noise levels was measured. Noel Alcala, of Ohio DOT, was one paper reviewer who was very excited that the study closely confirmed his Ohio DOT berm studies. The paper’s author, Paul Donavan, has won ADC40/AEP80 paper-of-the-year award five times in the past.  This paper hinted that the TNM assumptions on vehicle sub-source positioning may not be accurate.


  • CDOT’s guidance was approved by FHWA and was published in October 2020


  • Idaho DOT is hoping to get their noise policy approved in February 2021.


  • Ohio DOT will be awarding noise wall construction projects in Akron, Columbus, Canton, and Toledo in 2021.  Two projects in Akron consist of 442,000 SF and 5.4 miles of noise wall.
  • Ohio DOT is starting a small scale research project regarding the Shielding Effects Of Low-Height Walls/Safety Barriers On Heavy Truck Noise.  The objective is to analyze the potential shielding effect of low barriers, such as concrete safety barriers, adjacent to Ohio highways and determine if the resulting noise still includes noise attributed to upper heavy truck noise sources (e.g., exhaust stack).
  • Ohio DOT completed research regarding Air Quality Effects From Noise Walls And Vegetated Noise Walls.  Air monitoring for particulate matter with median diameter of 2.5 microns (PM2.5) was performed in order to assess the effect of roadside noise barriers along highways on traffic-related particulate matter pollution in adjacent neighborhoods. The project was intended to determine if noise barriers could be used as protection from near-road air pollution.  The hypothesis was that roadside noise barriers would mitigate traffic-related particulate matter pollution in adjacent neighborhoods.  The report concluded that noise barriers did not diminish PM2.5 exposure in residential areas adjacent to roads when compared to control sites where noise barriers were not present.  The results of the sampling indicated that there was not a significant decrease in PM2.5 due to the noise barriers.  These results are not according to expectation, but the conclusion is the only one that can be drawn from the data. The main limitation for this study was the amount of data collected. For more info, contact Noel Alcala at noel.alcala@dot.ohio.gov.
  • Ohio DOT is beginning a Vinyl fence noise wall research project in March 2021. The project involves constructing two 8’ tall vinyl fences at two different locations and testing them for noise reductions and comparing the reductions to nearby concrete noise walls.  Also included is testing of existing 7’ and 8’ tall vinyl fence noise walls in Ohio.


  • VA DOT is widening I-66 both inside and outside the beltway. The projects are approximately 23 miles in length and extend through multiple cities and counties including – Arlington County, Fairfax County, City of Fairfax, Town of Vienna and Prince William County. The I-66 projects are currently under construction and are expected to result in the construction of over 1.9 million Square Feet (SF) of noise barriers (new barriers and in-kind barrier replacement).
  •  VA DOT has a project is in Fredericksburg Virginia, I-95 Express Lanes Extension (FRED EX).   The project area extends approximately ten miles and primarily consists of extending two reversible Express Lanes in the median of I-95. The project will add approximately 240,000 SF of noise barriers.
  • VA DOT has an I-64 Hampton Roads Bridge Tunnel (HRBT) project. The purpose of the project is to expand the Hampton Roads Bridge Tunnel . The project is in Hampton and Norfolk and is approximately 10 miles long. The project will add approximately 377,000 SF of noise barriers

West Virginia

  • WVDOH is waiting on the new FHWA noise regulation before updating their policy.


  • A new series of noise related on-demand web-based training is under development at the National Highway Institute [ www.nhi.fhwa.dot.gov ].  The third and final batch of the NHI’s pilot on-demand noise-training courses was closed to reviewer comments on Jan 26, 2021. This completes the development phase where a select number of volunteer reviewers could take the new noise training courses and submit feedback to the course developers.  The new noise courses involved in the volunteer review phase include the following:  Acoustics of Highway Traffic and Construction Noise, Highway Traffic and Construction Noise Regulations, How to Measure Highway Traffic Noise, Abatement and Design Considerations for Highway Traffic Noise, An Introduction to the Traffic Noise Model (TNM) 3.0, Public Involvement for Highway Traffic and Construction Noise Projects.

Sound Bites 11/17/2020


  • Caltrans spent the first half of 2020 examining ways to implement NCHRP OBSI and beamforming research results for more accurate noise modeling. The slow pace of TNM development and its’ inaccuracy for detailed modelling is driving this effort.  Two different approaches were explored, using either TNM 2.5 or the much more advanced SoundPLAN software. This effort included creating a custom software patch, by inhouse SoundPLAN programmers, for the SoundPLAN portion of the analysis.  Some of this exploratory work will be submitted for potential presentation for TRB 2021.


  • Colorado’s draft noise guidance is currently under review by FHWA HQ.


  • Idaho Transportation Department (ITD) is in the process of revising its 2011 noise policy.  Among other changes, this new policy incorporates the use of FHWA Low Volume Road Tool.


  • Illinois DOT is currently in the process of streamlining and expediting their approval process of alternative noise barriers.


  • Iowa is working on a tool to predict noise barrier costs into the future utilizing buffering within a geographic information system, based on residential lot density, residential distance from the highway, and traffic volumes.


  • Kentucky KYTC and FHWA have updated the KYTC Noise Policy.  The new policy went into effect July 1, 2020.


  • Elton Holloway, Mississippi DOT’s resident expert on all things noise and air quality related, has retired after an incredible 45 years of service.


  • Missouri, despite funding slowdowns, continues to have many Type I projects currently going through studies.  Additionally, Missouri is producing an informational video for public consumption.  The video is basically about our noise process with some education on the fundamentals of highway traffic noise.  We intend to use it at public meetings and on MoDOT websites for educational purposes.


  • The Reno Spaghetti Bowl project is underway.  The first phase will include reconstruction of existing sound walls and the placement of visual screening walls from the Truckee River south to Mill Street as part of the noise mitigation and environmental justice commitments.


  • Ohio is kicking off a Vinyl fence noise wall research project in January 2021. The project involves constructing two 8’ tall vinyl fences at two different locations and testing them for noise reductions and comparing the reductions to nearby concrete noise walls.
  • Ohio’s Noise Model To Monitor Case Study research is on-going.  Preconstruction readings were completed.  Modeling is on-going.  Post construction readings are the next steps.  The research will compare modeled results to measured results.
  • Ohio awarded a noise wall maintenance project in Canton Ohio involving resealing concrete and aluminum panels and patching sound absorptive material.
  • Ohio will be awarding a Type II noise wall project in Toledo in September.  The project involves constructing 2.3 miles of noise wall consisting of 180,000 SF for communities that predate the freeway.
  • Ohio is conducting research regarding Air Quality Effects From Noise Walls And Vegetated Noise Walls.  A report will be completed by end of 2020.
  • Ohio is initiating a small scale research project regarding the Shielding Effects Of Low-Height Walls/Safety Barriers On Heavy Truck Noise.

South Dakota

  • Long-time noise expert, Alice Whitebird, retired in June.  SDDOT finished updating a draft of state noise guidance.  It is being reviewed by our administration then onto FHWA.  This will be SDDOT’s first update since 2011.  SDDOT has one current noise study ongoing with feasible/reasonable criteria met at one location.  SDDOT is going through the public involvement process and will begin balloting soon.


  • Texas has many noise barriers coming down the pipeline in El Paso, Dallas, Fort Worth, Austin, San Antonio, and Houston.   Texas also has some longitudinal tining projects and some with porosity free concrete (PFC).