The National Academies

NCHRP 25-66 [Active]

Reviewing the REMEL Noise Database to Accommodate the Current Vehicle Fleet

  Project Data
Funds: $1,000,000
Staff Responsibility: Dr. Zuxuan Deng
Research Agency: Cross Spectrum Acounstics
Principal Investigator: Dr. Judith Rochat
Effective Date: 12/5/2023



Highway noise is always a top environmental concern with the public on any highway project. The Reference Energy Mean Emission Level (REMEL) database is an inventory of different vehicle pass-by noise levels that is the basis for the Federal Highway Administration (FHWA) Traffic Noise Model (TNM) analysis software. It is 25 years old and in need of updating due to changing vehicle fleet characteristics. Newer noise measurement technology has also evolved, and it can be applied to locate and quantify noise generators on a moving vehicle. The REMEL database directly affects noise impact and mitigation analyses on federal-aid projects. 

Research is needed to update the highway noise dataset using existing and new highway acoustic measurement technologies to account for the change in the vehicle fleet. 


The objective of this research is to update the REMEL noise database to account for new vehicle fleet with focus on 

  1. Newer passenger car (PC) types, 
  2. Medium truck (MT), 
  3. Heavy truck (HT), and
  4. Electronic vehicle (EV).

At a minimum, the research team should use three acoustic measurement technologies (beamforming, wayside sound level, and on-board sound intensity [OBSI]) that will better quantify the position and distribution of vehicle noise sub-sources: mechanical, exhaust, tire/pavement, and aerodynamic sources.

Accomplishment of the project objective will require completion of the following tasks, at a minimum.







Task 1. Review the pertinent literature on computational and acoustical source visualization methodologies; highway noise measurement, practices, and techniques; and the latest industry standards of acoustical source characterization and vertical distribution of sound energy at source. Identify ongoing, relevant research projects and obtain any interim materials, if available. Identify any needed coordination with other ongoing research projects.


Task 2. Develop or identify standardized methodologies for beamforming, wayside sound level (isolated passby), and OBSI, and for acoustical source characterization and vertical distribution (from 0 to 14 ft) of sound energy at source that determine the optimal microphone array resolution and frequency range of the system. Describe validation and calibration methodologies for all three noise measurement technologies. Beamforming measurements should be accompanied and be conducted simultaneously with wayside measurements.


Task 3. Submit a technical memorandum summarizing findings from Tasks 1 and 2.


Task 4. Conduct a virtual meeting with the NCHRP panel to discuss findings from Tasks 1 and 2. Receive feedback and guidance to proceed with Task 5.


Task 5. Develop a detailed data collection plan. At a minimum, the plan should cover:


Measurement Sites

  • Number of sites (minimum 4 pavement types x 5 regions) for each pavement type (at minimum: dense-grade asphaltic concrete [DGAC], open grade asphaltic concrete [OGAC], and Portland cement concrete [PCC] (longitudinally tined concrete and transverse tined concrete) in good condition)
  • Site characteristics, similar to descriptions given in FHWA-PD-96-008: Development of National REMEL for the FHWA TNM Section
  • Recommend geographically diverse locations to represent national fleet and landscape varieties ·        


Vehicle Characteristic

  • Vehicle type: PC, MT, HT (high and low exhaust), and any bus or motorcycles that come through
  • Number of axles
  • Propulsion type: internal combustion engine (ICE)/electronic/hybrid
  • Operating Condition
  • Idle
  • Constant flow speed range, e.g., 25 to 85 mph
  • Acceleration for all vehicle types
  • Truck crawling for high roadway grade·        


Data Collection

  • Device placement of wayside SLM and beamforming array, e.g., for wayside SLM: 25 ft and 50 ft from the center line of the nearest travel lane at height of 5 ft and 12 ft,
  • On-site verification and reporting of proposed sites
  • Applicable frequency ranges, e.g., 50 to 10,000 Hz for wayside SLM, 400 to 5000 Hz for OBSI and 500 to 10,000 Hz for beamforming or better if available
  • Non-acoustic data: vehicle speed, meteorological, video, synchronized time log, data logs, site location (latitude, longitude, elevation), etc.
  • Quality assurance and quality control plan
  • Minimum data for each vehicle/operating condition/pavement type, e.g., 30 events for uncommon conditions such as MT/constant flow between 25 and 30 mph/OGAC and 100 events for common conditions such as auto/constant flow between 55 and 60 mph/DGAC          


Dataset Structure and Format 

  • Open-source digital format for immediate use by state DOTs and public
    • E.g., wayside sound level meter (SLM): max one-third octave A-weighted equivalent sound level (LAeq)-1/2 sec, maximum A-weighted fast time averaged sound level (LAfmax) time history for full pass by (-10, max, -10 dB) at ½ sec intervals
    • E.g., OBSI, final one-third octave sound intensity level (SIL) results for each test section
    • E.g., beamforming, overall and one-third octave band level distributions as a function of height
  • All relevant non-acoustic data


Task 6. Prepare Interim Report No. 1 documenting the results of Tasks 1 through 5 and provide an updated plan for the remainder of the research no later than 6 months after contract award. The updated plan must describe the approved methodology and rationale for the work proposed for Phases II and III. 






Task 7. Execute the data collection plan based on approved Interim Report No. 1. Conduct bi-monthly status call with the NCHRP panel during the entire data collection period.

Task 8. Submit the three collected data sets (beamforming, wayside sound level, and OBSI) in a digital format as approved in Interim Report No. 1 and a summary of findings to the NCHRP.


Task 9. Document the differences in approach from the FHWA-PD-96-008: Development of National REMEL for the FHWA TNM report.


Task 10. Prepare an annotated outline for the NCHRP report. The measurement process, data collection and findings should be thoroughly documented, to be subsequently implemented by FHWA into the FHWA TNM software to improve its accuracy, be continually maintained, and be updated in the future.


Task 11. Prepare Interim Report No. 2 that documents Tasks 7 through 10 and provide an updated work plan for the remainder of the research no later than 18 months after approval of Phase I. The updated plan must describe the process and rationale for the work proposed for Phase III. 





Task 12. Prepare and submit the draft NCHRP report based on approved Interim Report No. 2 for the NCHRP panel’s review.


Task 13. Prepare the final deliverables including the following:

  1. Final NCHRP report;
  2. Final data sets, including raw data;
  3. Media and communication material (e.g., PowerPoint presentations, 2-page executive level flyer, graphics, graphic interchange format (GIF)s, press releases); and
  4. A stand-alone technical memorandum titled “Implementation of Research Findings and Products.” Additional funding may be available for a follow-up contract on the implementation of the results.



STATUS: Research in progress.

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