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Update the National REMEL Database Used in FHWA Traffic Noise Model


The Reference Energy Mean Emission Level (REMEL) database is an inventory of different vehicle noise levels which is used in the FHWA Traffic Noise Model analysis software. It is 25 years old and in need of updating. Internal combustion engines have become more efficient, overall vehicle technology has evolved, truck stack noise has decreased, and electric and hybrid vehicles are entering the vehicle population. Newer noise measurement technology has also evolved, and it can be applied to more accurately locate and quantify where on the vehicle, the noise is being generated. The old REMEL database positions and distributes a significant amount of vehicle noise energy at 5 and 12 feet above the pavement. Recent NCHRP research shows that most vehicle noise energy is at the tire/pavement interface or only 3.3 feet above the pavement. The tall, 5- and 12-foot distributions in the old REMEL database, means the current noise analysis software is strongly biased toward determining that only tall and expensive sound walls will work and it also underestimates reductions which shorter berms and concrete safety barriers can provide. The old REMEL database also underestimates the acoustic variation of different pavements and how the different pavements influence roadside noise levels. This outdated REMEL database adversely impacts sound wall analysis and limits design options available to state DOTs. Tall sound walls are about $2M/mile and shorter less-expensive noise barriers would provide state DOTs much more flexibility in mitigating highway noise impacts and would save a significant amount of taxpayer dollars.

This research will use the two new highway acoustic measurement technologies of OBSI and beamforming, in combination with the old measurement process - SPL, to develop a new REMEL database for the current vehicle fleet. All the five basic acoustic vehicle classifications: heavy truck, medium trucks, passenger cars, buses, and motorcycles will be remeasured and updated. The beamforming will show where the vehicle noise is truly positioned in the vehicle profile and the OBSI will more accurately measure the pavement acoustics and how it correlates to roadside noise. These two new measurement processes will be combined with the old-school, roadside SPL measurements. Based on previous NCHRP research, this will lower the old-and-outdated 5 ft and 12 ft vehicle positions and more accurately distribute the noise energy in the vehicle profile. This new REMEL database could then be used to update and improve the accuracy of the FHWA TNM software.

Updating and improving the vehicle noise REMEL database will improve the accuracy of traffic noise analysis and provide state DOTs more options and flexibility to mitigate the environmental impacts of highway noise.


The final product will be an updated vehicle noise REMEL database based on the current vehicle fleet and measured with both old and new acoustic measurement technologies which will better quantify and position the vehicle noise sources. The new REMEL database could ultimately be implemented into the FHWA TNM software to improve its accuracy. A preliminary analysis will also be included with the database to discuss the differences between the new REMEL database and the older REMEL data.

Noise levels will be measured for different acoustically-isolated individual vehicles operating under different conditions in different roadway environments using SPL, OBSI, and beamforming acoustic measurement technology. The measurement matrix would include: different vehicle types, different speeds (10 to 80 mph), cruising and acceleration and deceleration conditions, flexible and rigid pavements, and different road grades.

The REMEL database should be thoroughly documented and the data made available in an open-source or spreadsheet-based format for immediate use by state DOT engineers and noise analysts and other noise simulation software vendors such as SoundPlan and CADNA. To accommodate future updates and improve accuracy and limit computational adjustment factors, the REMELs will be measured near the source and referenced relative to the vehicle position in the traffic lane and will not be based on measurements taken at a distant receptor position. Most noise barrier design is performed on federally funded public works transportation projects and the REMEL database directly impacts structural noise barrier design. All stages and phases of the development of the REMEL database will be managed and reviewed by an experienced and responsible registered engineer. Implementation into the FHWA TNM software is not included in this research and would be another separate process.


The older REMEL database is based upon a 25-year-old vehicle fleet, incorrectly distributes noise energy too tall above the pavement, and doesn’t accurately account for pavement variation and its impact on roadside noise levels. An updated REMEL database would improve the accuracy of noise impact analysis and provide more noise barrier options.

The old REMEL database biases noise analysis to favor tall expensive sound walls which may not be reasonable or feasible and may not make it into the final highway project. Noise reduction provided by shorter less-expensive noise barriers is inadequately quantified. When sound walls are dropped from a project because they were not acoustically feasible or economically reasonable, noise-impacted roadside communities are very upset when no noise barrier is installed. Less-expensive shorter noise barrier options are urgently needed by state DOTs.

This research would provide State DOTs with less-expensive noise barrier options and more flexibility in mitigating noise impacts of projects. Between 2014 and 2016, $224 million was spent on noise walls annually in the United States. If this cost were to be reduced by even a small percentage, the result would be tens of millions of taxpayer dollars saved annually. Regardless of how much money is ultimately saved, more realistic modeling of noise abatement will ensure that the money invested in noise barriers is used wisely.

Related Research:

The 1996 REMEL database was developed under a transportation pooled fund research project and included 25 state DOTs and measured about 6000+ individual vehicles in about six different states. This proposed research will use some of the methodology of the old 1996 REMEL study and include the work done under recent NCHRP 630, 635, and 842 projects which validated the new OBSI and beamforming measurement technologies. NCHRP 630 measured the pavement acoustic variation for both light vehicles (passenger cars) and heavy trucks. NCHRP 635 and 842 measured about 1600 individual heavy trucks and a few medium trucks and passenger cars. This proposed research would combine measurement procedures of the old 1996 REMEL study with the new NCHRP measurement technologies to create an updated REMEL database which would be about 6000+ vehicles and include heavy trucks, medium trucks, passenger cars, buses, motorcycles, and newer all-electric or hybrid vehicles.


Cooperation with FHWA will be vital to ensure this updated REMEL database will be adopted and implemented into FHWA’s Traffic Noise Model software as a much-needed update. Once implemented in TNM, this new REMEL database would be used by all state DOTs for noise analysis on federal aid highway projects. In addition, existing noise simulation software like SoundPlan is sophisticated and flexible enough to accommodate REMEL data. A SoundPlan noise analysis using the updated REMEL database could then be used to develop acoustic design guidance for earthen berms and short concrete safety barriers. The REMEL data should be made available in an open-source or spreadsheet format, so that other acoustic researchers and engineers could access it and perform their own acoustic analysis for certain scenarios. For example, Caltrans has used the acoustic spectral data from the NCHRP 25-49 Roadway Construction Noise Model database to estimate construction noise impacts on nearby sea lion beach-haul-out habitat.

State DOTs are already examining noise reducing alternatives from shorter noise barriers like earthen berms and concrete safety barriers on elevated roadways. Caltrans is mapping corridor-long pavement acoustics and its impact on roadside noise levels. This REMEL update research could help support some of this on-going noise-reduction design work.

The AASHTO Noise Work Group has discussed the importance of this issue at length and strongly supports this research. CALTRANS has pioneered the practice of OBSI and can provide technical support for that part of the effort.

Sponsoring Committee:AEP80, Transportation-Related Noise and Vibration
Research Period:24 - 36 months
Research Priority:High
RNS Developer:Bruce Rymer, P.E.
Date Posted:01/11/2021
Date Modified:01/25/2021
Index Terms:Pollutants, Databases, Traffic noise, Acoustics, Sound transmission,
Cosponsoring Committees: 
Data and Information Technology

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