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Low-Volume Road Engineering

The following article was published in the Fall 2019 edition of the Ohio Asphalt magazine and is presented here courtesy of Flexible Pavements of Ohio. There are several references to Ohio Department of Transportation specifications and mix classifications; however, the information and basic concepts are applicable across the United States.


A recent National Center for Asphalt Technology (NCAT) report (NCAT Report 19-04) should be of interest to engineers responsible for low-traffic volume roads (LVRs).

The report, "A Synthesis of Technical Needs of Asphalt Pavements for Local Roads,” provides guidance on many of the challenges in the design, construction and management of LVRs. The report confirms that the needs for LVRs, especially asphalt concrete materials, are quite different from high-traffic highways and are not well served by the usual state specification materials intended for those heavy-traffic highways. The report identifies the need for simple guides for these issues and especially for materials for LVRs.

For design of overlays and rehabilitation or LVRs pavements, the report recommends using PAVEXpress, a free online design tool that can be accessed through the FPO website at

Among the report’s recommendations for asphalt concrete materials are:

• Higher percentages of natural sands may permit more economical and workable mixes

• Aggregate gradation ranges should be limited to smaller maximum particle sizes to aid compaction and to improve resistance to water intrusion

• Binder grade should be selected based on climate and not for traffic considerations

• Volumetric mix design criteria should be adjusted to achieve higher asphalt contents for improved compact ability, lower permeability and improved cracking resistance

The 37-page NCAT report can be downloaded at

Fortunately, in Ohio, many of these issues have been or are being addressed. Asphalt concrete material specifications have been developed and are being used to improve surface performance on LVRs. Research has and continues to take place to confirm design parameters and materials specifications for LVRs through the Ohio's Research Initiative for Locals (ORIL) research program.

Flexible Pavements of Ohio (FPO) has developed asphalt concrete specifications specifically for use on LVRs and Technical Bulletins have been created that describe their appropriate use. Technical Bulletins and specifications for 404LVT and Thinlay Asphalt concrete can be found on the FPO Technical Resources website at

In addition, an ORIL research project (SJN 134991) conducted by Ohio University identified appropriate AASHTO 93 design layer coefficients, which can be used with PAVEXpress for various reclaimed materials commonly used in the rehabilitation of LVRs. This report was summarized in the Summer 2016 edition of Ohio Asphalt, which can be found at The full report can be found on the ORIL website:

So, if you are an engineer responsible for LVRs, we recommend that you read the NCAT report and use the asphalt concrete materials specifically available for LVRs to achieve project success and improve the performance of your low-volume pavements.

You may learn more about Flexible Pavements of Ohio by visiting

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