Skip to Main Content
U.S. Forest Service
Caring for the land and serving people

United States Department of Agriculture

Home > Search > Publication Information

  1. Share via EmailShare on FacebookShare on LinkedInShare on Twitter
    Dislike this pubLike this pub


    Forest road aggregate changes due to traffic. The physical processes that cause these aggregate changes need to be understood for more effective road management that can help reduce maintenance costs and efforts, and negative environmental impacts of forest roads. This study modeled three processes that could change the particle size distribution (PSD) of forest road aggregate: crushing (breaking down the surfacing material), subgrade mixing (moving upward of fine-grained, roadbed sediment), and sweeping (migration of loose aggregate particles to the shoulder and roadside by tire action). There are two types of sweeping: sweeping-out (dislodging large-size particles from tire tracks) and sweeping-in (accumulating large-size particles near the roadside and shoulder). Our study modeled the expected traffic-induced processes based on theoretical concepts and literature to examine how these processes change forest road aggregate PSD. Then the modeled results were compared with the observed PSDs from cross-sectional locations where traffic-induced processes likely occurred. Based on these comparisons, we enhanced the modeling and inferred how much the crushing, subgrade mixing, and sweeping-in processes changed the PSDs, but could not infer the sweeping-out process due to the difficulty in separating the sweeping-out from crushing. This study demonstrates that the traffic-induced processes could be modeled and quantified using the following assumptions: crushing was estimated by assuming a half logarithmic normal distribution with a mean of the crushed particle diameter and higher crushing rates for large-size particles; subgrade mixing was estimated by assuming the move-in of fine-grained subgrade soils from the road bed; and sweeping-in was estimated by assuming the move-in of large-size particles with a logarithmic normal distribution. Our modeling approach can offer insights on how traffic-induced processes affect road aggregate under various road and traffic conditions. This information can be useful in developing cost-effective road maintenance strategies and implementation plans.

    Publication Notes

    • You may send email to to request a hard copy of this publication.
    • (Please specify exactly which publication you are requesting and your mailing address.)
    • We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
    • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.


    Rhee, Hakjun; Fridley, James; Chung, Woodam; Page-Dumroese, Deborah. 2019. An approach for modeling and quantifying traffic-induced processes and changes in forest road aggregate particle-size distributions. Forests. 10: 769.


    Google Scholar


    crushing, logarithmic normal distribution, particle size distribution, process modeling, road aggregate, subgrade mixing, sweeping, traffic

    Related Search

    XML: View XML
Show More
Show Fewer
Jump to Top of Page