Preliminary Scope

Low-volume road (LVR) networks function as the primary link to highway transportation systems as well as the connection of communities. The structural capacity of LVRs plays a vital role in providing competent, stable, and durable roads. While state DOTs and FHWA have invested significant resources in improving the structural design of high-volume pavements, the structural design of LVRs, particularly local access roads in rural areas, often goes overlooked. LVRs built following a template design or minimum local standards may be sufficient for passenger vehicles, but once LVRs are subjected to heavy traffic from agriculture, renewable and non-renewable energy development, or logging operations, the structural capacity of LVRs is compromised and severe damage occurs. The damage from heavy loads can be further exacerbated by seasonal impacts such as spring thaw.

When designing pavements for LVRs, many LVR owners and managers follow the AASHTO design guide, which converts axle loads into equivalent single-axle loads (ESALs) by using load equivalency factors (LEFs). However, these design practices may not adequately account for heavy loads (i.e., overweight standard trucks and non-standard axle-configurations) nor were they developed to provide designs for all types of LVRs (i.e., paved, unpaved, and unimproved types). LVRs that experience a high percentage of heavy standard trucks and overweight non-standard traffic and commensurately high loads suffer rapid and premature road deterioration. Such failures are often attributed to overweight loads applied to a substandard road design. To address such failures, it is crucial to improve the structural design of LVRs carrying overweight loads (i.e., apply factors to ensure a more robust pavement structure).

The objective of this synthesis is to document current state DOT practice for the structural design of LVRs (i.e., paved, unpaved, and unimproved types), particularly those exposed to heavy loads. The synthesis will also identify opportunities for future research to modify current evaluation methods and design standards to provide LVR networks that can effectively accommodate heavy loads and prevent premature structural failure.

Information to be gathered includes (but is not limited to):

·       Typical structural design of LVRs;

·       Definition of heavy loads for LVRs;

·       Common types of overweight trucks and non-standard heavy traffic;

·       Overload permitting process;

·       Design modifications for LVRs supporting heavy loads, including what and where heavy loads are used in the United States;

·       The impacts of heavy loads on the structural capacity of LVRs;

·       Common effects of heavy loads on LVRs and the primary causes of structural failure of overloaded pavement sections;

·       Modifications to structural design of LVRs to accommodate heavy loads; and

·       The role and impact of spring-time load restrictions on LVRs.

An extensive literature review and a survey of state DOT’s will be conducted to gather information on the synthesis topic. Follow-up interviews will be carried out with selected state DOTs.

Information gathered will be used to identify examples of LVRs supporting heavy loads and document associated modifications to structural designs, if applicable. Information gaps and suggestions for research to address gaps in structural design and evaluation of LVRs supporting heavy loads will be identified and reported.

Information Sources (Partial)

• Coghlan, G. T. (2000). Opportunities for Low-Volume Roads. Transportation Research Board CD.
• Sebaaly, P. E., Siddharthan, R., and Huft, D. (2003). “Impact of Heavy Vehicles On Low-Volume Roads.” Transportation Research Record 1819(1), 228-235.
• Wilde, W.J. (2014) “Assessing the effects of heavy vehicles on local roadways.” MnDOT, 2014-32.

TRB Staff
Dr. Zhiye Li
Email: Zli@nas.edu

Meeting Dates
First Panel Meeting: TBD (Virtual via Microsoft Teams)
Teleconference with Consultant: TBD
Second Panel Meeting: TBD (Virtual via Microsoft Teams)