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    <title>Research in Progress (RIP)</title>
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    <atom:link href="https://rip.trb.org/Record/RSS?s=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" rel="self" type="application/rss+xml" />
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    <copyright>Copyright © 2026. National Academy of Sciences. All rights reserved.</copyright>
    <docs>http://blogs.law.harvard.edu/tech/rss</docs>
    <managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor>
    <webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster>
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      <title>Research in Progress (RIP)</title>
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      <link>https://rip.trb.org/</link>
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    <item>
      <title>Development of In-Pavement LFBG Sensors for Vehicle WIM System Measurement and Monitoring in Rural Low-Volume Road Conditions Phase One: Theoretical Research</title>
      <link>https://rip.trb.org/View/2596477</link>
      <description><![CDATA[The research aims to address the growing challenge of accurately monitoring overweight truck loads on low-volume roads, which present unique issues for both infrastructure durability and road safety. Low-volume roads, defined as those carrying fewer than 2000 vehicle per day (and often fewer than 400 vehicles per day in rural areas), account for over 80% of the roads in North Dakota. Given the state’s reliance on agriculture and natural resources transport, overload trucks frequently travel these roads, which are not designed to withstand the repeated stress of excessively heavy loads. While special permits are issued for trucks carrying heavy loads under specific conditions, enforcing weight limits on numerous low-volume roads remains a significant challenge. This issue compromises the longevity of the road infrastructure and poses safety risks for all road users. Therefore, accurate monitoring and enforcement of weight limits on low-volume roads is crucial for maintaining infrastructure and enhancing road safety.]]></description>
      <pubDate>Mon, 08 Sep 2025 16:01:37 GMT</pubDate>
      <guid>https://rip.trb.org/View/2596477</guid>
    </item>
    <item>
      <title>Evaluating and Implementing Ground Penetrating Radar (GPR) for Continuous and Rapid Monitoring of Moisture Fluctuations in In-Service Roads</title>
      <link>https://rip.trb.org/View/2487309</link>
      <description><![CDATA[Traditional methods for measuring pavement moisture, including in-place sensors and indirect assessments like FWD, can be costly, invasive, slow, offer limited spatial coverage, and disrupt traffic. In contrast, ground penetrating radar (GPR) offers a non-invasive, portable solution for swiftly evaluating extensive road segments, detecting subsurface moisture levels with reasonable cost, thereby supporting local road authorities in promptly assessing moisture conditions in critical pavement areas. The aim of this research study is to advance the validation and implementation of GPR-based pavement moisture assessments on actual low-volume roads.]]></description>
      <pubDate>Fri, 18 Jul 2025 09:49:56 GMT</pubDate>
      <guid>https://rip.trb.org/View/2487309</guid>
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    <item>
      <title>Development of Crushed Quarry Aggregate Surfacing Specifications </title>
      <link>https://rip.trb.org/View/2533742</link>
      <description><![CDATA[South Dakota’s transportation system includes over 83,000 miles of roads of which about ten percent are state-controlled, and three percent are federal routes. The remaining 72,000 miles are mostly low-volume roads (LVR).  A LVR is defined as a road that carries less than 400 vehicles per day. Typically, these roads fall under the jurisdiction of counties, townships, and municipalities. LVRs play an important role in the State’s economy by providing essential links not only between rural areas but also between rural and urban areas. A significant portion of LVRs in South Dakota are gravel. While South Dakota local governments are not bound by the State’s gravel surfacing specification, survey results from the SD2009-08 study entitled Gravel Surfacing Guidelines for South Dakota, revealed the majority of local government respondents use the State Gravel Surfacing specification. For some areas of the state, there is a shortage of “natural” gravel that will meet the Gravel Surfacing specification as per the 2015 SDDOT Standard Specifications for Roads and Bridges.  This is due to the drying up of the state's “natural” gravel pits, which will only get worse over time. In addition to gravel supply concerns, rising costs and tightening budgets have encouraged local governments to consider and construct roads with alternate aggregate materials under a range of specifications. These include SDDOT Base Course specifications, local specifications, or no specifications at all. Local governments, in areas having nearby quarries, have installed aggregate surfacing using crushed quarry aggregate, which is defined as crushed limestone, quartzite, or granite. According to the local owners and SD Local Transportation Assistance Program (LTAP) personnel, several of these surfaces perform similarly to “natural” gravel surfacing. The fines in the material appear to have a binding quality that creates a firm roadway surface. Unfortunately, the criteria for defining a well-performing crushed quarry aggregate surfacing and the specifications associated with that performance have never been established.  Currently, the only way to duplicate a well-performing crushed quarry aggregate surfacing is through trial and error. Through the development of criteria defining a well-performing aggregate surface and the establishment of the associated specific requirements for crushed quarry material, owners would be provided an alternative option to “natural” gravel surfacing that is readily duplicated and available.]]></description>
      <pubDate>Tue, 01 Apr 2025 08:39:01 GMT</pubDate>
      <guid>https://rip.trb.org/View/2533742</guid>
    </item>
    <item>
      <title>Synthesis of Information Related to Highway Practices. Topic 56-20. Pavement Design and Evaluation of Low Volume Roads with Heavy Loads



</title>
      <link>https://rip.trb.org/View/2384708</link>
      <description><![CDATA[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 departments of transportation (DOT's) and the Federal Highway Administration (FHWA) have invested significant resources on 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 nonstandard axle-configurations) nor were they developed to provide designs for all types of LVRs. 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.

OBJECTIVE: The objective of this synthesis is to document current state DOT practice for the structural design and evaluation of paved and unimproved LVRs, particularly those exposed to heavy loads. ]]></description>
      <pubDate>Fri, 31 May 2024 20:08:56 GMT</pubDate>
      <guid>https://rip.trb.org/View/2384708</guid>
    </item>
    <item>
      <title>Network Screening on Low-Volume Roads: Empirical Validation of a New Proposed Methodology</title>
      <link>https://rip.trb.org/View/2170310</link>
      <description><![CDATA[Maintaining safety on the roadway system has become a top priority for most highway agencies in recent year because traffic crashes and associated casualties remain at alarming levels in the United States. However, tighter budgets require highway agencies to identify locations that are associated with higher crash risks (and often higher crash reductions) for optimum use of their limited resources. To this end, highway agencies systemically screen the network to identify sites that are expected to yield greater safety benefits, thus deserving more consideration for Highway Safety Improvement Program (HSIP) funds.

A recent project sponsored by the Montana Department of Transportation (MDT) and the Small Urban, Rural, and Tribal Center on Mobility (SURTCOM) developed a methodology for network screening that requires a minimal amount of geometric, traffic, and crash data. The method can be implemented by local agencies such as counties, reservations, and townships as it does not require extensive technical expertise. This method was primarily developed using the safety performance functions (SPFs) and crash modification factor (CMFs) contained in the Highway Safety Manual (HSM). Given the scope of the previous project, no validation was conducted to assess the robustness of the proposed method using field data. This validation is deemed very important to better understand the strengths and limitations of the proposed methodology especially since the HSM is a national document and does not necessarily represent the safety trends in any specific region within the country.]]></description>
      <pubDate>Fri, 12 May 2023 15:48:53 GMT</pubDate>
      <guid>https://rip.trb.org/View/2170310</guid>
    </item>
    <item>
      <title>2023 Technology Exchange on Low Volume Road Design, Construction and Maintenance</title>
      <link>https://rip.trb.org/View/1892166</link>
      <description><![CDATA[The primary activities of this pooled fund project are technology exchange, information sharing, and the facilitation of partnering relationships among state agencies and participating members with the Federal Highway Administration (FHWA), Local Public Agencies and other appropriate agencies and associations. Technology exchange activities in conjunction with the 13th International Conference on Low Volume Roads will be advantageous to participating members. Specifically, this pooled fund will: 1. Provide communication and information sharing among member participants: Discuss research, development and technology transfer needs in the areas of design, construction, maintenance, and safety on low volume roads and provide research ideas to the Transportation Research Board (TRB) in the areas of Low Volume Roads. 2. Member workshop at the 13th International Conference on Low Volume Roads: Provide a technology and knowledge exchange forum to enhance the practical knowledge of pooled fund participants concerning low volume road management with a focus on encouraging State DOT and other agency participation in the pooled fund. 3. Pooled Fund Member Meeting on Low Volume Road Issues: Provide a technology and knowledge exchange forum focused on Low Volume Road issues. Topics may include agency collaboration, funding, asset management, shared right of way (ROW)/utilities, safety programs, emergency response, training and certifications, maintenance of traffic, federal oversight, standards and specifications, contracting methods, environmental issues, energy development, maintenance, material sources and quality, and bonding. 4. Technology Transfer through paper publication, webinars, technology field demonstrations, and expanding access to solutions on issues selected by pooled fund member in areas of Low Volume Road Design, Construction and Management.]]></description>
      <pubDate>Mon, 15 Nov 2021 19:01:46 GMT</pubDate>
      <guid>https://rip.trb.org/View/1892166</guid>
    </item>
    <item>
      <title>Optimizing the Performance of Item 404-Low Volume Traffic Mixes</title>
      <link>https://rip.trb.org/View/1875934</link>
      <description><![CDATA[Item 404-Low Volume Traffic (LVT) is an asphalt surface course recipe specification that was developed for use in low volume traffic applications by Flexible Pavements of Ohio (FPO). Item 404-LVT is a mix that is rich in asphalt binder, fine textured, nonrestrictive in aggregate shape and type, with restrictive RAP limits. It can be placed in a thin layer of 1 inch for economy. While the Ohio Depart of Transportation (ODOT) abandoned the use of its Item 404 specification in 2002, various local public agencies (LPAs) throughout Ohio continued to use FPO's 404-LVT on roads with very low truck volumes. The predominate destructive stresses on many local roadways is caused by long-term cracking from environmental factors, as opposed to heavy truck traffic. Much of the information related to the overall performance, longevity and cost effectiveness of mixes from the 404-LVT are based on previous experience of local engineers. Some local engineers utilize mixes from this specification almost exclusively, while others opt to use different mix designs, such as those from ODOT 448 specifications. LPAs that utilize mixes the 404-LVT specification are generally satisfied with its performance, however, it is recognized that the specification could be improved.  

The goal of this research is to optimize the 404-LVT specification utilized by Ohio's local public agencies. This research will identify opportunities to make simple changes to the 404-LVT specification so it is more cost effective without adversely impacting its performance. Results from this research will provide local transportation professionals with a better understanding of and more confidence in the performance of the 404-LVT mix design. An optimized 404-LVT specification may lead to long-term crack resistant, cost effective, longer-lasting, pavements for low volume roads where the primary stresses are from environmental conditions.          ]]></description>
      <pubDate>Wed, 01 Sep 2021 11:01:18 GMT</pubDate>
      <guid>https://rip.trb.org/View/1875934</guid>
    </item>
    <item>
      <title>Developing a Methodology for Implementing Safety Improvements on Low-Volume Roads in MT</title>
      <link>https://rip.trb.org/View/1752451</link>
      <description><![CDATA[Maintaining safety on the highway system has been a top priority for most highway agencies in the US given the heavy toll in deaths and casualties associated with traffic crashes. The limited funds available to highway agencies for safety improvements require careful consideration of sites that are more promising in improving safety at the network level. Therefore, highway agencies systemically screen the network to identify those sites that are expected to yield greater safety benefits, thus deserving more consideration for safety improvement funds. While this process has been successfully implemented by many agencies for urban and major rural highways, it may prove difficult on rural low-volume roads including local county roads. The low traffic exposure on these roads and consequently the low number of crashes occurring may preclude the possibility of using crash data alone in identifying and ranking candidate sites for safety improvement projects. The proposed research attempts to address this issue by providing a much-needed guidance to help in systemically identifying and ranking sites deserving safety treatments on local low-volume roads.]]></description>
      <pubDate>Thu, 19 Nov 2020 14:25:36 GMT</pubDate>
      <guid>https://rip.trb.org/View/1752451</guid>
    </item>
    <item>
      <title>Taconite as a Lower Cost Alternative High Friction Surface Treatment to Calcined Bauxite for Low Volume Roads in Minnesota</title>
      <link>https://rip.trb.org/View/1678052</link>
      <description><![CDATA[This study will evaluate whether Mesabi (taconite) friction aggregate can partially or fully replace calcined bauxite in high friction surface treatment applications by considering appropriate treatment installation alternatives, including but not limited to: (1) Various adhesion methods, such as epoxy, asphalt binder, and micro surfacing; (2) Varying blends of Mesabi friction aggregate and calcined bauxite including 100% Mesabi friction aggregate and 100% calcined bauxite (for comparison); and (3) Appropriate aggregate gradation.]]></description>
      <pubDate>Thu, 09 Jan 2020 14:30:11 GMT</pubDate>
      <guid>https://rip.trb.org/View/1678052</guid>
    </item>
    <item>
      <title>Asphalt Mix Overlay Alternative for Low Volume Roads on the Local Transportation System
</title>
      <link>https://rip.trb.org/View/1530886</link>
      <description><![CDATA[Many local governments are faced with low volume roads in need of repairs due to fatigue cracking.  Currently, there are relatively few known economical solutions from which to choose.  Options range from costly full-depth reclamation to chip sealing.  Some county engineers have tried other techniques to address this issue with varying degrees of success.  Some local agencies, such as Medina and Muskingum County, have used a cold-laid, motor paver mix followed by a chip seal surface.  While these counties have seen some positive results to this technique, the motor paver equipment is not widely available in Ohio and, for some local public agencies, can be expensive.  An option of a hot-mix that matches the performance of the motor paver mix that can be placed by hot mix paving contractors could make this treatment option more widely available to local agencies throughout Ohio.

While some transportation professionals believe the solution to this issue is in the application method, others question if the mix being used is more of a contributing factor.  ODOT has a supplemental specification (#823) that provides guidance for producing a light traffic asphalt mixture.  However, its direct application to local roads may not be appropriate.  Factors such as variations in traffic volume, traffic type and traffic patterns may influence the performance of this asphalt mixture resulting in the ODOT specification being over designed for the needs of the local road.  For example, SS 823 indicates that is it is designed for locations with less than 50 trucks per day.  In some rural Ohio counties, it is highly possible to have less than 50 trucks per year.  Given that high traffic volume for some county and township roads can be significantly less than what ODOT considers to be a low volume road, the impact weather has on the pavement can be more damaging to the road surface than the traffic.  Some county engineers have tried in-house developed mixes and have had varying degrees of success.

This research will be conducted in two phases. The goal of Phase 1 is to conduct an in depth practice analysis aimed at identifying existing research, best practices of Ohio's local government agencies, and opportunities from other states and based on state of practices, develop a laboratory testing protocol of mix design procedures.  Phase 2 will perform in-field evaluation of the mix design procedures identified in Phase 1 and is contingent upon the successful completion of Phase 1 and the written authorization of the ODOT Research Section.
]]></description>
      <pubDate>Wed, 08 Aug 2018 13:46:00 GMT</pubDate>
      <guid>https://rip.trb.org/View/1530886</guid>
    </item>
    <item>
      <title>Holding Strategies for Low Volume State Routes - Phase II</title>
      <link>https://rip.trb.org/View/1489763</link>
      <description><![CDATA[The objective of the proposed research project is to assist Iowa Department of Transportation (Iowa DOT) in developing strategies for maintaining lower volume highways that are near the end of their service life to a satisfactory level in order to delay the larger expense of rehabilitating or reconstructing them. A technical advisory committee (TAC) will be established to assist Iowa State University in its efforts to execute this research project including representation from the Iowa DOT, local agencies (county and/or city) and industry. The tasks for this proposal are outlined below. The level of effort for each task will be determined in consultation with the chair and other members of the TAC. The total effort will remain within the scope of the budget unless authorized in advance by the Iowa DOT. The intention is to provide flexibility to meet unforeseen challenges and to take advantage of unexpected opportunities. Researchers will collaborate with the TAC and designated Iowa DOT personnel to design and execute a holding strategy construction project for an Iowa roadway. Within this construction project, a series of test sections and a control section will be placed. The plan for the test sections will be developed to be appropriate for the local condition for the roadway and the construction budget that the Iowa DOT has available to accomplish the project. A combination of Iowa State University and Iowa DOT resources will be used to accomplish the objective. This scope of work provides for two sets of test section post-construction observations after construction is complete. Since experimentation with holding strategies is expected to be an ongoing effort, it is assumed that further post-construction observations may be funded as part of subsequent research projects. Monitoring of the Iowa 93 test section will also continue in this phase of the project. (Task 1) Literature Review and interviews. The research team will conduct a complete review of published literature including academic journals, international journals, trade publications, product literature and Internet web pages. It is expected that the search will initially identify many articles on preventive maintenance and pavement preservation which may be somewhat related to this topic, but are not on target. Since the research team has considerable experience on those other topics, it will be possible to quickly remove those from consideration and focus on literature involving holding strategies. The literature review for this phase of the research will build on previous literature reviews that were conducted for the first phase of the project. This will reduce the effort required for this task making additional effort available for other tasks. (Task 2) Pre-design Investigation. A pre-design investigation will be conducted to ensure that the test sections for holding strategies are appropriate for the local circumstances. The investigation will commence by interviewing district maintenance personnel and reviewing maintenance and construction records for the selected roadway. In addition, current information from the Mile Post Test Section Book will be reviewed and output from the biannual pavement management data collection effort will be reviewed. Included in the biannual data collection is the IRI (international roughness index) for each wheel path, longitudinal and transverse cracking, alligator cracking, and rutting. 'FWD (falling weight deflectometer) data is collected on a six year rotation. After this review has been accomplished, an additional effort will be launched to provide information that was not available from the previous sources, if necessary. That additional effort might include: Cores to assess current pavement and base section characteristics; Geo-technical characterization of the sub-grade such as using the dynamic cone penetrometer; and FWD testing if FWD tests have not been conducted within the last two years. All of the above will, if needed, be provided by the Iowa DOT. The results of this testing program will be reviewed, and feasible holding strategy concepts will be selected for possible inclusion in the test sections. (Task 3) Test Section Design. An experimental design to compare holding strategies will be developed to fit within the Iowa DOT budget and the circumstances documented in the predesign investigation. Constructability of the test sections will also be considered. It is expected that four to six test sections plus a control section will be designed. The design for the control section will reflect the current treatment that the Iowa DOT would typically use for a road that exhibits similar preconstruction conditions to that of the roadway selected for this project. It is expected that the test sections will be a combination of seal coats, cold in-place recycling, hot in place recycling, inter layers and other applications such as surface treatments and HMA overlays as appropriate. After the design is developed, the Iowa DOT will create contract documents and procure construction services through the Iowa DOT letting process. (Task 4) Test Section Construction. The test section construction will be executed in accordance with the contract documents developed in Task 3. Researchers will update the preconstruction surface distress survey immediately before construction and observe critical processes of construction to the extent possible within the budget and provide technical support. The Iowa DOT will provide its usual construction management services. (Task 5) Post Construction Monitoring. Post construction monitoring efforts will include: Photographs, a surface distress survey, roughness measurements, coring to assess the condition of recycled layers, and FWD testing. These efforts will be arranged to focus on documenting critical changes in performance and will continue for one season after construction is accomplished. Continued monitoring of the Iowa 93 test sections will continue in this task too. (Task 6) Data Synthesis. The research team will review the documentation that was generated from previous tasks and develop an initial assessment of the success of each strategy. The assessment process will include practical concerns such as ease of material selection, design and specification development, constructability, cost and schedule. Longer term assessments could be provided with subsequent phases of this research project. (Task 7) In-house and Contracted Effort. Based on knowledge obtained in the previous tasks, especially Task 1 - Literature Review and Interviews, an analysis will be conducted. This analysis will be included in the final report. (Task 8) Final Report. A final report will be developed that describes the investigation and provides conclusions and recommendations, based on the observations that have been conducted up to the time of writing.]]></description>
      <pubDate>Mon, 27 Nov 2017 10:51:00 GMT</pubDate>
      <guid>https://rip.trb.org/View/1489763</guid>
    </item>
    <item>
      <title>Development of Rural Road Bridge Weigh-in-Motion System to Assess Weight and Configuration of Farm to Market Vehicles</title>
      <link>https://rip.trb.org/View/1350447</link>
      <description><![CDATA[The weights and configurations of large vehicles traveling the primary interstate system are known with relative certainty due to the information collected at numerous weigh stations. It is uncommon, however, that farm-to-market vehicles and other implements of husbandry (IoH) travel the interstate system; thus, an accurate assessment of the characteristics of these vehicles is left unknown. Since these vehicles commonly travel rural roads, and often at weights exceeding the legal limit especially during harvest, an accurate understanding of low-volume road usage is necessary to properly plan for the near-term repair and replacement of structures and roadways; even more, the information collected will help improve the long-term performance and asset management activities. 

A recently completed pooled-fund project, which the Iowa Department of Transportation (DOT) was the lead state on, looked to assess the impact of implements of husbandry on bridges. Those efforts produced valuable information especially as it relates to lateral load distribution. Even so, the project was largely completed using a database of virtual vehicles developed through information provided by equipment manufacturers and rule-of-thumb. Although it is believed the database generally represented current vehicles, the accuracy cannot be verified without direct measurement of all vehicles. Furthermore, one piece of missing information is the frequency with which those vehicles cross low-volume road bridges. 

The objective of this project was to develop a portable weigh-in-motion system using a rural road bridge to estimate the characteristics of vehicles traveling these roads. A unique instrumentation setup was utilized with strain gages placed on the bottom face of the deck as well as on the top and bottom flanges of the girders, which allowed for the application of algorithms for vehicle classification determination. Further classification of the IoH vehicles is made possible by actual determination of specific vehicle type based on strain response and the corresponding number and spacing of axles. This vehicle information provides actual loading and corresponding bridge response and, thus, maintenance decisions and actual structural demands can be properly selected based on existing traffic types and frequencies. The system developed for this project can be deployed on rural bridges for realistic traffic classifications. 
]]></description>
      <pubDate>Wed, 15 Apr 2015 01:01:21 GMT</pubDate>
      <guid>https://rip.trb.org/View/1350447</guid>
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