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    <title>Transport Research International Documentation (TRID)</title>
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    <copyright>Copyright © 2026. National Academy of Sciences. All rights reserved.</copyright>
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    <managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor>
    <webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster>
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      <title>Transport Research International Documentation (TRID)</title>
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      <title>Demonstrating the Use of Small Uncrewed Aircraft Systems (Drones) Capabilities and Data for Iowa Transportation and Infrastructure Work: Pilot Project No. 3 – Use of Small Uncrewed Aircraft Systems for Erosion and Sediment Control Device Monitoring</title>
      <link>https://trid.trb.org/View/2711929</link>
      <description><![CDATA[Erosion and sediment control devices (ESCDs) are commonly installed on construction projects to mitigate the effects of runoff and sediment transport in downstream environments. Regulatory agencies such as the U.S. Environmental Protection Agency require these devices to be frequently inspected and maintained promptly when deficiencies are observed or when extreme upcoming precipitation events are expected. Smaller construction sites (less than 0.1 hectares) typically have fewer ESCDs, enabling effective routine field inspections. However, performing similar field inspections on larger construction sites is considerably more challenging due to their spatial distribution and the variety of ESCDs deployed across these sites. Other challenges include difficulty in physically locating these ESCDs due to complex or unstable terrain, potential exposure of inspection personnel to hazardous substances, and the significant amount of time required to navigate large sites and conduct detailed inspections. To address these limitations, this study investigated the use of small uncrewed aerial systems (sUAS) as a remote sensing platform for ESCD inspection and monitoring. The objective of this study was to develop a rapid data collection and processing pipeline that enables inspection personnel to efficiently evaluate site conditions and ESCD performance, supporting timely, informed decision-making. We deployed multiple sUAS platforms capable of producing high-resolution orthophotos for remote visual inspection and multispectral data for further analysis. These analyses included estimating vegetation growth on sloped terrain and quantifying the sediment accumulated near barriers such as silt fences and check dams. Digital elevation models (DEM) derived from the processed sUAS data also offered valuable insights into surface topography and flow patterns, enabling assessment of upstream and downstream conditions and improving understanding of how effectively ESCDs are functioning through quantitative analysis.]]></description>
      <pubDate>Fri, 12 Jun 2026 10:11:53 GMT</pubDate>
      <guid>https://trid.trb.org/View/2711929</guid>
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    <item>
      <title>Local Roads Research Forum under TPF-5(495) 2023 Technology Exchange on Low Volume Road Design, Construction and Maintenance</title>
      <link>https://trid.trb.org/View/2709437</link>
      <description><![CDATA[The 2023 Technology Exchange on Low Volume Road Design, Construction and Maintenance pooled fund (TPF-5(495)) hosted a Local Roads Research Forum on March 3 and 4, 2026, with the Iowa Department of Transportation coordinating as lead state in partnership with the Iowa County Engineers Association Service Bureau. The purpose of this forum was to help participants understand each another's needs and challenges related to local roads research. The forum focused on four broad areas: Current state DOT local roads research, round table discussions on hot topics, national perspectives, and future planning.]]></description>
      <pubDate>Thu, 11 Jun 2026 09:16:54 GMT</pubDate>
      <guid>https://trid.trb.org/View/2709437</guid>
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    <item>
      <title>Mid-Atlantic Peer Exchange on Balanced Mix Design (BMD): Outcomes Summary</title>
      <link>https://trid.trb.org/View/2691551</link>
      <description><![CDATA[Seven States from the Mid-Atlantic U.S. and the District of Columbia (the District) gathered for a peer exchange and discussion on implementation activities to support Balanced Mix Design (BMD). The peer exchange was sponsored by the Federal Highway Administration (FHWA). The seven States and the District met to assess the state-of-practice for the technology, tools, and techniques in designing, verifying, and accepting asphalt mixtures for different layers within the flexible pavement structure, as well as for overlays of different pavements following BMD emerging practices. The peer exchange was held in Washington, D.C. This summary report focuses on agency motivations for considering BMD, implementation challenges, key takeaways, and emerging themes. Participating States included: District Department of Transportation (DDOT), Iowa Department of Transportation (IDOT), Kentucky Transportation Cabinet (KYTC), Maryland DOT (MDOT), North Carolina DOT (NCDOT), South Carolina DOT (SCDOT), Virginia DOT (VDOT), and West Virginia DOT (WVDOT).]]></description>
      <pubDate>Mon, 20 Apr 2026 09:22:54 GMT</pubDate>
      <guid>https://trid.trb.org/View/2691551</guid>
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    <item>
      <title>Project Development and Utility Coordination as a Partnership</title>
      <link>https://trid.trb.org/View/2692374</link>
      <description><![CDATA[Utility relocation at the Iowa Department of Transportation (Iowa DOT) is frequently cited as a cause of construction delays and increased highway project costs. This research aimed to enhance alignment between the utility coordination and project development processes by providing recommendations for integrating utility stakeholder partnerships early in project development, with the broader goal of streamlining workflows to reduce utility-related delays and cost overruns. The recommendations presented in this report are designed to improve current utility data collection and utilization procedures and to foster a more cohesive approach that synchronizes project design with utility coordination efforts. To develop these recommendations, the research team collected data on utility coordination best practices from state, national, and international studies, followed by an assessment of the current Iowa DOT utility coordination approach. This assessment involved a content analysis of existing policies, guidance manuals, and technical documents and engagement with key stakeholders, including Iowa DOT staff, consultants, and utility companies. The findings identified areas for improvement that formed the basis for developing the Partnership Approach for utility coordination at the Iowa DOT. This proposed approach offers recommendations to improve the alignment of utility coordination with the project development process and incorporates best practices into the Iowa DOT’s utility coordination framework. The approach also proposes revisions to Iowa DOT guidance manuals and policies to incorporate these recommendations. The study findings and deliverables are anticipated to benefit key stakeholders in Iowa’s primary and local roadway projects by fostering a more collaborative and efficient process for managing utility impacts.]]></description>
      <pubDate>Fri, 17 Apr 2026 08:55:48 GMT</pubDate>
      <guid>https://trid.trb.org/View/2692374</guid>
    </item>
    <item>
      <title>Evaluating the Economic and Safety Trade-offs of Interchange and Access Drive Separation Distances
</title>
      <link>https://trid.trb.org/View/2627344</link>
      <description><![CDATA[The research project will evaluate whether the Iowa Department of Transportation’s (Iowa DOT) minimum separation standards between interchanges and first access points are overly restrictive and potentially detrimental to development opportunities around those interchanges. To achieve this, the project will utilize deep learning techniques to analyze high-resolution aerial photographs to identify interchanges on state-owned roadways, their first driveway access points, and the specific aspects of development status, such as the presence of commercial or residential buildings, vacant land, or agricultural use of the surrounding land. Crash data from the Iowa dataset will be examined to assess safety outcomes about these separation distances. A critical part of the analysis will involve evaluating the economic potential of these lands and estimating the impact of separation standards on land utilization and potential economic growth. 
In addition to state-owned interchanges, the study will identify non-interchange intersections with roadways with similar AADT levels, the number of lanes, if a median is present, and other relevant geometric features to access management. The closest access point will be determined for these intersections, mirroring the approach taken with the interchanges. The crash history for these locations will be retrieved to compare the safety performance of interchanges and non-interchange intersections directly.
This analysis, focusing on interchange and access point separation distances, will help isolate the effect of these separation standards on safety and development, controlling for traffic volume and other features. By examining interchange and non-interchange sites under similar conditions, the research will determine if the minimum separation distances at interchanges are justified or could be adjusted to better balance safety with economic development, potentially informing future policy decisions. The research will also determine the amount of developable land that could be available should the standards be relaxed.
]]></description>
      <pubDate>Wed, 19 Nov 2025 14:36:56 GMT</pubDate>
      <guid>https://trid.trb.org/View/2627344</guid>
    </item>
    <item>
      <title>Evaluating Electrical Resistivity as a Procedure to Aid in Characterizing Subsurface Conditions</title>
      <link>https://trid.trb.org/View/2617012</link>
      <description><![CDATA[The Iowa DOT Soils Design section participated in the Demonstration Stage of the Advanced Geotechnical Exploration Methods (A-GaME) initiative. The A-GaME initiative sought to promote the use of advanced geotechnical methods as a means to reduce cost in subsurface investigation. One of the proven geophysical methods promoted is known as Electrical Resistivity (ER). In response to the A-Game Initiative, the IDOT Soils Design Section has investigated electrical resistivity (ER) as a novel technique to aid with subsurface investigation. Soils Design proposed to apply ER to evaluate if the technology could result in: (1) a reduced number of borings, (2) an enhanced understanding of subsurface conditions and site variability, (3) identification of depth to bedrock, and (4) overall reduction in geotechnical subsurface investigation costs.]]></description>
      <pubDate>Fri, 07 Nov 2025 11:36:21 GMT</pubDate>
      <guid>https://trid.trb.org/View/2617012</guid>
    </item>
    <item>
      <title>Iowa Highway Research Board: 2000–2024</title>
      <link>https://trid.trb.org/View/2608098</link>
      <description><![CDATA[The Iowa Highway Research Board (IHRB) is an advisory board responsible for assisting the Iowa Department of Transportation (DOT) and the state’s cities and counties in the development and continuation of an effective program of research and development in highway transportation. Board membership includes representatives of Iowa’s city and county government highway agencies, the Iowa DOT, and Iowa’s public universities. The IHRB was established in 1949 to provide guidance and oversight for the use of the primary, secondary, and municipal road research funds. Years later, the IHRB is still fulfilling that role, overseeing about 20 new projects each year involving transportation issues in Iowa. The value earned from this research is continually returned to Iowa taxpayers multifold through cost savings of innovations, improved safety, and the implementation of proactive technologies. Since its founding, one of the keys to the board’s success is the collaborative nature of the advisory group. Over the past 25 years, IHRB members have seen nearly 400 projects completed, with funds of around $60 million. The IHRB encourages submission of research ideas that consider all aspects of transportation and related infrastructure through research, innovation, implementation, and technology transfer efforts. The scope of this book covers IHRB research and advancements from 2000 to 2024 and highlights significant IHRB research projects during that time. The projects are divided into eight chapters (Rural Road Safety, Low-Volume Roads, Pavement Preservation, Concrete Pavements, Bridges, Standards and Specifications, Sustainability, and Innovative Projects), each demonstrating the impact and necessity of the IHRB and its contributions over the years.]]></description>
      <pubDate>Wed, 29 Oct 2025 16:36:23 GMT</pubDate>
      <guid>https://trid.trb.org/View/2608098</guid>
    </item>
    <item>
      <title>Standards Updates for Single Span Prefabricated Bridges — Technology Transfer Technical Brief</title>
      <link>https://trid.trb.org/View/2592792</link>
      <description><![CDATA[Standards for Single Span Prefabricated Bridges were developed by HDR for the Iowa Department of Transportation in 2016 for the use on the county road system. These standards incorporated single span precast or precast/pretensioned concrete box beams with span lengths ranging from 30-feet to 70-feet, clear roadway widths of 24-feet and 30-feet, and skews of 0°, 15° or 30°. Additionally, the standards provided both cast-in-place and precast abutment design options founded on steel H-piles. The standards were developed utilizing the MicroStation V8i CADD software. This current update to the standards successfully implements the conversion of the standards to the MicroStation CONNECT platform and addresses obstacles to some precast fabricators regarding the use of fully tensioned top strands. In addition, the update addresses performance issues identified in the early procurement contract regarding top flange cracking near the ends of the concrete box beams resulting from elimination of the fully stressed top strands.]]></description>
      <pubDate>Tue, 26 Aug 2025 11:53:49 GMT</pubDate>
      <guid>https://trid.trb.org/View/2592792</guid>
    </item>
    <item>
      <title>Impact of Pavement Friction on Traffic Safety, Phase I: Pavement Friction Evaluation</title>
      <link>https://trid.trb.org/View/2576287</link>
      <description><![CDATA[Pavement friction significantly contributes to roadway safety by providing the grip required for safe travel. The Iowa Department of Transportation (DOT) has long recognized the importance of evaluating pavement skid resistance and its impact on traffic safety. Several devices have been developed to measure skid resistance. The Iowa DOT currently uses the locked-wheel skid tester (LWST), which is well accepted across the United States and globally. Due to its relatively narrow speed range and limitations on curves and short, low-speed segments, various types of continuous friction measurement equipment (CFME) have been proposed as alternatives, including the GripTester and sideway-force coefficient routine investigation machine (SCRIM). A broader issue in friction measurement is repeatability and reliability under different operational conditions, with temperature, pavement wetting, and test speed affecting the correlation between different devices. This study aimed to evaluate candidate CFME technologies for their ability to measure pavement friction at different test speeds and in different operational conditions relative to the LWST currently available at the Iowa DOT. Promising CFME technologies were selected, and a testing program based on statistical procedures was designed to evaluate the devices’ suitability for pavement friction evaluation in relation to the friction demand and safety analysis. CFME and LWST testing was performed at three asphalt and three concrete pavement test segments at different speeds and using smooth and ribbed tires, and tests were repeated on different days to determine performance in different operational conditions. A dynamic friction tester (DFT) and laser texture scanner (LTS) were used to verify the correlation between the CFME and LWST and to investigate the impact of pavement texture on dry and wet skid resistance. The research resulted in guidance and recommendations for friction evaluation on different components of the network, including curves and low-speed segments. These outcomes represent a step toward a consistent procedure for both routine pavement friction evaluation at the network level and spot investigation for high-risk areas.]]></description>
      <pubDate>Wed, 06 Aug 2025 15:00:21 GMT</pubDate>
      <guid>https://trid.trb.org/View/2576287</guid>
    </item>
    <item>
      <title>Evaluation of Rock Check Dam Performance Using Large-Scale Testing Techniques</title>
      <link>https://trid.trb.org/View/2577220</link>
      <description><![CDATA[Conveyance channels are commonly used on highway construction projects to manage the flow of water through the project to downstream discharge points or stormwater detention practices. However, these channels can be at risk of erosion before stabilization due to high-velocity flows. A common erosion control practice in channels is a rock check dam, which aims to slow flow by forming impoundment upstream of installations. Based on common spacing guidance, if rock check dams do not impound to their full height, areas of the channel will still be subject to erosive flow conditions. Past research has indicated that a geotextile overlay or smaller choker stone is required to facilitate a full impoundment, particularly in low flow conditions. Despite the widespread use of rock check dams, very few standards include overlays or chokers or have been evaluated for performance. To evaluate the Iowa Department of Transportation (DOT) standard rock check dam installation and develop more efficient and cost effective modified installations, a standard Iowa DOT channel located at the Auburn University – Stormwater Research Facility was used. Installations were subjected to channelized flow conditions that represent those found on Iowa highway construction projects; measurements taken during testing include water depth, flow velocity, impoundment length, and dewatering time. The Iowa DOT standard installation facilitated 4.2 and 5.9 ft (1.3 and 1.8 m) of impoundment under the low (0.85 ft³ /s [0.024 m³ /s]) and high (1.7 ft³ /s [0.048 m³/s]), indicating that much of the test channel was subject to high velocity, erosive flows. Installation components such as the removal of the excavation beneath the installation, the use of a smaller rock gradation, the addition of a geotextile overlay, dewatering holes in the geotextile overlay, and reducing the width of the installation, were evaluated to determine the impact on performance and improvements from the standard. Adding a geotextile overlay and switching to a smaller rock gradation significantly increased impoundment length; the addition of dewatering holes in the geotextile overlay resulted in faster dewatering times while not otherwise adversely impacting performance. Additionally, removing the excavation beneath the standard rock check dam installation and reducing the width of the installation were not found to negatively impact performance while reducing the installation and material costs. A most feasible and effective installation (MFE-I) installed on grade with the Iowa DOT erosion stone, a geotextile overlay with dewatering holes, and a reduced width from 6 to 4 ft (1.8 to 1.2 m) increased impoundment lengths to 58.7 and 57.5 ft (17.9 and 17.5 m) under the low and high flow conditions, respectively. The increased impoundment formation also impacted performance under sediment-laden conditions, with the MFE-I capturing 72.4% of introduced sediment, while the Iowa DOT standard installation captured 9.4%. The addition of the geotextile overlay also impacted water quality performance, with the MFE-I having statistically significantly lower discharge turbidity than the standard installation.]]></description>
      <pubDate>Thu, 31 Jul 2025 13:57:35 GMT</pubDate>
      <guid>https://trid.trb.org/View/2577220</guid>
    </item>
    <item>
      <title>North Dakota Department of Transportation E-Ticketing Peer Exchange: EDC-6 Peer-To-Peer Exchanges</title>
      <link>https://trid.trb.org/View/2528398</link>
      <description><![CDATA[North Dakota Department of Transportation (NDDOT) has been engaging with stakeholders and plans to institutionalize e-Ticketing by 2026. However, several challenges to statewide adoption must be addressed: paying for e-Ticketing, communicating the business value of e-Ticketing to contractors and suppliers, overcoming internet connectivity issues, and determining the effective use cases for e-Ticketing. To get e-Ticketing right, NDDOT consulted State DOTs that have successfully adopted e-Ticketing through a peer-to-peer exchange. The Federal Highway Administration (FHWA) sponsored a day-and-a-half-long peer-to-peer exchange in Bismarck, North Dakota, on March 29 and 30, 2022. The meeting included two FHWA representatives; representatives from DOTs that had successfully implemented e-Ticketing (i.e., the lead agencies)— Indiana (INDOT), Iowa (IOWADOT), Minnesota (MNDOT), and North Carolina (NCDOT); two subject matter experts from the EDC contractor’s team; and participants from NDDOT and the local construction industry. NDDOT served as the host agency and provided meeting room facilities. The meeting included a combination of presentations, panel discussions, questions and answers, and a participant survey.]]></description>
      <pubDate>Fri, 04 Apr 2025 16:18:15 GMT</pubDate>
      <guid>https://trid.trb.org/View/2528398</guid>
    </item>
    <item>
      <title>Virginia Department of Transportation E-Ticketing Peer Exchange: EDC-6 Peer-To-Peer Exchanges</title>
      <link>https://trid.trb.org/View/2528400</link>
      <description><![CDATA[Virginia Department of Transportation (VDOT) has developed a vision, established goals, and created an implementation plan for e-Ticketing. To further refine the approach to implementation, VDOT consulted state departments of transportation (DOT) that have successfully adopted e-Ticketing through a peer-to-peer exchange. The Federal Highway Administration (FHWA) sponsored a day-and-a-half-long peer-to-peer exchange in Richmond, Virginia, on November 1 and 2, 2022. The meeting included the following representatives from FHWA and state DOTs that had successfully implemented e-Ticketing (i.e., the lead agencies): Delaware (DelDOT), Iowa (IOWADOT), and Pennsylvania (PennDOT); three subject matter experts from the EDC contractor’s team; and participants from VDOT and the local construction industry. VDOT was the host and provided meeting rooms. The meeting included presentations, panel discussions, question and answer sessions, and a participant survey.]]></description>
      <pubDate>Fri, 04 Apr 2025 16:18:15 GMT</pubDate>
      <guid>https://trid.trb.org/View/2528400</guid>
    </item>
    <item>
      <title>Washington Department of Transportation E-Ticketing Peer Exchange: EDC-6 Peer-To-Peer Exchanges</title>
      <link>https://trid.trb.org/View/2528401</link>
      <description><![CDATA[Washington State Department of Transportation (WSDOT) is planning to procure a Web portal solution for e-Ticketing that would receive tickets electronically from any pre-authorized contractors and material producers regardless of their business size, share of DOT work, or the fleet management solutions they use. Furthermore, over the last four years, WSDOT has been successfully implementing numerous applications in the Oracle® UnifierTM cloud- based enterprise platform to automate business processes across various phases of a project’s lifecycle. As WSDOT seeks to deploy the e-Ticketing portal solution for bituminous, ready-mix concrete and aggregates, the agency intends to achieve a goal of “collect once, use many times.” To implement e-Ticketing successfully, WSDOT consulted state DOTs that have successfully adopted e-Ticketing through a peer-to-peer exchange. The Federal Highway Administration (FHWA) sponsored a day-and-a- half-long peer-to-peer exchange in Vancouver, Washington, on January 24 and 25, 2023. The meeting included an FHWA representative; representatives from DOTs who had successfully implemented e-Ticketing (i.e., the lead agencies)—Delaware (DelDOT), Georgia (GDOT), Iowa (IOWADOT), and Pennsylvania (PennDOT); two subject matter experts from the EDC contractor’s team; and participants from WSDOT and the local construction industry. WSDOT hosted the event and provided meeting room facilities. The meeting included a combination of presentations, panel discussions, questions and answers, and a participant survey.]]></description>
      <pubDate>Fri, 04 Apr 2025 16:18:15 GMT</pubDate>
      <guid>https://trid.trb.org/View/2528401</guid>
    </item>
    <item>
      <title>Development of Quality Standards for Inclusion of High Recycled Asphalt Pavement Content in Asphalt Mixtures – Phase IV</title>
      <link>https://trid.trb.org/View/2499284</link>
      <description><![CDATA[Public highway agencies encourage the use of recycled asphalt materials (RAM) in constructing pavements to the maximum extent possible with an equal performance. Low temperature cracking potential is a primary concern with high RAM mixtures, which is caused by the aging of asphalt through the oxidation. To minimize a low temperature cracking, various rejuvenators have been utilized in the past instead of bumping down a PG grade of the specified virgin asphalt for high RAM mixes. Although the current Iowa DOT’s specification allows RAP materials up to 30% with softer binder, limited construction projects have been performed, which utilized more than 20% RAP materials. The main purpose of this research is to evaluate high RAM mixtures up to 45% RAP with rejuvenators for Iowa DOT and local public agencies by performing laboratory tests and field implementation. The specific findings from this study include: • Rejuvenators consistently lowered both critical high and low temperatures of virgin binder of PG 58-28S. • Due to its high variability, FTIR could not determine the effectiveness of rejuvenators in lowering the aging of RAP binder. • 34% and 45% High RAP mixtures with rejuvenators were compacted well exceeding 93% field density. • Based on HWT test results, field mixtures with rejuvenators performed better in rutting performance than ones without. • Based on DCT test results, field mixtures with soft binder endured the highest fracture energy. • Based on SCB-IFIT test results, rejuvenators improved cracking resistance of RAP mixtures but not RAS mixtures. • Based on test results of both DCT and SCB-IFIT, there was a good correlation between test results of SCB-IFIT and DCT. • Based on a condition survey of test sections performed after one year since construction, all test sections performed very well with very little distress whereas test sections without rejuvenators developed several hairline cracks. Rejuvenators were effective in delaying an initiation of cracking. • When mixtures with rejuvenators were aged, rutting decreased in HWT test but cracking increased in SCB-IFIT test. • Both 34% and 45% RAP mixtures with rejuvenators were successfully constructed. For future studies, an approval process for rejuvenators that incorporates long-term aging of the material should be developed. Increasing the maximum RAM percentage up to 50% should be considered for some mixes with additional options for RAM use and binder formulations, which may provide greater flexibility to contractors and binder suppliers. High RAM project sites should be monitored to determine the effectiveness and limitations of design, construction and performance of high RAM mixtures and develop QA/QC aspect of using softer binders and rejuvenators. Finally, a comprehensive asphalt recycling strategy encompassing high RAM mix up to 50%, CIR and HIR should be developed in consideration of both economic and sustainability analyses.]]></description>
      <pubDate>Tue, 25 Mar 2025 16:57:57 GMT</pubDate>
      <guid>https://trid.trb.org/View/2499284</guid>
    </item>
    <item>
      <title>Cold In-Place Recycling Project Selection and Guidance for Iowa Roadways</title>
      <link>https://trid.trb.org/View/2499285</link>
      <description><![CDATA[Cold in-place recycling (CIR) involves cold milling 3 to 4 in. of a deteriorated asphalt pavement, processing and stabilizing the millings, and relaying, compacting, curing, and covering with a hot-mix asphalt (HMA) overlay or (rarely in Iowa) a bituminous surface treatment. This report documents an investigation of CIR projects in Iowa with the objective of understanding CIR pavement deterioration processes so that improvements can be made in project selection, design, construction, and maintenance. Multiple research methods were used, including a literature review, a meta-analysis of the literature, database analysis, recovery of field pavement cores and milling samples, laboratory testing, and development of conclusions and recommendations. Analysis of 44 CIR pavement projects from the Iowa Pavement Management Information System database showed that rutting was the distress that triggered performance concerns first, followed by longitudinal wheel path cracking and transverse cracking. Pavement distress indices typically dropped below trigger values 10 to 15 years after CIR rehabilitation, and thicker CIR and HMA layers were associated with better performance outcomes. Laboratory testing of field cores recovered from an Iowa CIR pavement with performance issues confirmed that the flexibility of the CIR pavement layers was greater than that of the overlaid HMA layers. Since CIR layers have a relatively high air void ratio, a possible deterioration process was postulated where heavy wheel loads cause compaction rutting in the CIR layer, which in turn causes the less flexible HMA layer to longitudinally crack in the wheel path after it is forced to conform to the rutted CIR cross section. Resulting recommendations are to specify a more flexible HMA overlay, use rut filling treatments after ruts appear, and avoid selecting CIR for roads that experience many heavy wheel loads. This report also documents a forensic case study of two low-volume roads that did not meet performance expectations and a comparison of asphalt milling gradations from CIR versus hot in-place recycling (HIR) projects. The forensic study showed that pavement thicknesses were less than planned, the pavement structure was insufficient for typical local subgrade strengths, and gradations were finer than expected. In the gradation comparison, HIR millings were confirmed to be coarser than CIR millings.]]></description>
      <pubDate>Tue, 25 Mar 2025 16:57:57 GMT</pubDate>
      <guid>https://trid.trb.org/View/2499285</guid>
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