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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>
    <image>
      <title>Research in Progress (RIP)</title>
      <url>https://rip.trb.org/Images/PageHeader-wTitle-RIP.jpg</url>
      <link>https://rip.trb.org/</link>
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    <item>
      <title>Developing Guidance on the Safety Performance of Edge Line Pavement Markers and Guardrail Delineations on Rural Oregon Roads</title>
      <link>https://rip.trb.org/View/2724855</link>
      <description><![CDATA[Despite Oregon's efforts to reduce fatalities and serious injuries, crashes along curves (statewide) continue to be high-risk locations, particularly those involving roadway departures.  Contributing factors such as speed, visibility, pavement quality, limited delineation, and adverse weather conditions exacerbate these risks.  While Oregon incorporates edge line pavement markers and guardrail delineations, there is limited research on their safety performance on Oregon specific rural roads. It will also investigate whether combining edge line pavement markers with guardrail and barrier delineations as part of a systemic safety countermeasure strategy provides greater safety benefits than applying treatments individually.

This research will produce a guidance document outlining recommendations for the use of edge line pavement markers and guardrail delineations on rural curves.  The document will provide: (1) criteria for identifying high-risk curves where these treatments will be most effective, considering factors such as crash history, speed, curve geometry, and environmental conditions; (2) guidance on combining edge line pavement markers with guardrail and barrier delineations as a systemic safety countermeasure strategy to achieve greater safety benefits; (3) scalable solutions tailored to rural curves that address Oregon’s unique roadway environments and crash patterns; and (4) performance evaluation framework for ongoing assessment and monitoring of these countermeasures.]]></description>
      <pubDate>Wed, 08 Jul 2026 15:06:03 GMT</pubDate>
      <guid>https://rip.trb.org/View/2724855</guid>
    </item>
    <item>
      <title>Scoping Study: Vertical Visibility Constraints -- Vertical Curvature Traffic Control Devices</title>
      <link>https://rip.trb.org/View/2709249</link>
      <description><![CDATA[Horizontal and vertical curves can obscure key roadway features or activity that may lie ahead of unaware drivers. Roadway curvature is a significant factor in roadway departure crashes, injuries, and fatalities. As land use has developed and activities on roads have changed, the potential for conflicts has grown. It is impractical and beyond the resources of roadway authorities to improve all roadway alignments to attain optimal sight distance. This is a growing concern as active transportation increases in many rural areas, especially those experiencing increased tourism. Horizontal curvature on roadways where drivers’ views are obstructed has been thoroughly researched, leading to well-accepted strategies for traffic control devices in the Manual on Uniform Traffic Control Devices (MUTCD). However, similar research has yet to be conducted for vertical curves.

OBJECTIVE; The objective of this research is to develop a scoping study to clearly define and refine the research needs, objectives, and expected products necessary to address vertical visibility constraints, including exploring the relevance of crash data to vertical curves and developing a research work program to explore solutions. The intent of potential larger, follow-on, NCHRP study is to obtain data from vertical-curvature-related crashes to assess the details of occurrence, frequency, and severity, and to better understand road user needs, rather than relying on approaches used in prior studies.]]></description>
      <pubDate>Tue, 02 Jun 2026 13:49:43 GMT</pubDate>
      <guid>https://rip.trb.org/View/2709249</guid>
    </item>
    <item>
      <title>Impact of Pavement and Weather Conditions on Traffic Speed at Sharp Horizontal Curves  </title>
      <link>https://rip.trb.org/View/2646943</link>
      <description><![CDATA[Lane departure crashes on sharp horizontal curves are a major safety concern on both highways and freeways, accounting for a disproportionately high number of fatal and severe injury crashes. Research has shown that these crashes are often linked to speeds relative to curve geometry. While geometric design factors like curve radius and superelevation have been well studied, less attention has been given to how pavement and weather conditions influence traffic speed on these elements. Particularly, current safety models do not fully account for the effects of pavement surface conditions, such as friction, roughness, and texture, or adverse weather elements like precipitation, temperature drops, and reduced visibility. While the impact of factors like road curvature effects on traffic speed have been studied, current models often fail to integrate the complex interaction of pavement conditions and weather data in predicting traffic speeds. This results in inaccurate speed predictions, which can compromise safety and infrastructure planning. Without comprehensive, data-driven models, interventions such as speed limits, signage, or road maintenance are often poorly targeted, leading to higher risks of crashes, congestion, and inefficient resource allocation. The motivation for this project is to develop a predictive model that integrates pavement conditions, weather effects, and road geometry to estimate traffic speed at horizontal curves. This will provide safer roads by enabling better traffic management, targeted infrastructure improvements, and more efficient interventions. ]]></description>
      <pubDate>Mon, 05 Jan 2026 23:07:35 GMT</pubDate>
      <guid>https://rip.trb.org/View/2646943</guid>
    </item>
    <item>
      <title>Development of a Network-Level Data-Driven High Friction Surface Treatment Location Selection Approach Leveraging Remote Sensing Technologies</title>
      <link>https://rip.trb.org/View/2643023</link>
      <description><![CDATA[High Friction Surface Treatment (HFST) is an effective countermeasure for reducing crashes at horizontal curves, yet current site selection practices rely heavily on historical crash data and manual field inspections. These approaches limit agencies’ ability to proactively identify high-risk locations and efficiently allocate limited safety resources. This project addresses these limitations by developing a scalable, data-driven framework for HFST site prioritization at the network level.

The research will create an automated data-processing pipeline that extracts roadway geometry and surface characteristics from mobile LiDAR and video log imagery, including curve radius, superelevation, signage, and surface condition. These features will be integrated with pavement condition and crash data to identify high-risk and constructible HFST locations. The approach will be validated through a case study using Massachusetts Department of Transportation (MassDOT) roadway and crash data. Results will provide transportation agencies with a transferable methodology for proactive HFST deployment, improving safety outcomes and supporting more efficient infrastructure management.]]></description>
      <pubDate>Thu, 18 Dec 2025 14:36:51 GMT</pubDate>
      <guid>https://rip.trb.org/View/2643023</guid>
    </item>
    <item>
      <title>High Friction Surface Treatment Decision-Making Criteria </title>
      <link>https://rip.trb.org/View/2640691</link>
      <description><![CDATA[Between the years of 2019 and 2023, there were 203,662 run-off-road (ROR) crashes in Missouri resulting in 1,983 fatalities and 9,428 severe injuries. One safety countermeasure used by state departments of transportation (DOT) to address ROR crashes is called a high friction surface treatment (HFST). The goal of this research project is to provide the Missouri Department of Transportation (MoDOT) with criteria to help proactively identify locations for potential friction treatment applications. An ideal situation would be to calculate the minimum friction at a given curve location and have a list of friction treatment options (e.g., HFST, superelevation adjustments, curve realignment, and others). These criteria would be incorporated into MoDOT’s Engineering Policy Guide (EPG).]]></description>
      <pubDate>Tue, 16 Dec 2025 09:20:39 GMT</pubDate>
      <guid>https://rip.trb.org/View/2640691</guid>
    </item>
    <item>
      <title>Evaluating Method 2 Horizontal Curvature in Freeway Work Zones: Safety, Suitability, and Alternatives</title>
      <link>https://rip.trb.org/View/2608464</link>
      <description><![CDATA[In freeway design, Method 5 is the standard approach for determining horizontal curvature on high-speed highways, while Method 2 is intended for low-speed urban facilities where higher side friction values are acceptable. However, in Utah, Method 2 has been implemented in high-speed freeway work zones through Alternative Technical Concepts
(ATCs), most notably on the I-15 Technology Corridor project. Post-construction crash records revealed truck overturning incidents and other safety concerns, raising questions about the suitability of Method 2 in high-speed environments.

While Utah Department of Transportation (UDOT) has already developed a five-year statewide database of work zones containing crash data (AASHTOWare Safety) and project details (Masterworks), this database does not distinguish between projects that used Method 2 horizontal curvature versus standard lane-shift tapers (Method 5). Without this distinction, UDOT lacks the ability to directly assess whether Method 2 increases crash severity, particularly for heavy vehicles, in comparison to established design practices. This gap in knowledge is critical given the safety implications for drivers and workers in high-speed freeway work zones, as well as the need to guide ATC approvals on future Design-Build projects.

This research is needed to provide UDOT with a data-driven evaluation of Method 2’s risks, safety impacts, and design suitability in freeway work zones. Findings will clarify whether Method 2 should remain an acceptable option and under what conditions it might be safely applied.]]></description>
      <pubDate>Mon, 13 Oct 2025 19:12:31 GMT</pubDate>
      <guid>https://rip.trb.org/View/2608464</guid>
    </item>
    <item>
      <title>Evaluating the Effectiveness of Dynamic Speed Feedback Sign (DSFS) at Safety Critical Locations in Connecticut </title>
      <link>https://rip.trb.org/View/2566902</link>
      <description><![CDATA[This research study will use the field data collected at horizontal curves and speed transition zones to evaluate the effectiveness of dynamic speed feedback sign (DSFS) in improving speed compliance at these locations. The research team will extensively collect speed data at numerous horizontal curves and speed transition zones to obtain a meaningful sample size; and estimate the ideal range of longitudinal position of DSFS that produces maximum impact on speed.]]></description>
      <pubDate>Wed, 18 Jun 2025 13:29:07 GMT</pubDate>
      <guid>https://rip.trb.org/View/2566902</guid>
    </item>
    <item>
      <title>Performance-Based Superelevation Design Criteria



</title>
      <link>https://rip.trb.org/View/2381751</link>
      <description><![CDATA[Advances in the automobile industry, along with the introduction of automated and electric vehicles, have changed vehicle dynamics when navigating curves, particularly in superelevation transitions and fully superelevated sections. Side friction factors based on older vehicle models may no longer align with modern vehicles, vehicle dynamics technologies such as electronic stability control, tire technologies, and pavement surface courses.

Given the advancements in the vehicle fleet, alternative design models should be evaluated for their ability to account for factors such as grade and acceleration/deceleration. Research is needed to update superelevation design criteria based on the impact of these advancements to ensure that horizontal curve designs meet or exceed the safety and performance standards required by modern vehicles and roads.

OBJECTIVE: The objective of this research is to develop performance-based superelevation design criteria. The criteria shall be based on the interaction between vehicles and horizontal curves, performance measures related to safety and user comfort, and acceptable design and construction tolerances.]]></description>
      <pubDate>Thu, 23 May 2024 10:24:25 GMT</pubDate>
      <guid>https://rip.trb.org/View/2381751</guid>
    </item>
    <item>
      <title>SPR 771 Safety Analysis of Highway Curves Where Crashes Occur in South Carolina</title>
      <link>https://rip.trb.org/View/2334168</link>
      <description><![CDATA[A recent study conducted by this research team of over 900 2019 South Carolina fatal crashes 
showed that nearly 20 percent occurred on highway horizontal curves. The study further 
identified that 25% of the curves where these crashes occurred may have had design speeds less 
than the posted speed limit and 47% of the curves have a design speed less than 5 mph above the 
speed limit. Prior research on operating speeds indicates that drivers tend to drive at least 7-10 
mph above the posted speed limit. With design speeds below or right at the posted speed limit, 
excess speed of any level can become problematic. This research focuses on a detailed analysis 
of curves where vehicle crashes occur in South Carolina compared to similar radii highway 
curves that have a significantly lower crash incidence. The existing inventory of circular curves 
along with crash data will need to be analyzed to identify trends and the effectiveness of 
countermeasures. There are some known issues with the Rieker highway curve inventory. 
Some of these issues will be corrected as part of this research. These issues include locations 
identified as curves that are actually intersections and correctness of attributes essential for safety 
analysis. The Manual on Uniform Traffic Control Devices (MUTCD) compliance issues related to horizontal alignment warning information is a 
concern of South Carolina Department of Transportation (SCDOT). This research will help to address that concern.]]></description>
      <pubDate>Thu, 01 Feb 2024 09:47:34 GMT</pubDate>
      <guid>https://rip.trb.org/View/2334168</guid>
    </item>
    <item>
      <title>Evaluation of Post Mounted Delineators and Curve Warning Message Markings</title>
      <link>https://rip.trb.org/View/2219413</link>
      <description><![CDATA[The purpose of this study is to evaluate post-mounted delineators and curve warning message markings by deploying them on a sample of VDOT roads based on a statistically robust sampling plan. This will be accomplished in three phases. This project will conduct the first phase of this study.  Tasks in the first phase include conducting a literature review and outreach to determine best design and maintenance practices, identifying the specifications for modification, and designing a sampling plan. A second phase will deploy and monitor the two treatments in the field following the plan developed in the Phase 1 study. A phase 3 study would conduct the before and after crash analysis, crash modification factor (CMF) development and benefit-cost analysis. This study fits well into current VDOT safety programs, policies, and initiatives for reducing roadway departure crashes (RDCs).  Positive research results would provide additional countermeasures statewide for RDCs that will benefit the ongoing systemic safety program.  VDOT will benefit from the development of CMFs specific to Virginia by determining the expected return on investment in phase 3. This Phase 1 study is critical in that it provides the foundation for development of credible CMFs.]]></description>
      <pubDate>Wed, 26 Jul 2023 08:38:49 GMT</pubDate>
      <guid>https://rip.trb.org/View/2219413</guid>
    </item>
    <item>
      <title>An Enhanced Network-level Curve Safety Assessment and Monitoring Using Low-cost Mobile Devices – Refinement and Field Evaluation



</title>
      <link>https://rip.trb.org/View/2140092</link>
      <description><![CDATA[The objective of this project was to provide a viable alternative to traditional assessment methods by leveraging widely available and affordable mobile technology. This project introduces a smartphone-based curve advisory speed assessment framework that leverages the built-in GPS and Inertial Measurement Unit (IMU) sensors in low-cost mobile devices. By shifting computational tasks (e.g., superelevation calculation and advisory speed determination) to the smartphone (“edge computing”), the framework delivers immediate advisory speed results upon exiting each curve. This capability will enable the identification of inconsistent advisory speed results during field assessments, allowing engineers to investigate and verify these results immediately. By addressing inconsistencies in the field, this method can eliminate return trips caused by data quality issues, thereby improving efficiency and reducing operational costs. Additionally, cloud-based data synchronization ensures that all collected information, including newly computed advisory speeds and detected discrepancies, is stored and organized for subsequent analysis.]]></description>
      <pubDate>Mon, 20 Mar 2023 17:23:16 GMT</pubDate>
      <guid>https://rip.trb.org/View/2140092</guid>
    </item>
    <item>
      <title>Improve the Technical Capacity of Transportation Safety Professionals at all Levels of Government to Advance Safety Programs</title>
      <link>https://rip.trb.org/View/2093188</link>
      <description><![CDATA[This study presents Naturalistic Driving Data Analysis for Curves and relies on the 2nd Strategic Highway Research Program Roadway Information Database to identify geometric factors in curve-related crashes. Support for Roadway Departure, Intersections, and Pedestrian/Bicyclist Safety Focus States and Cities. The study will provide technical assistance to designated states and cities based on fatalities (e.g., develop action plans) to address Focus areas. Partners include State and local transportation agencies. The study will providing technical assistance related to bikeway selection to improve safety.  It will also develop a resource to outline principles and benefits of offset right-turn lane for application at high-speed unsignalized intersections.]]></description>
      <pubDate>Tue, 03 Jan 2023 13:53:44 GMT</pubDate>
      <guid>https://rip.trb.org/View/2093188</guid>
    </item>
    <item>
      <title>Advancing Safety Prediction Methodologies for Horizontal Curves</title>
      <link>https://rip.trb.org/View/1953246</link>
      <description><![CDATA[Statistics from the Fatality Analysis Reporting System (FARS) indicate that more than 25 percent of fatal crashes occur at horizontal curves, with most of these crashes being roadway departures. Although researchers and practitioners agree that curvature plays a role in crash frequency and severity, safety performance functions (SPFs) and severity distribution functions for horizontal curves have not been thoroughly investigated or widely implemented. 

The American Association of State Highway and Transportation Officials (AASHTO) Highway Safety Manual (HSM) provides SPFs of various facility types for segments and intersections, but not for curve segments. Rather, curves are evaluated by applying an adjustment factor (AF) to estimate the predicted crash frequency of a curve segment. Unfortunately, not all the SPF models within the HSM have AFs for horizontal curves. Recent studies have been implemented to develop AFs for curve segments of certain facility types to begin filling this gap. However, applying a horizontal curve AF to an existing segment SPF assumes that the underlying prediction model of a tangent segment only needs to be adjusted to appropriately estimate a horizontal curve’s influence on the segment’s safety performance. This method may not be the best way to assess the safety performance of horizontal curves. A more thorough investigation may reveal that common geometric attributes used to estimate the safety performance of tangent segments have a different degree of influence on the safety performance of horizontal curves. Taking this possibility further, the attributes most important for predicting the safety performance of a horizontal curve may differ due to context (rural versus urban), facility type, or other factors such as geometric and operational characteristics, and roadside elements. Therefore, additional research is needed to better understand the attributes that most influence the safety performance of horizontal curves.

OBJECTIVE: The objective of this research is to develop a guide and a tool to quantify the safety performance of horizontal curves using geometric and operational characteristics for applications across a range of highway activities including planning, design, operations, and safety management]]></description>
      <pubDate>Tue, 17 May 2022 11:30:13 GMT</pubDate>
      <guid>https://rip.trb.org/View/1953246</guid>
    </item>
    <item>
      <title>Research for AASHTO Standing Committee on Highways. Task 404. Reevaluation of the Side Friction Values used to Determine Horizontal Curve Radii Using Crash Data</title>
      <link>https://rip.trb.org/View/1877227</link>
      <description><![CDATA[The AASHTO Special Committee on Wireless Communications Technology recently reorganized to better address the challenges facing members in wireless communications and spectrum management.

The work of the committee is expanding to address the need for integrated communications systems and to facilitate education on emerging issues associated with Connected Vehicle (CV), Autonomous Vehicle (AV), spectrum management, and cybersecurity for ITS equipment. There is a strong need to formalize an ongoing program to address current communications issues and support emerging needs.

The SCOWCT committee is organized into four Technical Working Groups (TWGs): Legacy Programs; Spectrum Management; Cybersecurity; and Future and Emerging Technology. The activities and expertise of these TWGs will be leveraged to support the critical research and development of a technical framework as proposed in this project.

The project will conduct research and engagement efforts to create a technical framework for addressing ongoing transportation telecommunications issues and emerging needs through a new program facilitated by AASHTO National Operations Center of Excellence (NOCE).]]></description>
      <pubDate>Tue, 07 Sep 2021 14:04:05 GMT</pubDate>
      <guid>https://rip.trb.org/View/1877227</guid>
    </item>
    <item>
      <title>Development of a Crashworthy Tangent End Treatment for Low-Speed and Curbed Roadways</title>
      <link>https://rip.trb.org/View/1854184</link>
      <description><![CDATA[Where roadside safety barriers are desired in low-speed environments, low-profile barriers designed to address crash risks at lower speed conditions (MASH TL-2) are often favored because they are more compatible with the community context. Yet the space available for crashworthy end treatments for these barriers can be highly constrained in many urban and suburban locations because of closely spaced intersections and driveways, limited right-of-way, and the presence of street trees and other features. In addition, the presence of vertical curbs and adjacent sidewalks or multiuse paths restrict the use of a flared end treatment. Rural locations can have similar constraints and conditions, even without the presence of a curb. 
The objective of the research is to develop a nonproprietary, crashworthy tangent end treatment with the following characteristics: appropriate for urban and suburban environments; of minimal required length, width, and height; can be transitioned to commonly used rigid barriers  (e.g., TL-2 low profile or TL-3 concrete barriers); and
can be placed on top of a 6” curb or placed where there is no curb in advance of the barrier.]]></description>
      <pubDate>Tue, 25 May 2021 22:20:39 GMT</pubDate>
      <guid>https://rip.trb.org/View/1854184</guid>
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