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    <title>Transport Research International Documentation (TRID)</title>
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    <language>en-us</language>
    <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>Transport Research International Documentation (TRID)</title>
      <url>https://trid.trb.org/Images/PageHeader-wTitle.jpg</url>
      <link>https://trid.trb.org/</link>
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    <item>
      <title>Design Guidelines for Horizontal Sightline Offsets</title>
      <link>https://trid.trb.org/View/1649937</link>
      <description><![CDATA[This report provides guidance for highway agencies to address the types of sight distance restrictions that are most likely to be encountered on specific roadway types. The guidelines identify design situations that address the relative cost of removing the sight restriction and the likely implications for safety of allowing the sight distance restriction to remain. When a decision is reached not to remove a sight restriction, the guidelines include a catalog of mitigation strategies for consideration in specific design situations on specific roadway types.  Individual chapters address:  design criteria for horizontal sight obstructions (HSOs); relationship of sight distance to crash frequency and severity; benefit-cost analysis; reliability analysis model for horizontal curves with limited stopping sight distance; assessing removal or mitigation of HSOs; and design exceptions and mitigation strategies.]]></description>
      <pubDate>Thu, 12 Sep 2019 11:32:54 GMT</pubDate>
      <guid>https://trid.trb.org/View/1649937</guid>
    </item>
    <item>
      <title>ROCA - An ArcGIS toolbox for road alignment identification and horizontal curve radii computation.</title>
      <link>https://trid.trb.org/View/1630017</link>
      <description><![CDATA[The authors present the ROCA (ROad Curvature Analyst) software, in the form of an ESRI ArcGIS Toolbox, intended for vector line data processing. The software segments road network data into tangents and horizontal curves. Horizontal curve radii and azimuth of tangents are then automatically computed. Simultaneously, additional frequently used road section characteristics are calculated, such as the sinuosity of a road section (detour ratio), the number of turns along an individual road section and the average cumulative angle for a road section. The identification of curves is based on the naive Bayes classifier and users are allowed to prepare their own training data files. The authors applied ROCA software to secondary roads within the Czech road network (9,980 km). The data processing took less than ten minutes. Approximately 43% of the road network in question consists of 42,752 horizontal curves. The ROCA software outperforms other existing automatic methods by 26% with respect to the percentage of correctly identified curves. The segmented secondary roads within the Czech road network can be viewed on the roca.cdvgis.cz/czechia web-map application. The authors combined data on road geometry with road crashes database to develop the crash modification factors for horizontal curves with various radii. The authors determined that horizontal curves with radii of 50 m are approximately 3.7 times more hazardous than horizontal curves with radii accounting for 1000 m. ROCA software can be freely downloaded for noncommercial use from https://roca.cdvinfo.cz/ website.]]></description>
      <pubDate>Wed, 19 Jun 2019 11:05:16 GMT</pubDate>
      <guid>https://trid.trb.org/View/1630017</guid>
    </item>
    <item>
      <title>Safety Evaluation of Geometric Design Criteria: Horizontal Curve Radius and Side Friction Demand on Rural, Two-Lane Highways</title>
      <link>https://trid.trb.org/View/1583909</link>
      <description><![CDATA[AASHTO’s A Policy on Geometric Design of Highways and Streets, 6thEdition, provides design criteria for horizontal curve elements based on the point-mass model. The model equates the centripetal force needed to navigate a horizontal curve of a specific radius traveling at the design speed to the combination of superelevation rate and side friction needed to achieve that force. Few researchers have examined the safety impacts of horizontal curve radius, superelevation rate, and design speed through crash-based research. None of the research reviewed included the effects of design speed or superelevation rate in the crash modification factors (CMFs) or functions. This research explored these factors using a negative binomial regression modeling approach based on data collected from the SHRP 2 RID 2.0 for 889 horizontal curves on rural two-lane highways in Indiana and Pennsylvania, which resulted in roadway departure crash modification functions for horizontal curve radius and side friction demand. The crash modification function for side friction demand includes an interactive component of horizontal curve radius and speed and a direct effect of superelevation rate on roadway departure crashes. The results showed that roadway departure crashes are expected to increase for decreasing curve radius, increasing posted speed limit, and decreased superelevation rate. Furthermore, curve-related CMFs were sensitive to the curve radii used in their development. CMFs developed from curves with larger radii tended to result in larger CMFs. Sample applications are provided for computing the effects of changing the horizontal curve radius, posted speed limit, or both on proposed alternatives.]]></description>
      <pubDate>Fri, 15 Mar 2019 14:48:19 GMT</pubDate>
      <guid>https://trid.trb.org/View/1583909</guid>
    </item>
    <item>
      <title>Safety Evaluation of Horizontal Alignment Design Consistency on Rural Two-Lane Highways</title>
      <link>https://trid.trb.org/View/1581747</link>
      <description><![CDATA[Design consistency in the context of highway and street design refers to the conformance of highway geometry to driver expectancy. Existing design policies provide guidance related to horizontal alignment design consistency. While design consistency has safety implications and is intuitively linked to roadway departure crashes, the authors are only aware of a few studies that sought to link measures of design consistency to safety performance. This study explores relationships between alternative measures of horizontal alignment design consistency and the expected number of roadway departure crashes along horizontal curves on rural, two-lane, two-way roads. The authors analyzed 854 horizontal curves on rural two-lane highways in Indiana and Pennsylvania using data obtained from the SHRP 2 Roadway Information Database (RID) 2.0. Relationships between measures of design consistency and the expected number of roadway departure crashes were explored using a negative binomial regression modeling approach. The results indicate a relationship between the frequency of roadway departure crashes on a study curve and the radii of upstream and downstream curves. The ratio of the length of upstream and downstream tangents relative to a study curve radius was also statistically significant in Pennsylvania. Such findings are intuitive given the concept of design consistency and represent an advancement to existing predictive methods in the AASHTO Highway Safety Manual, which estimate the expected number of crashes on a segment as a function of the characteristics of only that segment.]]></description>
      <pubDate>Tue, 19 Feb 2019 15:10:36 GMT</pubDate>
      <guid>https://trid.trb.org/View/1581747</guid>
    </item>
    <item>
      <title>Probabilistic, safety-explicit design of horizontal curves on two-lane rural highways based on reliability analysis of naturalistic driving data</title>
      <link>https://trid.trb.org/View/1573514</link>
      <description><![CDATA[The high collision rates on horizontal curves compared to other roadway elements make them one of the most critical elements in a transportation network. In this regard, it is important to develop models to predict the safety performance of the horizontal curves. A considerable number of studies have been conducted to develop safety performance functions based on several concepts such as geometric characteristics, design consistency, reliability analysis, and comfort threshold. However, these models do not account for all horizontal curve design criteria or consider several cases such as driving in adverse weather conditions or on pavement of low available friction. This paper develops a probabilistic, safety explicit approach of horizontal curve design using reliability analysis of four design criteria: vehicle stability, driver comfort, sight distance, and vehicle rollover. Two situations were considered in the analysis: driving in clear weather (dry pavement) and raining weather (wet pavement) to develop safety performance functions for annual and five-year collision frequency. Four types of regression models, Poisson, negative binomial, zero-inflated Poisson, and zero-inflated negative binomial, were used in the analysis. The AIC, BIC, and Vuong test were used in evaluating the developed models.]]></description>
      <pubDate>Mon, 28 Jan 2019 10:13:14 GMT</pubDate>
      <guid>https://trid.trb.org/View/1573514</guid>
    </item>
    <item>
      <title>Influence of Horizontal Curvature on the Shear Resistance of Steel Plate Girders with Slender Webs</title>
      <link>https://trid.trb.org/View/1556819</link>
      <description><![CDATA[Steel plate girders have been used as bridge structural components for over two hundred years. Given technology and material advancements, steel plate girders and their elements (webs and flanges), continue to become slenderer. As a result, elastic buckling is a concern when evaluating shear capacity. This issue has been addressed for straight girders by a number of researchers, most notably via the development of the theory of tension field action (TFA). To date, horizontal curvature effects have not been included in design of steel bridges, however others have investigated horizontal curvature effects on slender, shear panel behavior and capacity (1). This paper summarizes an ongoing study investigating how horizontal curvature influences the shear buckling capacity and ultimate shear resistance in steel plate girders with slender webs. Results show that horizontal curvature can affect the shear capacity and a proposed shear buckling coefficient produces accurate results.]]></description>
      <pubDate>Fri, 30 Nov 2018 09:39:09 GMT</pubDate>
      <guid>https://trid.trb.org/View/1556819</guid>
    </item>
    <item>
      <title>Stopping sight distance adequacy assessment on freeways: the case of left horizontal curves over crest vertical curves</title>
      <link>https://trid.trb.org/View/1564425</link>
      <description><![CDATA[This paper investigates potential Stopping Sight Distance (SSD) violation on divided highways at left horizontal curves overlapped with crest vertical curves. The authors previously developed a SSD control methodology that relates the 3D configuration to the dynamics of a vehicle moving along the roadway. This methodology is applied for the assessment of critical design parameters related to both demanded and available SSD values. Initially, utilizing control geometric and driver – obstacle values adopted by AASHTO 2011 design policy, SSD inadequacy areas were revealed. Subsequently, on the basis of an explanatory modeling approach for a number of geometry parameters, evaluation of SSD sufficiency was carried out in terms of the probability of SSD inadequacy and the prediction of the object height in order to grant SSD adequacy (amended object height). These models may be useful to researchers and practitioners aiming to evaluate the interaction of the utilized design parameters in terms of SSD inadequacy.]]></description>
      <pubDate>Fri, 26 Oct 2018 10:34:26 GMT</pubDate>
      <guid>https://trid.trb.org/View/1564425</guid>
    </item>
    <item>
      <title>Comparative Analysis of Modal Responses for Reinforced Concrete (RC) Straight and Curved Bridges</title>
      <link>https://trid.trb.org/View/1421128</link>
      <description><![CDATA[On the territory of Montenegro, road straight and curved bridges with middle range spans are often frame structures with multi column bent type and a capping beam. This paper presents the response of three reinforced concrete (RC) bridges: two curved bridges (with radius R=250 m and R=150 m) and one straight bridge. Bridges under consideration are frame structures with multi column bent (two circular columns) and capping beam integrated into the deck. Skewness of the bridge bent is also considered in this paper. Three angles of skew are analyzed: 0°, 20° and 30°. Significant mode shapes are obtained through modal analysis. Comparative analysis of modal responses is carried out and conclusions about the influence of skewness and horizontal curve on modal shapes and periods of vibrations are made. Static-nonlinear analysis was performed for all nine bridge prototypes. The obtained results were compared and conclusions about influence of considered geometric parameters were made.]]></description>
      <pubDate>Wed, 19 Oct 2016 11:00:56 GMT</pubDate>
      <guid>https://trid.trb.org/View/1421128</guid>
    </item>
    <item>
      <title>'Curve' Appeal: High Friction Surface Treatments Key to Safer Pavements</title>
      <link>https://trid.trb.org/View/1416586</link>
      <description><![CDATA[Great efforts are being made by many states to improve safety on horizontal curves, an area that accounts for a large percentage of fatal crashes on highways. High friction surface treatment (HFST) is one of the effective countermeasures that transportation agencies can utilize, as explained in this article. Among the related issues explored are substrate strength, deployment factors, HFST cost effectiveness, and the future of HFST.]]></description>
      <pubDate>Wed, 27 Jul 2016 09:49:44 GMT</pubDate>
      <guid>https://trid.trb.org/View/1416586</guid>
    </item>
    <item>
      <title>Development of the ConnDOT Horizontal Curve Classification Software- Phase II</title>
      <link>https://trid.trb.org/View/1402166</link>
      <description><![CDATA[Horizontal curves are an integral part of roadway design; they provide a transition between tangents on a roadway. While many types of horizontal curves can be used in the geometric design of a roadway, simple circular curves are typically used. Other curve types that can be used include compound and spiral curves. The development of a quick, reliable, and efficient method for identification of horizontal curves and extraction of their geometric parameters from road inventory data is of immense benefit to transportation agencies and traffic safety. Efficient and reliable identification of horizontal curves and extraction of geometric parameters like radius, degree of curvature, point of curvature, and point of tangency can be used by transportation agencies to set advisory speeds, perform design and safety audits, select placement of curve warning signs, and evaluate vehicle crashes that occur at or near horizontal curve locations on the roadway. Phase II of this project attempts to create a software package that can automate the process of identifying the point of curvature and point of tangency of every curve on the state network in Connecticut. Using five designed curves and the reverse run of the same stretch of roadway a software package was developed. Each curve on the state system was identified and the roadway geometry for each curve was calculated.]]></description>
      <pubDate>Wed, 27 Apr 2016 17:54:07 GMT</pubDate>
      <guid>https://trid.trb.org/View/1402166</guid>
    </item>
    <item>
      <title>Horizontal Curvature Influence on Shear in Steel Plate Girders</title>
      <link>https://trid.trb.org/View/1393691</link>
      <description><![CDATA[Steel plate girders are typically used for bridges having unbraced length to radius of curvature (Lb/R) ratio less than 0.10 and for bridge spans between 150' (45.72 m) and 300' (91.44 m) (1,2). These girders typically have slender webs that reduce self-weight while still maintaining acceptable capacity. The use of slender webs influences shear stiffness which, subsequently, allows the web to undergo buckling prior to yielding. While it is recognized that post-buckling capacity does exist in the web and well-founded methodologies, such as tension-field action, have been developed to account for this capacity, it is understood that some residual shear strength could be sacrificed when the web buckles in shear (2). It is also recognized that horizontal web curvature of restrained plates introduces additional out-of-plane stiffness, which delays the onset of buckling, possibly a beneficial effect of curvature. However, effects of horizontal curvature on ultimate shear strength are not well understood and it can be surmised that reduction in ultimate load may accompany the enhanced buckling resistance. This paper summarizes an ongoing study examining the effect horizontal curvature has on web shear behavior. This was accomplished by computationally examining the response of representative simply supported, horizontally curved, steel plate girders to failure in three point bending. The study investigated a range of girder radii, web slenderness (D/tw), and web panel aspect ratios (do/D). Findings from the study demonstrated shear buckling capacity and ultimate shear strength are affected by curvature over a range of realistic web slenderness and panel aspect ratios.]]></description>
      <pubDate>Tue, 15 Mar 2016 10:10:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/1393691</guid>
    </item>
    <item>
      <title>New Approach for Managing Pavement Friction and Reducing Road Crashes</title>
      <link>https://trid.trb.org/View/1393670</link>
      <description><![CDATA[Evaluation of crash count data as a function of roadway characteristics allows departments of transportation (DOTs) to predict expected average crash risks to assist in identifying segments that could benefit from various treatments. Crash risk is modeled using negative binomial regression, as a function of annual average daily traffic (AADT) and other variables. For this paper, a crash study was carried out for the Interstate, primary, and secondary routes in the Salem District of Virginia. The data used in the study included the following information obtained from Virginia DOT records: 2010 to 2012 crash data, 2010 to 2012 AADT, and horizontal radius of curvature. In addition, tire–pavement friction, or skid resistance, was measured with a continuous friction measurement, fixed-slip device called a GripTester. Negative binomial regression was used to relate the crash data to the AADT, skid resistance, and horizontal radius of curvature. To determine which of the variables to include in the final models, researchers performed the Akaike information criterion test. By mathematically combining the information acquired from the negative binomial regression models and the information contained in the crash counts, researchers empirically estimated the parameters of each network’s true average crash risks with the empirical Bayes approach. The new estimated average crash risks were then used to rank segments according to their empirically estimated crash risk and to prioritize segments according to their expected crash reduction if a friction treatment were applied.]]></description>
      <pubDate>Sat, 05 Mar 2016 11:29:40 GMT</pubDate>
      <guid>https://trid.trb.org/View/1393670</guid>
    </item>
    <item>
      <title>Effects of Cross-Slope Break on Roadway Departure Recovery for Trucks on Horizontal Curves</title>
      <link>https://trid.trb.org/View/1392898</link>
      <description><![CDATA[A 2009 crash involving a tanker truck that departed the roadway on a freeway connection ramp led the National Transportation Safety Board to suggest a review of current AASHTO policy for pavement–shoulder cross-slope breaks on horizontal curves to determine whether updates to the design criteria were needed. As part of NCHRP Project 03-105, the research team reviewed and summarized existing policies and conducted a pair of studies focusing on large trucks on horizontal curves. Researchers conducted a vehicle dynamics simulation study and a crash-based study; both were designed to identify patterns and trends in roadway departure crashes involving large trucks and to develop recommendations for corresponding revisions to AASHTO policy for designing cross-slope breaks on horizontal curves. In the vehicle dynamics simulation study, researchers developed and analyzed results from roadway departure models for a tractor single-van trailer truck, a tractor tanker trailer truck, and a tractor double-van trailer truck for various combinations of roadway departure path, approach speed, superelevation, and cross-slope break. This paper summarizes existing policy, describes the study method, and presents findings from the vehicle dynamics simulation study. Results indicate that no changes need to be recommended for AASHTO’s policy on cross-slope break.]]></description>
      <pubDate>Fri, 15 Jan 2016 15:05:22 GMT</pubDate>
      <guid>https://trid.trb.org/View/1392898</guid>
    </item>
    <item>
      <title>Automated Horizontal Curve Classification and Parameter Calculation Methods Using Vehicle-Collected Road Inventory Data</title>
      <link>https://trid.trb.org/View/1338785</link>
      <description><![CDATA[Horizontal curves have been associated with vehicle crashes and accidents on the roadways. The identification and extraction of road horizontal curve parameters therefore has potential applications in the identification of high risk locations and evaluation of the safety performance of roads. A simple methodology to extract horizontal curve parameters and classify both horizontal curves and vertical grades using vehicle collected road inventory data and Highway Performance Monitoring System (HPMS) classification schemes is presented. The method developed, referred to as the per point classification method, extracts horizontal curve parameters using vehicle heading data and equations for a simple circular horizontal curve. Smoothing techniques are applied to the heading data to remove anomalies and extremities before horizontal curve parameter extraction is executed. The method is validated using curves from the design drawings of two routes in Connecticut (CT). In addition to the extraction of horizontal curve parameters and classification of horizontal curves and vertical grades, the length of each horizontal curve and vertical grade type within HPMS designated sections of the different routes within inventory data are extracted. The classification and length extraction of horizontal curves and vertical grades types are automated and deployed in two standalone MATLAB executable applications for fast and efficient processing of the data.]]></description>
      <pubDate>Wed, 18 Feb 2015 12:00:39 GMT</pubDate>
      <guid>https://trid.trb.org/View/1338785</guid>
    </item>
    <item>
      <title>Development of the ConnDOT Horizontal Curve Classification Software</title>
      <link>https://trid.trb.org/View/1320982</link>
      <description><![CDATA[The Highway Performance Monitoring System (HPMS) is a national, highway information system that requires states to collect and submit data on the extent, condition, performance, use, and operating characteristics of the nation's highways. HPMS requirements include limited data on all public roads, with more detailed data for sample sections of the arterial and collector functional classes. One of the field inventory reviews that many states have a difficult time reporting efficiently is the required horizontal curve classification for each HPMS section. Connecticut has more than 2000 HPMS sites making manual updates to these sections very difficult and time consuming. Automated methods to create a batch reporting process could save significant time and effort while increasing the accuracy with which data are reported to the Federal Highway Administration (FHWA). Connecticut is fortunate in that the department of transportation performs an annual photolog survey of all state roads and conducts supplemental data collection runs for HPMS sections. This report details the creation of an automated curve classification software kit to generate grade and horizontal curve classification files for HPMS reporting.]]></description>
      <pubDate>Wed, 27 Aug 2014 11:23:44 GMT</pubDate>
      <guid>https://trid.trb.org/View/1320982</guid>
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