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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>
    <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>Transport Research International Documentation (TRID)</title>
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    <item>
      <title>Study of the necessity of a speed monitoring display at the returning chicane on a freeway bypass</title>
      <link>https://trid.trb.org/View/2400550</link>
      <description><![CDATA[Roadwork zones represent a hazardous place within the highway system, with higher crash rates and injury severity, often due to excessive speed and noncompliance with speed limits. On freeways, a common layout is to close a full roadway and to divert traffic onto the opposite roadway, with one lane closed to accommodate the redirected traffic, by driving through the median strip. In this scenario, the second chicane can be a hazardous point if it is not correctly signaled. This paper examines the need to install a speed monitoring display (SMD) before the returning chicane on a bypass. A two-phase study was conducted on a Spanish freeway where a roadway was temporarily closed. Two measurement points were established on the bypass, one in the middle and one at the end, prior to the return chicane through the median strip. During Phase 1, the portable SMD was installed and during Phase 2, it was removed. The average and the 85th percentile of the speed distribution at each point during both phases were compared. Additionally, mean difference tests were conducted and a speed prediction model was developed. With the SMD, drivers reduced their speed from the midpoint to the returning chicane, within the range of 7-10 km/h. Conversely, upon removal of the SMD, motorists increased their speed while driving through the bypass, resulting in excessive speed at the most hazardous point, the chicane leading back to the original roadway. The difference in mean speed between the two phases was 18 km/h at the returning chicane. In addition to the traffic calming measures implemented prior to entering roadwork zones on freeways, which are conveniently established in the standards; it is necessary to evaluate potentially dangerous areas of the layout and implement additional measures where required. Specifically, in the case of final chicanes of bypasses with reduced radii, it is recommended that a speed monitoring display be installed as a mandatory element in order to inform drivers of this challenging segment. Highway administrations around the world should maintain a SMD at the returning chicane of a bypass while roadworks last.]]></description>
      <pubDate>Mon, 29 Jul 2024 16:27:06 GMT</pubDate>
      <guid>https://trid.trb.org/View/2400550</guid>
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    <item>
      <title>Assessing Safety Performance of Atypical Service Interchanges

</title>
      <link>https://trid.trb.org/View/2219016</link>
      <description><![CDATA[Many service interchanges include custom designs that do not fit into the traditional interchange definitions contained within the American Association of State Highway and Transportation Officials (AASHTO) Green Book, which makes it challenging to forecast and compare the relative predicted crash frequency of various atypical service interchanges. While the Highway Safety Manual (HSM) provides crash prediction for interchange elements such as basic ramps and ramp termini configurations, it does not offer a comprehensive crash prediction methodology applicable to such atypical service interchanges.

Atypical service interchanges lack a one-size-fits-all safety assessment method due to their uniqueness and complexities. To address this, engineers envision a "building-block" approach to deconstruct these interchanges into fundamental elements, e.g., ramp geometries, configurations, termini, weave segments, merge and diverge areas, access points and connections to managed lanes, active transportation, and transit facilities. This could involve assessing safety performance functions (SPFs) as well as crash modification factors (CMFs) for each element, and then aggregating these assessments to form a comprehensive analysis. However, such a generalized method is not currently available for engineers to analyze the safety performance of atypical service interchanges. 

Research is needed to apply conflict or exposure-based methods specifically tailored to these atypical service interchanges, analyzing each fundamental element, and then integrating the results from individual safety performance analyses into a comprehensive final result.

The objective of the project is to develop a method to partition interchanges into fundamental elements; analyze, quantify, and assess the safety performance of each element; and develop customized SPF models that will integrate the results from individual safety performance analyses into a comprehensive final result for atypical service interchange designs. 
]]></description>
      <pubDate>Tue, 25 Jul 2023 08:09:40 GMT</pubDate>
      <guid>https://trid.trb.org/View/2219016</guid>
    </item>
    <item>
      <title>Traffic safety analysis at interchange exits using the surrogate measure of aggressive driving behavior and speed variation</title>
      <link>https://trid.trb.org/View/2162266</link>
      <description><![CDATA[Because of heavy traffic on urban expressways, the exits of expressway interchanges have become accident-prone sites. This study explores the impacts of various traffic control devices and road conditions on road safety at interchange exits based on driving behavior data from navigation software. The traffic order index (TOI) based on driving behavior and speed variation is used to evaluate road safety. The general safety characteristics and partitioned safety characteristics of interchange exit sections for different traffic control devices and under different road conditions were described, and a structural equation model (SEM) was constructed to observe the influences of the traffic control devices, road conditions, congestion degree, and time on road safety. The results show that traffic control devices (the number of warning signs, number of advance exit signs and complexity of diagrammatic guide signs) and road conditions (the number of lanes and merging conflicts within 500 m) have significant influences on the road safety of interchange exits. Road conditions have the greatest impact on the safety of interchange exits, followed by the congestion index, traffic control devices, and time. The results could help traffic management departments reconstruct or rehabilitate traffic control devices and enable reasonable road planning at interchange exits. The safety evaluation method for traffic control devices and road conditions based on driving behavior data collected from navigation software could be further used on other roads.]]></description>
      <pubDate>Thu, 22 Jun 2023 10:10:12 GMT</pubDate>
      <guid>https://trid.trb.org/View/2162266</guid>
    </item>
    <item>
      <title>Safety Comparison of Interchange Configurations</title>
      <link>https://trid.trb.org/View/2114944</link>
      <description><![CDATA[Interchange Access Requests (IARs) document potential safety performance impacts to justify new or modified interchanges. Typically, IARs are written early in the project planning and design process, with information generally consistent with conceptual design. The details required for using the Highway Safety Manual (HSM) predictive methods for freeways, ramps, and ramp terminals are often unknown at that stage (American Association of State Highway and Transportation Officials (AASHTO) 2010). Without these details, accurately predicting crash frequency and severity for interchange components is difficult. Furthermore, aggregating site-by-site predictions may not fully capture the safety performance impacts when the project location is considered. To further explore and address the safety-related components of an IAR application, the Federal Highway Administration (FHWA) developed planning-level models and tools to predict crash frequency and severity for an existing or proposed interchange. Model inputs were limited to the following: (1) the details known at the planning and conceptual design stage, and (2) the variables expected to affect crash frequency and severity. The planning-level models allow analysts to compare the potential safety performance effects of freeway access and interchange design decisions at the planning level.]]></description>
      <pubDate>Mon, 13 Feb 2023 09:30:38 GMT</pubDate>
      <guid>https://trid.trb.org/View/2114944</guid>
    </item>
    <item>
      <title>Length of Collecting and Distributing Lane of Alfalfa Leaf Interchange Study</title>
      <link>https://trid.trb.org/View/2019082</link>
      <description><![CDATA[There is interweaving activity that takes place on the rung ramps of alfalfa leaf interchanges. The existence of these weaving sections will greatly affect the traffic capacity of the interchange. Therefore, it is necessary to set up collecting and distributing roads to increase traffic capacity and improve driving efficiency. In order to study the length of collecting and distributing lanes, this paper analyzes the factors such as marking, recognition sight distance, and the interleaving length, determining the applicable range of the length of the collector road. Finally, using VISSIM software and taking vehicle delay as the evaluation index, the authors verify the rationality of the conclusion by comparing vehicle delay under different simulation lengths.]]></description>
      <pubDate>Fri, 16 Dec 2022 09:41:10 GMT</pubDate>
      <guid>https://trid.trb.org/View/2019082</guid>
    </item>
    <item>
      <title>Applicability of Enhanced Interchange Safety Analysis Tool (ISATe) for Local Applications: A Florida Case Study</title>
      <link>https://trid.trb.org/View/1667717</link>
      <description><![CDATA[The Enhanced Interchange Safety Analysis Tool (ISATe) automates the safety evaluation procedures of freeway facilities that are discussed in the Highway Safety Manual. ISATe provides simple worksheets for data entry and facilitates the calculation of expected and/or predicted average crash frequencies for different components of a freeway facility. The ISATe models are designed to evaluate the safety performance of an existing freeway facility, or proposed design alternatives for a new interchange construction and prior to reconstruction of an existing interchange. However, these models are based on national data that may not accurately represent the local conditions. This paper describes a study to evaluate the applicability of ISATe for safety performance evaluation of interchanges in the State of Florida, United States. A before-and-after safety analysis was conducted using ISATe for five interchanges in Florida. The sites were selected based on two criteria: (i) whether crash data were available, and (ii) whether the site characteristics conform to the ISATe analysis criteria. The required roadway characteristics data were collected from different sources, including roadway characteristics inventory, aerial images, and Geographic Information Systems (GIS) maps. Based on the collected roadway and traffic features data, the observed, predicted, and expected crash frequencies by severity (i.e., total, fatal and injury (FI), and property damage only (PDO)) for both before and after periods were calculated and compared for each study interchange. The study results show that the variations between the observed and predicted FI crashes were lower compared to the variations between the observed and predicted PDO crashes. In particular, the ISATe models were found to overpredict the PDO crashes on the study interchanges. Crashes on crossroad ramp terminals were found to be highly overpredicted compared to crashes on freeways and ramps. The paper concludes by providing specific recommendations related to ISATe application in Florida.]]></description>
      <pubDate>Fri, 20 Dec 2019 16:22:33 GMT</pubDate>
      <guid>https://trid.trb.org/View/1667717</guid>
    </item>
    <item>
      <title>Application of Unmanned Aerial Vehicles to Inspect and Inventory Interchange Assets to Mitigate Wrong-Way Entries</title>
      <link>https://trid.trb.org/View/1659126</link>
      <description><![CDATA[Several previous studies have demonstrated that exit-ramp terminals are common locations for drivers to enter a physically separated highway in the wrong direction.3 Furthermore, past studies identified several common issues associated with the WWD crash-prone intersections. Issues with signing and pavement markings, including defective or missing devices, poor location or placement, and insufficient conspicuity, were commonly cited. Some geometric features also correlated to WWD crashes, such as interchange or intersection layout, the presence of raised median or channelizing islands, turning radii, and large median openings The purpose of this study, which is the first of its kind, is to evaluate the feasibility of utilizing UAVs in collecting high-quality data on exit-ramp terminals pertaining to WWD. It also discusses challenges and shortcomings, and develops solutions to address those challenges. Field data were collected at two typical freeway interchanges (i.e., partial cloverleaf interchange and modified diamond interchange) in the state of New Jersey, USA. The findings of this study could carry significant implications for state and local agencies across the nation to collect the necessary highway inventory data that can assist field inspection of WWD crash sites, with the aim of reducing the frequency and severity of WWD crashes.]]></description>
      <pubDate>Tue, 29 Oct 2019 09:32:18 GMT</pubDate>
      <guid>https://trid.trb.org/View/1659126</guid>
    </item>
    <item>
      <title>Recreational Design Guidelines to Accommodate Pedestrians and Bicyclists at Interchanges</title>
      <link>https://trid.trb.org/View/1312802</link>
      <description><![CDATA[Traditional interchange design usually does not provide adequate and safe accommodations for pedestrians and bicyclists. As a result, interchanges currently constitute significant barriers to increasing the walk and bike mode shares in transportation networks. In response to these challenges, the Pedestrian and Bicycle Council (PBC) initiated a series of interactive workshops over three years to discuss interchange design issues and opportunities with regard to pedestrian and bicyclist safety and accommodation. The PBC and the Traffic Engineering Council co-sponsored these workshops, which focused on traditional on-ramps and off-ramps, and single-point urban interchanges as representative of recent innovations in interchange design that present particular challenges for pedestrians and bicyclists. This report compiles design guidelines for improving safety and accessibility for pedestrians and bicyclists at interchanges. A number of design case studies and their recommended treatments are then developed in compliance with the design guidelines.]]></description>
      <pubDate>Mon, 30 Jun 2014 09:41:46 GMT</pubDate>
      <guid>https://trid.trb.org/View/1312802</guid>
    </item>
    <item>
      <title>Introducing Potential Benefits of and Understanding Vehicular Flows at Highway Interchange Transit Oriented Developments (HITODs)</title>
      <link>https://trid.trb.org/View/1091531</link>
      <description><![CDATA[This paper introduces the concept of a Highway Interchange Transit Oriented Development (HITODs). HITODs can redefine the interface between regional transport and suburban communities both by introducing mode choice at interchanges between highways and local roads, and by developing land left underutilized by current standard interchange designs.  By introducing new possibilities at interchanges, HITODs can help to solve problems created by existing interchange designs, including sprawl and automobile dependency. HITODs also afford new opportunities for sustainable development and value capture.  A HITOD has two primary characteristics. First, it has egress and access ramps that are optimized for express bus service, allowing buses to quickly exit the highway, allow passengers to board and alight, and then return to the highway. By enabling line-haul express buses to serve passengers at highway interchanges, HITODs will create the transfer interface for feeder modes such as local buses, Kiss-and-Ride, Park-and-Ride, bicycle, taxi and pedestrian that heretofore has been missing from suburban highway interchanges. Second, a HITOD integrates developable space within the area of interchange itself, which allows the development to be easily accessed by the surrounding neighborhood. Combined with Traditional Neighborhood Design principles, HITODs could potentially create a highway equivalent to the “string of pearls” pattern of land development established more than a century ago by early American railroad companies.  This paper describes a prototype HITOD and makes other suggestions for future research.]]></description>
      <pubDate>Thu, 28 Apr 2011 07:01:11 GMT</pubDate>
      <guid>https://trid.trb.org/View/1091531</guid>
    </item>
    <item>
      <title>Random Utility Approach to Re-Designing the Passengers Interchange Node</title>
      <link>https://trid.trb.org/View/898765</link>
      <description><![CDATA[The passengers interchange node is a complex infrastructure where the user can choose among different modal options for his/her trip. These transport infrastructures have various terminals (car park, bus stop, metro, light rail, railway, extra-urban and sub urban bus and so on). The passengers inside the interchange node have to reach these terminals, often walking with luggage and for long distances. The authors calibrated a discrete choice model taking into account attributes that are able to explain passenger behavior by observed flows and the generalized least squares technique. Furthermore, an ex ante/ex post analysis was carried out in order to design and evaluate measures for incentive modal integration, improving perceived quality and transfer facilities in the walking path.]]></description>
      <pubDate>Fri, 14 Aug 2009 06:47:50 GMT</pubDate>
      <guid>https://trid.trb.org/View/898765</guid>
    </item>
    <item>
      <title>A Predictive Model of Highway Interchange Land Use Development: A Decision Tool for Planning</title>
      <link>https://trid.trb.org/View/843860</link>
      <description><![CDATA[This paper develops a method for predicting the economic development that is likely to occur at a given interchange site. The goal is to identify the interrelationships among the important factors that lead to interchange development and to provide planners with a guide for estimating the potential development of non-urban interchange areas. Knowing the probable level of interchange area development, state and local planners can then prepare a reasonable land use plan for the interchange. Design engineers can, in turn, proceed to determine the highway capacity requirements, geometric configurations and traffic control needs. With an accurate development forecast, the highway design and land use plan can be coordinated to encourage desirable and efficient development, while at the same time facilitating both traffic flow and safety and reducing the probability of premature obsolescence.]]></description>
      <pubDate>Mon, 28 Jan 2008 08:14:57 GMT</pubDate>
      <guid>https://trid.trb.org/View/843860</guid>
    </item>
    <item>
      <title>New Chapter 26 for the Highway Capacity Manual: "Interchange Ramp Terminals"</title>
      <link>https://trid.trb.org/View/811769</link>
      <description><![CDATA[Diamond interchanges, partial cloverleaf interchanges and single point urban interchanges have been basic freeway design since freeways were first constructed.  However, until recently, no accepted methodology was available to help reviewing agencies know whether or not the interchange operations analyses presented to them were reliable.  In a newly approved chapter of the Highway Capacity Manual, a procedure has been developed to analyze these interchanges.  The new chapter incorporates characteristics that are unique to interchanges and includes:  redefining levels of service A to F to better reflect the types of delays encountered at interchanges; origin-destination characteristics of turning movements at interchanges; operational effects of intersection spacing; lane utilization for both through and turning movements at an interchange; demand starvation; and interchange type selection analysis to help determine the impacts of changing interchange types.  Two types of analyses for signalized interchanges are supported in the new chapter: final design and operational analysis.]]></description>
      <pubDate>Fri, 20 Jul 2007 09:53:44 GMT</pubDate>
      <guid>https://trid.trb.org/View/811769</guid>
    </item>
    <item>
      <title>Comparing the Operations of the Freeway-to-Freeway W-Interchange Designs to Other Freeway-to-Freeway Conventional Designs</title>
      <link>https://trid.trb.org/View/793080</link>
      <description><![CDATA[As traffic volumes increase, traffic congestion is becoming a problem at many urban interchanges in high growth areas. A new interchange design, called the W-interchange (WI), seeks to reduce congestion at a reasonable cost. The freeway-to-freeway design looks to reduce the impacts to the freeway vehicles as other vehicles merge and diverge from the freeway. The purpose of this paper is to compare two different W-interchange designs to more commonly used designs for freeway-to-freeway interchanges, specifically the Full Clover Leaf interchange (FCI) and the Four Level interchange (FLI). The W-interchange design utilizes less right-of-way (ROW) than other freeway-to-freeway interchanges, but has more weaving sections. Both W-interchange designs use four bridges to move traffic, including two bridges to cross the freeways. This presentation seeks to compare total times through the different designs using a microscopic traffic simulation package and quantify impacts to the freeways. The two W-interchange designs showed to have a lower total time through the network and a higher average speed than the two conventional interchanges. Since the W-interchanges performed better than the other two interchanges with respect to total time and average speed, the interchanges need further study to see how they compare overall, including construction and maintenance costs. The W-interchange designs are best for a new facility or interchange, but an existing interchange could be retrofitted if there is sufficient spacing between the upstream and downstream interchanges.]]></description>
      <pubDate>Wed, 15 Nov 2006 16:21:55 GMT</pubDate>
      <guid>https://trid.trb.org/View/793080</guid>
    </item>
    <item>
      <title>Hybrid Interchanges: Developing the Arterial of the Future</title>
      <link>https://trid.trb.org/View/760456</link>
      <description><![CDATA[Urban arterial roadways are one of the most important facilities provided for the public. To be beneficial, they should be designed to move high volumes of traffic safely at reasonable speeds and provide needed access to businesses and residences. This is the challenge roadway designers have before them. The ultimate goal of arterial design has been to develop a facility that will do all those things, do them well, and do them at a reasonable cost. The ideas presented in this paper suggest that this goal may be nearing fulfillment.  The weak point of arterial design (or the linchpin, depending on the perspective) has been the arterial/arterial intersection. Extremely high volumes, both through and turning, come together at the same point at the same time, and all of these substantial traffic demands need to be served in the best manner we know how. Because of these conflicting needs, intersections have served as bottlenecks to the flow on arterial roadways, providing only 30-50% of the capacity available on the arterial itself. To improve arterial intersections, a widened intersection with turn lanes has typically been provided, controlled by a traffic signal. The alternative to this has been the consideration of a grade-separated interchange. For a congested arterial/arterial intersection, the at-grade solution has typically been too little, while the grade-separated solution has typically been too much. What follows is a concept that the authors hope practitioners see as a method for improving operational efficiency and utilizing untapped capacity on arterials.]]></description>
      <pubDate>Wed, 21 Sep 2005 13:14:24 GMT</pubDate>
      <guid>https://trid.trb.org/View/760456</guid>
    </item>
    <item>
      <title>Some Guidelines for Selecting Microsimulation Models for Interchange Traffic Operational Analysis</title>
      <link>https://trid.trb.org/View/758225</link>
      <description><![CDATA[There are several commercially available traffic simulation packages that are able to model the full range of interchange ramp terminals. Each of these packages has pros and cons for simulating various types of interchanges and traffic control plans. Previous research has studied specific simulators in terms of their capabilities for simulating single urban point interchanges (SPUIs) and diamond interchanges. There is no guidance provided however on how to generally select appropriate simulators based on their capabilities and internal algorithms for analyzing specific interchange design and control scenarios. This paper focuses on identifying the elements that should be available in a simulator in order to evaluate a specific interchange scenario (including type, geometry, and traffic control characteristics). The paper does not identify all the specific packages that are appropriate for a specific scenario because these evolve constantly; even though the current version of a package may not support a particular function, future versions of that package may incorporate it. Thus, identifying the most appropriate package would very quickly become obsolete. It is up to the analyst to examine whether a particular characteristic or algorithm is present in a specific package. To accomplish this, three simulators were selected and studied: AIMSUN, CORSIM, and VISSIM. Data from two interchanges (one SPUI and one diamond interchange) at Arizona were obtained and used in the assessment of these packages. The model parameters and assumptions are examined for each model. Simulation is conducted first by using default parameter values followed by a calibration process to adjust parameters related to driver behavior, vehicle performance, and others. In conclusion, several elements are identified as critical in simulating interchanges, which fall in the following categories: (1) the capability of representation of specific geometric characteristics; (2) the capability of simulating specific signal control plans; (3) calibration needs and accuracy in comparison to field conditions; (4) the extraction of specific performance measures from the simulator; and (5) other observations from the research.]]></description>
      <pubDate>Wed, 20 Jul 2005 09:14:11 GMT</pubDate>
      <guid>https://trid.trb.org/View/758225</guid>
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