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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>
    <image>
      <title>Transport Research International Documentation (TRID)</title>
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      <link>https://trid.trb.org/</link>
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    <item>
      <title>A Mixed Method Approach for Modelling Entry Capacity at Rotary Intersections</title>
      <link>https://trid.trb.org/View/2592176</link>
      <description><![CDATA[Rotary intersections, known as old traffic circles, require vehicles entering from branches to yield to circulating traffic. Upon entering, vehicles travel around a central island and exit toward their desired branch, generating merging and diverging conflicts at entry and exit points. Rotary capacity models are focused on the weaving manoeuvres within the circular roadway sections, associating capacity with the maximum traffic flow rate of each weaving segment. This paper introduces a novel approach combining modern roundabouts capacity models with the old rotary ones. In particular, the present study proposes a mixed approach based on an iterative process that combines the English TRRL model, which is suited for the old rotaries and based on short weaving sections capacity, with the features of the HCM-7th entry capacity model of the modern roundabouts, which is based on the circulating-traffic priority rule. Such an approach is rooted in the total capacity criteria and traffic conditions where all roundabout entrances reach congestion simultaneously. Compared to the past, this new approach makes entry performance estimation, such as average delay and queue length, bridging the gap between outdated and current methodologies in the field of rotary intersection design and assessment.]]></description>
      <pubDate>Fri, 14 Nov 2025 14:37:04 GMT</pubDate>
      <guid>https://trid.trb.org/View/2592176</guid>
    </item>
    <item>
      <title>Traffic Circles: Their Past, Present, and Future</title>
      <link>https://trid.trb.org/View/2539836</link>
      <description><![CDATA[This discussion of traffic circles covers the purposes for which they were first used, how they have evolved over time, and the many and varied purposes for which they continue to be used. The article concludes that current research studies directed toward the improvement of the neighborhood street environment confirm that the rotary concept can be an asset in restricting the use of residential streets and roads, and if this type of application becomes common, the traffic circle will then have returned to its original historic purpose - discouraging the intrusion of unwelcome visitors.]]></description>
      <pubDate>Tue, 22 Apr 2025 11:29:58 GMT</pubDate>
      <guid>https://trid.trb.org/View/2539836</guid>
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    <item>
      <title>The Traffic Information Collection and Transmission on Full-Scale Ring Road for Accelerated Loading Test</title>
      <link>https://trid.trb.org/View/2000500</link>
      <description><![CDATA[The full-scale ring road (full-scale track) accelerated loading test system can be considered as a closed ITS. The traffic information collection and transmission are very important for the traffic control, especially for test safety and efficiency. This paper shows the key processes of the system design and implementation about the traffic information collection and transmission on full-scale ring road for accelerated loading test. Firstly, the authors select the scope of traffic information, including vehicles and road information, which is closely related to the test control. Secondly, the information is classified, and the engineering implement methods of traffic information collection and transmission are studied as well. At this stage, equipment capacity and transmission network structure need to be considered. Finally, the system construction needed to be completed in next few months. In current phase, the authors have already started to the debug scheme, including the research of difficulties in debugging and corresponding solutions.]]></description>
      <pubDate>Mon, 27 Mar 2023 15:09:24 GMT</pubDate>
      <guid>https://trid.trb.org/View/2000500</guid>
    </item>
    <item>
      <title>Capacity Analysis of Signalized Traffic Circles in Comparison with Conventional Intersections</title>
      <link>https://trid.trb.org/View/1987982</link>
      <description><![CDATA[Full signalized traffic circles are operating in some countries to serve the heavy turning traffic flows at large-sized road junctions. Their capacities are influenced by many factors, such as the traffic conditions, signal control types and geometric layouts. The objective of this study is to find out the specified traffic demand conditions that signalized traffic circles are preferred in different cases of the number of lanes and lane configurations. A signal optimization model for the traffic circles is proposed for investigating five cases of signalized traffic circles under various traffic demand conditions. The results showed that signalized traffic circles have higher capacity than signalized intersections in some specific cases, e.g. when the total number of approach lanes reaches five or when more than one right-turn lanes are required. Besides, an analysis on the relationship between the capacity and the occupied area is conducted to further consider the geometric influence.]]></description>
      <pubDate>Thu, 18 Aug 2022 11:30:27 GMT</pubDate>
      <guid>https://trid.trb.org/View/1987982</guid>
    </item>
    <item>
      <title>Racing line optimisation for an advanced driver assistance system</title>
      <link>https://trid.trb.org/View/1898172</link>
      <description><![CDATA[This paper deals with an accurate, robust and efficient optimization method for time optimal path planning on circular tracks. Starting with a general description of the problem, suitable method domains for time-optimal path planning are qualified. In terms of reproducibility and accuracy, the authors propose an algorithm combining a model- and a policy-based method which takes car, track and driving data gathered from connected cars into account. Hence, it can provide a consistently learning as well as a sufficient constant time-optimal racing line on worldwide race tracks for different driver assistance purposes. The authors evaluated the calculated racing lines with respect to heuristic criteria like curve cutting behavior and by comparing them to ones driven by professional race drivers.]]></description>
      <pubDate>Wed, 29 Dec 2021 10:52:16 GMT</pubDate>
      <guid>https://trid.trb.org/View/1898172</guid>
    </item>
    <item>
      <title>Transpolis Flexity: A Platform for Connected and Autonomous Mobility Operated Both by Public and Private Research Sectors</title>
      <link>https://trid.trb.org/View/1736809</link>
      <description><![CDATA[The growth in urban transport needs now far exceeds the development of transport infrastructure. To date, very little work has been done on how to integrate technical, economic, social and political considerations to create a sustainable mobility system that meets the needs of a changing world. New approaches to mobility as a whole are needed to improve the dialogue between infrastructure and vehicles. Faced with this situation, IFSTTAR and the CARA competitiveness cluster (European Cluster for Mobility Solutions) operating in the transport of goods and people responded to the call for projects of the French State's Investment Plan for the Future by proposing the TRANSPOLIS FLEXITY project, which was labelled as a shared innovation platform in 2012. This 80-ha test and experimentation platform located near Lyon in the Ain plain is the result of a €18 million public/private investment (Auvergne Rhône Alpes Region, Lyon Metropolitan Area, Ain Department, Communauté de Communes de la Plaine de l'Ain, Ministry of Higher Education, Research and Innovation, Ministry of Finance, IFSTTAR and several companies). It proposes to achieve the threefold objective of carrying out the research activities that are still missing, developing pre-operational projects and approving products and systems, at the interface between connected or autonomous vehicles, infrastructure and society, through the implementation of tests and phases of controlled environment testing. A 2.2 km 3-lane ring road, two orthogonal urban boulevards 800 and 600m long and 20m wide, 5 km of streets, 6 km of interurban roads, a dedicated ADAS track, 1000m long and 25m wide, dedicated to connected and autonomous vehicles (CAV), crash-test tracks compose a unique set of test facilities allowing a systemic approach to problems for researchers and engineers. The four areas addressed by the platform in this holistic system are infrastructure, vehicle, user and mobility operator. IFSTTAR developed the design of this platform through extensive upstream work involving its research teams and private sector engineers.]]></description>
      <pubDate>Tue, 29 Sep 2020 11:19:57 GMT</pubDate>
      <guid>https://trid.trb.org/View/1736809</guid>
    </item>
    <item>
      <title>Determinations of Critical Gap and Follow-up Time at Roundabouts in Jordan</title>
      <link>https://trid.trb.org/View/1659700</link>
      <description><![CDATA[Critical gap and follow-up times are two important fundamental traffic parameters used in the design and operational analysis of roundabouts and un-signalized intersections. Moreover, they are used to assess capacity and level of service at minor roads. In Jordan, roundabouts are used extensively, and therefore, there is a need to conduct studies on follow-up and critical gap time. The driver behaviour in Jordan can be described as aggressive in terms of their choice of follow-up headway at roundabouts. In this study, the roundabouts were located in mountainous terrain which allowed the collection of critical gap observations for approach slopes ranging from 6% up to 8%. The critical gap and follow-up times were recorded and analyzed. This research also identified other factors affecting critical gap, lag and follow-up times such as geometry of roundabout, slope of the approach, culture and behaviour of drivers. This research also proposes a significant relationship between approach slope at roundabouts and the observed gap. This relationship may be incorporated in the estimation of capacity and level of service determination at roundabouts. The results of this study should assist highway and traffic designers in the design and the performance evaluation of roundabouts.]]></description>
      <pubDate>Tue, 22 Oct 2019 16:49:47 GMT</pubDate>
      <guid>https://trid.trb.org/View/1659700</guid>
    </item>
    <item>
      <title>Hybrid Signal Priority and Full Actuation for Isolated Large Four-Leg Circular Intersections</title>
      <link>https://trid.trb.org/View/1639207</link>
      <description><![CDATA[In cities with bus rapid transit (BRT) systems, median bus-only lanes (MBLs) may extend to a circular intersection of two arterials. Making the MBLs traverse the central island is advantageous to BRT vehicles with less damage to the aesthetic advantage of the circular intersection. Hybrid signal priority and full actuation (HySOFA) is developed for isolated large four-leg circular intersections with MBLs. The objective of HySOFA is to expedite the operating speed of BRT vehicles with little negative impact on general vehicles. With appropriate application of transit and traffic facilities, the central island is traversable to BRT vehicles and the right-of-way is assigned in an upgraded version of the concurrent entering mode. Traffic detectors are placed at specific positions to detect BRT vehicle arrivals and sense general vehicle demand. Signals for general vehicles are fully actuated. Green extension, early green, and phase insertion are incorporated into the fully actuated logic. According to the simulation results during peak periods, HySOFA was quite effective in reducing the delay and number of stops for BRT vehicles at the circular intersection. The resulting cost to general vehicles was not large. After implementation of HySOFA, the circular intersection outperformed its conventional intersection alternative in serving general vehicles and pedestrians with less delay. BRT vehicles would not perceive substantially less delay and number of stops at the conventional intersection than at the circular intersection. When the MBLs extended to a large four-leg circular intersection, it would be a sensible decision for traffic engineers to make traffic improvements on the circular intersection instead of converting it to a conventional intersection.]]></description>
      <pubDate>Tue, 22 Oct 2019 14:42:32 GMT</pubDate>
      <guid>https://trid.trb.org/View/1639207</guid>
    </item>
    <item>
      <title>Evaluating fracture properties of crumb rubber modified asphalt mixes</title>
      <link>https://trid.trb.org/View/1648620</link>
      <description><![CDATA[Discarded vehicle tires pose a severe environmental problem in the United States. Incorporating shredded tire rubber as crumb rubber modifier (CRM) into asphalt paving materials has shown potential for great benefits. This study was undertaken to evaluate the effect of CRM, base virgin binder stiffness, total binder content, and aggregate gradation on fracture performance of CRM asphalt mixes using the semi-circular bend (SCB) fracture test. All mixes were long term oven aged (LTOA) before testing at the effective temperature for cracking resistance. The results were analyzed within the context of several response parameters: a modified version of Illinois flexibility index (FI), fracture energy, and the load at failure (peak load). Fracture performance of virgin and CRM binders were also evaluated using linear amplitude sweep (LAS) test and the Glover-Rowe (G-R) parameter obtained from dynamic shear rheometer (DSR). As expected, adding CRM into asphalt mixes increased the design binder content. In addition, design binder content increased as the CRM content increased in the mix. Fracture test results showed that among dense graded mixes, CRM mixes with the highest binder content showed superior flexibility and cracking resistance compared with those with lower binder content, in spite of the fact that CRM mixes delivered lower peak load (i.e. strength). It was also shown through this study that gap graded CRM mixes are preferred to dense graded CRM mixes as they deliver higher flexibility thus better cracking resistance. Finally, results from the binder tests demonstrated superior cracking resistance of CRM binders compared with virgin binders.]]></description>
      <pubDate>Mon, 09 Sep 2019 15:06:40 GMT</pubDate>
      <guid>https://trid.trb.org/View/1648620</guid>
    </item>
    <item>
      <title>Upgrading traffic circles to modern roundabouts to improve safety and efficiency – Case studies from Italy</title>
      <link>https://trid.trb.org/View/1593570</link>
      <description><![CDATA[This paper presents a procedure for analysing safety and operational improvements made possible by converting traffic circles to modern roundabouts. An Italian case study is presented for alternative layouts under various traffic demand scenarios. In the application of the procedure, the average waiting times and queue lengths at entries are computed with an analytical capacity model, using default values for gap parameters. Then, the roundabout is dynamically simulated. The simulation results in a revised set of gap parameters that are in turn used as inputs to a second trial of the capacity model, and in turn fed back into the simulation. The two steps are repeated until the parameters reach a pre-selected convergence criterion, so that gap parameter values for both the static capacity and dynamic microsimulation models are in equilibrium. Therefore, the applied procedure can conduct both static and dynamic roundabout design, usually applied separately. One can start with default values in guidelines and couple them with limited field data, improving both the expected results and cost-effectiveness of solutions. Next, safety is estimated using dynamic simulation software and a compatible conflict counting model to acquire surrogate measures of safety. Level-of-service and surrogate safety indicators for the existing and redesigned roundabouts are then compared. The procedure is first demonstrated on an old “ultra-large” roundabout. The procedure is tested on this roundabout using the Highway Capacity Manual 2016 (HCM2016), AimsunTM, and Surrogate Safety Assessment Model (SSAM) software. A redesign is shown to be far superior in efficiency and safety. Finally, two cases are described where large first generation roundabouts were upgraded to modern standards.]]></description>
      <pubDate>Fri, 07 Jun 2019 17:29:04 GMT</pubDate>
      <guid>https://trid.trb.org/View/1593570</guid>
    </item>
    <item>
      <title>Contribution to pavement friction modelling: an introduction of the wetting effect</title>
      <link>https://trid.trb.org/View/1626913</link>
      <description><![CDATA[This paper presents a friction model describing the tyre rubber/road interaction that takes into account the viscoelasticity of the tyre rubber, the texture of the road surface and a water layer between the tyre/road interface by introducing explicitly a computation of the water layer effect in the calculation process of the hysteretic friction. The geometry of the wetted portion of the interface model is simplified by transforming it into an equivalent hydrodynamic bearing. Utilising the Reynolds equation, the bearing load capacity is calculated and the resulting forces are subtracted from the contact load when calculating the forces of the hysteretic friction. The mechanical behaviour of the rubber is represented in the model by Kelvin–Voigt model. The frictional forces due to hysteresis are calculated at any given operating conditions (load, slip speed, etc.) from the contact geometry of rough surfaces caused by the viscoelastic behaviour of rubber. To validate the model, a set of surfaces including real pavements and artificially textured slabs were selected covering a wide range of microtexture and macrotexture combinations and the computed and measured friction compared. To describe the contact geometry of rough surfaces using macrotexture and to measure actual friction, the Circular Track Meter and the Dynamic Friction Tester devices were used, respectively. The friction coefficients computed using the model were compared to the measured friction coefficients. The obtained results are presented in the paper and proved to provide high correlation between the measured and modelled friction. The model is capable to predict wet friction at low as well as high speeds on wet surfaces, thus proving to be capable to take adequately the wetting effect on the variation of friction with increasing speed. Recommendations are provided to improve the model and extend it to a tyre friction model.]]></description>
      <pubDate>Wed, 05 Jun 2019 12:53:41 GMT</pubDate>
      <guid>https://trid.trb.org/View/1626913</guid>
    </item>
    <item>
      <title>Effect of Testing Configuration in Semi-Circular Bending Fracture of Asphalt Mixtures: Experiments and Statistical Analyses</title>
      <link>https://trid.trb.org/View/1590707</link>
      <description><![CDATA[The semi-circular bending (SCB) test is a simple, efficient, and easily applicable method in the pavement community to characterize fracture behavior. This makes it widely used as a quality control (QC) and quality assurance (QA) approach at several transportation agencies. However, public–private testing laboratories have implemented SCB test methods using different load-support fixture conditions with an insufficient understanding of how the conditions affect the results and testing variability. This could be particularly problematic when using SCB test results obtained from different load-support fixtures as QC–QA (or pass/fail) purposes. This study investigated the effect of SCB testing configurations on test results and their variability by conducting tests using six different load-support fixtures. Several fracture-related indicators such as fracture energy, flexibility index, peak load, and the coefficient of the cracking index resulting from the six different load-support fixtures were compared. Test results and statistical analyses showed that SCB tests generally showed repeatable results, whereas load-support fixtures can affect test results and their repeatability, thus care should be taken when choosing a testing fixture. The addition of roller springs generally increased the variability of the test results. It appears that the mid-span jig was detrimental to testing repeatability, and friction at the support should be avoided because it can erroneously increase fracture resistance with a higher variability.]]></description>
      <pubDate>Tue, 09 Apr 2019 09:37:55 GMT</pubDate>
      <guid>https://trid.trb.org/View/1590707</guid>
    </item>
    <item>
      <title>Experimental Investigation on Fatigue and Low Temperature Properties of Asphalt Mixtures Designed with Reclaimed Asphalt Pavement and Taconite Aggregate</title>
      <link>https://trid.trb.org/View/1583904</link>
      <description><![CDATA[Using reclaimed asphalt material for rehabilitation and construction of new asphalt pavements is currently a common practice not only in view of the economic benefits associated with this process but also because of the reduced exploitation of natural resources. For this reason, road authorities have implemented recommendations and guidelines to regulate the use of reclaimed asphalt pavement (RAP) and other recycled materials such as industrial by-products. Nevertheless, the combined use of different recycled materials is not commonly addressed. In this paper, the effect of adding RAP and taconite (a mining by-product) on fatigue and low temperature properties of asphalt mixture was investigated with two different testing geometries: indirect tensile (IDT) and semi-circular bending (SCB). Fatigue behavior, creep stiffness, relaxation modulus, low temperature fracture energy, and fracture toughness were also evaluated, computed, and then compared. A more brittle behavior was observed for mixture prepared with RAP material, however, the mechanical performance was not significantly different for mixtures containing 20% RAP alone and in combination with 50% taconite compared with conventional asphalt mixtures designed with virgin material. This was not the case when RAP content was increased up to 50%, showing a substantially poorer response both in terms of fatigue and low temperature characteristics and suggesting the RAP had a dominant effect. The present exploratory research seems to support the idea of combining RAP and different industry by-products, such as taconite, as long as the RAP content is kept below a specific threshold.]]></description>
      <pubDate>Fri, 15 Mar 2019 14:56:08 GMT</pubDate>
      <guid>https://trid.trb.org/View/1583904</guid>
    </item>
    <item>
      <title>Long Term Material Properties of Field Semi-Rigid Base</title>
      <link>https://trid.trb.org/View/1572567</link>
      <description><![CDATA[This paper presented an extensive study on the long term strength development and fatigue property of 5-15 years old pavement semi-rigid base. 145 cores were taken from 5 expressways in Jiangsu, China to evaluate the long term mechanical properties of semi-rigid base. The deflection basin test results showed that the stiffness of 15 years old cement treated base showed increasing trend while the lime and fly ash treated base did not. Strong linear relationships were found among unconfined compressive strength, the semi-circle bending (SCB) strength and the compressive resilient modulus. Strength test results showed that the strength of cement treated materials were higher than those of lime and fly ash treated ones. In addition, the strength of cement treated base showed increasing up to 15 years while the strength of lime and fly ash treated base in the drive lane showed decreasing trend between 16 to 18 years. The SCB fatigue test of the cores showed that cement treated base also had much higher fatigue life than lime and fly ash treated ones. The SCB and beam fatigue tests failed faster than the indirect tensile fatigue tests and are more sensitive to stress level. The fatigue life of CTB increases dramatically as the decrease of stress ratio and therefore CTB could be a long life structure when the stress level is controlled at a lower level. The crack propagation pattern showed that fracture tends to occur along the side of aggregates, indicating a relatively weak aggregate-cement mortar interface, which is worth further investigation to evaluate the cracking behavior of semi-rigid base.]]></description>
      <pubDate>Sat, 02 Mar 2019 15:41:13 GMT</pubDate>
      <guid>https://trid.trb.org/View/1572567</guid>
    </item>
    <item>
      <title>Laboratory Evaluation of Foamed Asphalt Mixtures Containing 100% RAP and Rejuvenator: Georgia's Experience</title>
      <link>https://trid.trb.org/View/1572860</link>
      <description><![CDATA[A research project on cold asphalt recycling with foamed asphalt was recently completed using 100% Reclaimed Asphalt Pavement (RAP) containing rejuvenator in the state of Georgia. The research aimed to see the impact of rejuvenator on 100% RAP foamed asphalt mixtures and assess the feasibility of using the mix as a base layer. This paper presents a part of the research findings, specifically focusing on the performance of 100% RAP foamed asphalt mixtures with and without rejuvenator through three laboratory tests: Marshall Stability (MS), Indirect Tensile Strength (ITS), and Semi-Circular Bending (SCB). Three rejuvenator dosage levels (6%, 12%, and 18%) were pre-determined based on asphalt viscosity (G*/sin δ) of extracted RAP asphalt. The test results indicate that the MS and ITS of the mixtures without rejuvenator are reasonably high enough to be used as a base layer. However, when a 6% or more rejuvenator is dosed in the mixtures, the MS and ITS significantly decrease. The fracture resistance at an intermediate temperature measured by the SCB tests indicates that the mixtures without rejuvenator are more brittle than conventional Hot Mix Asphalt (HMA). When a 6% or more rejuvenator is added, the Flexibility Index (FI) shows that the mixtures become more crack-resistible than both HMA and no-rejuvenator 100% RAP foamed asphalt mixtures. It is concluded that the impact of rejuvenator on the structural integrity of the 100% RAP foamed asphalt mixtures is significant; it helps increase the cracking resistance, but considerably decreases the stability and indirect strength.]]></description>
      <pubDate>Sat, 02 Mar 2019 15:41:12 GMT</pubDate>
      <guid>https://trid.trb.org/View/1572860</guid>
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