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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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      <title>Passenger vehicle tyre aerodynamics</title>
      <link>https://trid.trb.org/View/2491309</link>
      <description><![CDATA[Road vehicles are an essential part of society, enabling the movement of people and goods. They are, however, responsible for a large part of greenhouse gas emissions. Therefore, automotive companies strive to constantly increase the energy efficiency of their fleets. For cars, aerodynamic drag is one of the main resistive forces and a substantial part of the total energy consumption. A significant contribution to the total drag originates from the wheels, making the understanding of their flows essential for creating efficient vehicles. Factors such as the wheels' rotation, bluff-body shape and small geometrical details result in complex flow fields that are sensitive to, for example, wind tunnel setup, vehicle velocity and small geometrical changes. Due to this sensitivity, the experimental and numerical methods used to assess wheel aerodynamics should be carefully evaluated. Full-scale wind tunnel tests are compared to simulations with an open road domain and with adomain containing a detailed model of the wind tunnel. Including the wind tunnel improves the prediction of both absolute drag values and the drag delta between configurations. The importance of considering the parasitic lift acting on the wheel drive units (WDUs) of thewind tunnel is also evaluated. In the second part of the thesis, the effects of various geometrical tyre features and their impacton the total drag and flow field around the vehicle are considered.]]></description>
      <pubDate>Fri, 17 Jan 2025 15:18:21 GMT</pubDate>
      <guid>https://trid.trb.org/View/2491309</guid>
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    <item>
      <title>Hydroplaning: preparing today for tomorrow’s downpours</title>
      <link>https://trid.trb.org/View/2441533</link>
      <description><![CDATA[Hydroplaning is a phenomenon that can occur on wet roads where a motorised vehicle’s speed is such that tyres begin to rise up over the water film similar to water skis, resulting in the loss of frictional forces between the tyres and road and hence loss of vehicle control. Given Australia’s east coast recent large rain downpours and flooding and New Zealand’s expected future extreme rainfalls, it may now be timely to review Australia’s and New Zealand’s vehicle roadworthy laws concerning minimum tyre tread depth of 1.5 mm and the need for in-vehicle tyre pressure monitoring systems. This article discusses the relationship between tread depth and critical speed identifying when hydroplaning occurs. Two fatal injury vehicle crash case examples are discussed to illustrate the concern. Increasing minimum tread depth for roadworthiness compliance and automatic tyre pressure monitoring are recommended based on this study.]]></description>
      <pubDate>Tue, 15 Oct 2024 13:32:41 GMT</pubDate>
      <guid>https://trid.trb.org/View/2441533</guid>
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    <item>
      <title>Optimising tyre wear and exploring its conflict with comfort</title>
      <link>https://trid.trb.org/View/2093197</link>
      <description><![CDATA[The automotive industry is shifting its focus on energy efficient driving to tackle rising environmental issues. In this direction, as exhaust particle emissions continuously decrease, the attention is turned on non-exhaust traffic related sources in ground vehicles, such as the interaction between tyre and roads and the tyre wear. Given that the tyres are costly for the vehicle owner and wear creates large waste of old tyres, the modelling and the minimisation of tyre wear have been of great interest recently. The tyre wear is mainly caused by inner (tyre structure and shape) and external (suspension configuration, speed, road surface, etc.) factors. So, this work presents a sensitivity analysis of both inner and external factors, and then explores the optimisation of tyre and suspension parameters for minimising tyre wear and enhancing comfort. More specifically, initially the inner factors are investigated regarding their impact on tyre wear, while external factors, i.e., vehicle loading, velocity and road type, which can be different daily regarding the purpose of the ride, are studied regarding both comfort and tyre wear outlining the conflicting relation between these two objectives. Finally, informed by the results, the optimum tyre and suspension design for a passenger vehicle are sought to both minimise tyre wear, enhance comfort and improve vehicle stability in normal loading conditions while the vehicle drives in a city road (Road Class A) with normal speed.]]></description>
      <pubDate>Tue, 03 Jan 2023 14:20:55 GMT</pubDate>
      <guid>https://trid.trb.org/View/2093197</guid>
    </item>
    <item>
      <title>Tyre aerodynamics of passenger vehicles</title>
      <link>https://trid.trb.org/View/2075197</link>
      <description><![CDATA[To decelerate climate change and limit global warming, there is a need for reducing the environmental impact of vehicles, which can be achieved by increasing their energy efficiency. For a passenger vehicle, one of the largest resistive forces is aerodynamic drag. A significant contribution to the total drag originates from the wheels, making the understanding of their flows essential for creating efficient vehicles. However, wheel flows are complex and challenging to comprehend due to factors such as the rotation, high level of geometrical details and tyre deformation, all of which have been shown to affect drag. For a better understanding, numerical simulations can be used. However, to determine the accuracy of the simulations, these must be correlated to experiments. In this work, both the correlation between experiments and simulations as well as the flow field effect of varying the tyre tread pattern are investigated. Wind tunnel tests using a full-scale DrivAer model have been performed for four tyre tread patterns and two rim designs. First, the numerical simulations are compared to the experiments, where the interference of the wind tunnel on wheel flows is investigated. By performing simulations using both an open road domain and a domain containing a detailed model of the wind tunnel, it was found that the inclusion of the wind tunnel improves predictions of both absolute drag values as well as the drag deltas between configurations. Then, the effects of the different tyre tread patterns are analysed in more detail. Results showed that adding rain grooves typically reduces drag compared to a slick tyre, whereas the effect of lateral grooves is dependent on the rim configuration. In addition to the drag, lift variations were considered. There, the largest effects were obtained at the front axle and, in general, the lift is reduced by the rain grooves and increased by the lateral grooves, most clearly for the closed rim. Also, the influence of the parasitic lift forces acting on the wheel drive units was demonstrated.]]></description>
      <pubDate>Fri, 02 Dec 2022 11:40:50 GMT</pubDate>
      <guid>https://trid.trb.org/View/2075197</guid>
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    <item>
      <title>Chemical leaching from tire wear particles with various treadwear ratings</title>
      <link>https://trid.trb.org/View/1987544</link>
      <description><![CDATA[]]></description>
      <pubDate>Thu, 30 Jun 2022 11:57:48 GMT</pubDate>
      <guid>https://trid.trb.org/View/1987544</guid>
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    <item>
      <title>Tyre/road interaction : a holistic approach to the functional requirements of road surfaces regarding noise and rolling resistance</title>
      <link>https://trid.trb.org/View/1737819</link>
      <description><![CDATA[Increased fuel consumption, increased greenhouse gas emission, diminishing real-estate prices and increased health issues are some of  the negative effects on the climate, on the environment and on the society from tyre/road rolling resistance and noise. The first two aspects are affected by energy dissipation in the tyre/pavement contact and are related to rolling resistance. The other two aspects, real-estate property prices and health and comfort issues, are related to noise. This thesis uses a holistic approach to analyse functional properties of the tyre/road contact interaction. It studies how measures taken for different functional properties may correlate and studies the limits in evaluation of mitigation strategies considering the precision in available measurement methods. The investigative work included an examination of how reproducible CPX measurements are for evaluating tyre/road noise. Furthermore, the procedure for rubber hardness correction was subjected to a specific evaluation. Noise and rolling resistance measurements were performed on drums and the results were compared to on-road measurements for 50 different tyre models. Additionally, the consistency of rolling resistance measurements on roads was evaluated. Two mitigation strategies are discussed in this thesis: (i) selection of tyres, and (ii) grinding of road surfaces. For the first strategy, more than 600 CPX and more than 500 rolling resistance measurements were carried out with 50 different tyre models to evaluate potential gain in selecting the best tyres. For the second strategy 8 road sections were ground and the effect of grinding was evaluated with respect to noise and rolling resistance. The results indicate that when the CPX method is performed correctly, it can consistently evaluate tyre/road noise. Recommendations on how uncertainty in the CPX method can be reduced are included in the thesis. Additionally, recommendations on how the tyre rubber hardness measurements can be improved are also discussed, which is relevant not only for noise measurements but also for rolling resistance measurements. The selection of tyres is the mitigation strategy that has the largest potential to reduce noise and rolling resistance, yet it can take time to be implemented. On the other hand, surface grinding leads to substantial noise and rolling resistance reductions and can more readily be implemented. Noise and rolling resistance measurements on roads were compared to measurements on drums and no correlation was found. This indicates that drum results cannot be directly compared to tyre performances on roads. Values presented on the EU tyre lables were shown to not correlate to on-road measurements; this calls for a re-examination of the tyre labelling procedures. Regarding labelling of road surfaces, results in this thesis indicate that reliable acoustical properties can be obtained with the CPX method in a reproducible way and suggests that acoustical labelling of road surfaces is feasible with a precision of 1 dB.]]></description>
      <pubDate>Tue, 08 Sep 2020 14:38:07 GMT</pubDate>
      <guid>https://trid.trb.org/View/1737819</guid>
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    <item>
      <title>Mönsterdjupets inverkan på väggrepp på is för släpvagnsdäck till tunga fordon: jämförande tester</title>
      <link>https://trid.trb.org/View/1696257</link>
      <description><![CDATA[In Sweden the current regulation for minimum tread depth for heavy vehicles in the winter period is different for trailer axles compared to drive or steer axles. While the requirement for the latter axles are 5 mm tread depth, on trailer axles 1,6 mm is required. The purpose of this study has been to investigate whether there is reason to increase the tread depth requirement for heavy vehicle trailer tyres during the winter period in Sweden, and if so, suggest a new tread depth limit. The study was limited to ice conditions, and ice grip for a number of different trailer tyres with different tread depth was measured on smooth ice in VTI’s tyre test facility. Before conducting the test there was no clear hypothesis for how the ice grip would be affected by a lower tread depth. An increase of the grip, as well as a decrease, were both possible outcomes for a diminished tread depth. Four different tire models in a dimension common for heavy vehicle trailer tyres (385/55-R22.5) were chosen for the tests. Every model was tested in a new state, as well as with 5, 3, and 1.6 mm tread depth. It was decided to use naturally worn tyres which meant that in total 16 different tyres were used in the study. The difficult task of finding identical tyre models and dimensions with specified tread depth forced us to also include some tyres with the larger profile (285/65-R22.5). This is however not considered to affect the results of the test. All the tyres were winter tyres, and most of them were also marked with the 3PMSF symbol, which means that they have passed a standardized grip test on snow. Both brake and steer test were conducted. five different grip related attributes were investigated: peak friction at braking, friction at locked wheel braking, cornering stiffness, cornering peak friction, and cornering friction with large slip angle]]></description>
      <pubDate>Fri, 03 Apr 2020 15:48:24 GMT</pubDate>
      <guid>https://trid.trb.org/View/1696257</guid>
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    <item>
      <title>Pavement wear and its effect on surface texture and noise development on SMA 8 pavements in Norway</title>
      <link>https://trid.trb.org/View/1538172</link>
      <description><![CDATA[In the Nordic countries, pavement wear is among the main causes of early deterioration of asphalt pavements. The combination of harsh winter climates and mild summers leads to the formation of wheel ruts on the road surface due to both the use of studded tires and the heavy traffic loadings. The particular type of abrasion caused by the studded tires is known to affect significantly the surface texture of asphalt pavements, leading, among others, to possible alteration of acoustic characteristics of the road surface. This study aims therefore to investigate how it is possible to achieve satisfactory pavement life and noise properties of the road surfaces when studded tires are used. Based on laboratory tests and on site measurements, this project evaluated the development of the surface characteristics of three test sections, paved with a stone mastic asphalt with maximum aggregate size of 8 mm. Wear, texture and noise development were measured several years in a row in terms of rut depth, Prall and Nordic abrasion, texture spectra, MPD, shape factor G and noise levels respectively. Although several factors, such as workmanship and traffic distribution, are crucial for the long-term characteristics and the performance of the road pavement, this research shows in particular the relation between the development of wear and texture, due to the use of studded tires, and of the noise levels over time. Moreover, while the pavement wear slowly increases over time, due to the constant abrasion, the most relevant changes for texture and noise occur between the first and second year after paving and tend afterwards to stabilize.]]></description>
      <pubDate>Thu, 23 Aug 2018 14:38:22 GMT</pubDate>
      <guid>https://trid.trb.org/View/1538172</guid>
    </item>
    <item>
      <title>Crack identification by use of tire/road noise</title>
      <link>https://trid.trb.org/View/1538167</link>
      <description><![CDATA[The many functional aspects of the road are related to road surface characteristics, and it is difficult to evaluate road damage with single road surface property. Road surface conditions are mainly evaluated by the Maintenance Control Index (MCI) including main three distress factors using cracks, rut depth and roughness of the road surface in Japan. However, it is difficult to evaluate another localized distresses such as bumps, potholes, and faults of the road surfaces. In this research, focusing on tire / road noise, a new method to evaluate road surface damage was investigated. It is commonly recognized that tire/road noise is greatly influenced by the road surface smoothness (evenness) and the Public Works Research Institute (PWRI) frequently conducts monitoring the tire/road noise in terms of road environmental protection as well. In this case, it is critical to calibrate the measurement system of the road noise taking into account air temperature, vehicle speed and so on. In this research, we propose a new calibration method of the system correcting frequency characteristics based on the survey results of the community roads where road surface damages are anticipated. It is visually confirmed that the correlation between the tire/road noise and road surface texture is greatly high by the frequency analysis of the sound. The new method helps surveyor to identify the many distress conditions of localized defects, which have been difficult to find so far.]]></description>
      <pubDate>Thu, 23 Aug 2018 14:38:06 GMT</pubDate>
      <guid>https://trid.trb.org/View/1538167</guid>
    </item>
    <item>
      <title>Experimental validation of a brush-based approach to model runway friction measuring device</title>
      <link>https://trid.trb.org/View/1538154</link>
      <description><![CDATA[Water on runways may significantly reduce aircraft braking performances. That’s why pilots have to be informed about runway surface conditions, so they can calculate their required landing distance. Friction measuring devices are generally used to characterize runway surface conditions. These devices provide results that may not be representative of aircraft braking performances due to scale-effect (mass, speed, pressure…). A research work has therefore been launched by STAC and IFSTTAR in the framework of a PhD thesis to relate aircraft braking performances to ground friction measurements. A Brush-based model has been adapted to take into account the effect of water and applied to both one friction measuring device and aircrafts. This paper focuses on the validation of this model applied to the friction measuring device. Friction-slip curves have been measured by STAC laboratory on the IFSTTAR friction test tracks using the French reference runway friction device (IMAG, Instrument de Mesure Automatique de Glissance). The IMAG has been equipped with two tires (PIARC smooth tire and a grooved aircraft tire). A pool has been designed to maintain constant water depths ranging from 4 to 46 mm. Three increasing speeds have been tested until tires aquaplaning. A total of 35 friction-slip curves have been experimentally obtained and compared with predicted friction coefficients. Results show that the model is adapted to the IMAG configuration and measurements. The combined effect of water depth, vehicle speed and tire grooves is correctly described by the model, with an error in the range of +/- 0,06 friction unit. In this PhD thesis, a new approach is implemented to correlate IMAG friction measurements and aircraft braking performances on a physical basis. This physical basis makes this approach adaptable to any friction device, thus open the way to a physical harmonization of friction measurements.]]></description>
      <pubDate>Thu, 23 Aug 2018 14:37:23 GMT</pubDate>
      <guid>https://trid.trb.org/View/1538154</guid>
    </item>
    <item>
      <title>Winterreifen</title>
      <link>https://trid.trb.org/View/1508204</link>
      <description><![CDATA[Das Projekt geht der Frage nach, ob Winterreifen auf der Lenkachse von Lkw aus Sicht der Verkehrssicherheit sinnvoll sind, und welche Mindestprofiltiefe fuer Lkw-Winterreifen sinnvoll ist. Ziel ist es, den Einfluss von Lenkachsenwinterreifen im Vergleich zu Lenkachsensommerreifen auf das Brems- und Kurvenverhalten sowie den Einfluss der Profiltiefe von Antriebsachsensommerreifen auf das Bremsverhalten zu quantifizieren.  ABSTRACT IN ENGLISH: The project addresses the question as to whether winter tyres on the steering axle of trucks are expedient from the point of view of traffic safety, and which minimum tread depths are pertinent for truck winter tyres. The aim is to quantify the influence of steering axle winter tyres compared with steering axle summer tyres on the braking and cornering behaviour as well as the influence of tread depth of drive axle summer tyres on braking behaviour.  ]]></description>
      <pubDate>Tue, 22 May 2018 03:49:55 GMT</pubDate>
      <guid>https://trid.trb.org/View/1508204</guid>
    </item>
    <item>
      <title>Dynamic contact stiffness and air-flow related source mechanisms in the tyre/road contact</title>
      <link>https://trid.trb.org/View/1367668</link>
      <description><![CDATA[Two aspect of phenomena occurring in, and in the vicinity of the contact patch formed by a tyre rolling on a road are here investigated: 1. A detailed numerical time domain contact model is used to evaluate approximations of the tread response that are commonly embraced in tyre/road interaction models. 2. A statistical approach is applied in the search to quantify the contribution from air-flow related source mechanisms to the total tyre/road noise. Effects of inertia and material damping when the tread is locally deformed are often neglected in many tyre/road interaction models. How the dynamic features of the tread affect contact forces and contact stiffness is here assess by simulating the detailed contact between an elastic layer and a rough road surface. The dynamic case, with an elastic layer impulse response extending in time, is compared with the case where the corresponding quasi static response is used. The results indicate that the significant effect of material damping may approximately be included as an increased stiffness in a quasi static tread model if not very detailed processes are to be predicted. There are at least two main tyre/road noise generation mechanisms: tyre vibrations and air-flow related source mechanisms (commonly referred to as air-pumping). This study investigates the importance of air-flow related noise sources by employing the fact that their vehicle speed dependence differs from the noise produced directly by tyre vibrations. Results show that air-flow related sources are significant contributors to measured tyre/road noise. A comparison with results from calculated rolling noise indicates that tyre vibrations in/close to the contact may lead to noise with air-flow characteristics.]]></description>
      <pubDate>Tue, 01 Sep 2015 11:21:41 GMT</pubDate>
      <guid>https://trid.trb.org/View/1367668</guid>
    </item>
    <item>
      <title>A study of transient cornering property by use of an analytical tyre model</title>
      <link>https://trid.trb.org/View/1365403</link>
      <description><![CDATA[An analytical model for transient cornering properties is proposed for a small slip angle. The model, which is based upon the previous steady-cornering model, the Neo-FIALA model, approximates the entire deformation of a cornering tire by a combination of the shear deformation of tread rubber, the in-plane belt deflection and the out-of-plane sidewall torsion. It leads to a 2nd-order transfer function for side force. The steady-state gain and time constant of transfer function are expressed with some equivalent tyre-part stiffnesses, the concrete values of which can be determined from the measured load-dependence of steady cornering for a test tyre.]]></description>
      <pubDate>Thu, 13 Aug 2015 15:44:51 GMT</pubDate>
      <guid>https://trid.trb.org/View/1365403</guid>
    </item>
    <item>
      <title>Development of a grip and thermodynamics sensitive procedure for the determination of tyre/road interaction curves based on outdoor test sessions</title>
      <link>https://trid.trb.org/View/1365399</link>
      <description><![CDATA[Designers and technicians involved in vehicle dynamics face during their daily activities with the need of reliable data regarding tyres and their physical behaviour. The solution is often provided by bench characterizations, rarely able to test tyres in real working conditions as concerns road surface and the consequential thermal and frictional phenomena. The aim of the developed procedure is the determination of the tyre/road interaction curves basing on the data acquired during experimental sessions performed employing the whole vehicle as a sort of moving lab, taking into account effects commonly neglected.]]></description>
      <pubDate>Thu, 13 Aug 2015 15:44:42 GMT</pubDate>
      <guid>https://trid.trb.org/View/1365399</guid>
    </item>
    <item>
      <title>Analytical and finite-element study of the role of tread void ratio in terramechanics tyre behaviour</title>
      <link>https://trid.trb.org/View/1365397</link>
      <description><![CDATA[This paper presents an Analytical and Finite Element Study of a rigid plate and a rigid wheel with different tread void ratio patterns interacting with a deformable soil. FE models have been developed in Abaqus® and Drucker- Prager has been chosen as the failure criterion for the soil. The Drucker-Prager model has been replaced by a Mohr Coulomb failure model to be used in analytical modelling of the plate and wheel. A pressure-sinkage equation with invariant parameters is employed in the analytical models. Both longitudinal and lateral grooves are modelled and the improved traction performance of the latter is confirmed. Furthermore, the effect of tread void ratio is studied for both longitudinal and lateral treads.]]></description>
      <pubDate>Thu, 13 Aug 2015 15:44:36 GMT</pubDate>
      <guid>https://trid.trb.org/View/1365397</guid>
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