Transport Research International Documentation (TRID)

Generation and characterization of wear particles from ferrochrome containing asphalt

Fri, 07 Aug 2026 08:36:54 GMT

Ferrochrome slag is a byproduct of high carbon ferrochrome alloy production and has promising material properties for use as aggregate in asphalt wearing courses. However, concerns remain regarding chromium-containing particle emissions during asphalt pavement wear. This study investigates the wear behaviour, particle size distribution, and elemental composition of wear particles generated from asphalt mixtures containing ferrochrome slag. Eight SMA11 and SMA16 asphalt mixtures with different combinations of slag and granite (as aggregate and filler) were prepared and tested using Tröger and Prall abrasion methods. Airborne particles were measured with Aerodynamic Particle Sizer (APS) and Scanning Mobility Particle Sizer (SMPS), and elemental composition was analysed with X-ray fluorescence (XRF). Prall and Tröger results show that ferrochrome slag provides wear resistance comparable to the reference material (with granite from Skärlunda as aggregate and filler), despite mixtures not being optimized for slag-specific density or porosity. All mixtures generated particles across a broad size spectrum. Tröger abrasion resulted in coarser particles due to loss of the finest particles during dry collection, while Prall testing yielded finer fractions because particles were collected in water. Airborne PM10 concentrations were similar for all mixtures, and ultrafine particles (<100 nm) were emitted regardless of aggregate type. Elemental analysis of filters (total suspended fraction), collected wear particles from the Tröger apparatus (coarse fraction), and the fine fraction (PM2.5. revealed the presence of chromium in slag-containing materials. Chromium was also detected at low levels in the granite samples, likely due to abrasion of the steel needles in the Tröger apparatus. While chromium was clearly present in the generated wear particles, its oxidation state was not determined. Overall, the results indicate that ferrochrome slag can be used in asphalt wearing courses without increasing airborne particle emissions compared with conventional asphalt pavement. Further investigations on chromium speciation, leaching of fine fractions, and field-scale validation are recommended to ensure environmental and health safety. However, the results are based on laboratory experiments conducted under controlled conditions and although the methods are designed to simulate real studded tire wear, emissions and particle characteristics may differ under actual road conditions.

Marginal infrastructure costs and pricing in road and rail transport

Fri, 07 Aug 2026 08:35:44 GMT

This licentiate thesis examines marginal cost estimation and pricing in transport infrastructure, with empirical applications to Swedish roads and railways. The thesis consists of three papers addressing how infrastructure charges can be aligned with short-run marginal social costs. The first paper estimates marginal road renewal costs per heavy vehicle kilometre using panel data on approximately 1.3 million 100 meter road segments (1999-2022.. The second paper estimates short-run marginal road maintenance costs per heavy vehicle kilometre using administrative maintenance data at the Maintenance District Unit (MDU) level (2015-2024.. The third paper analyses optimal rail access charges in a vertically separated railway market, where marginal capacity costs reflect track congestion.

Tyre wear particles in the near-road environment of a Swedish highway : characterisation of concentrations and transport dynamics across snow, soil and through a stormwater system

Fri, 07 Aug 2026 08:34:39 GMT

Tyre wear particles (TWP) are increasingly recognised as a major source of microplastic pollution in urban environments, particularly in areas with high traffic intensity. Several laboratory studies suggest toxic effects from TWP and chemical compounds found in tyres, that can leach into aquatic environments. However, the occurrence of TWP in various environmental compartments remains poorly quantified, especially in the finer size fraction <20 µm. This thesis investigates the environmental concentrations, transport pathways, and morpho-chemical characteristics of TWP in the near-road environment of a Swedish highway. TWP were quantified across multiple environmental compartments-snow, soil, stormwater, sediments, and recipient waters-with special attention to the fine fraction (<20µm). The methodology employed for the analysis of the samples was a quantification of styrene-butadiene rubbers with pyrolysis-gas chromatography-mass spectrometry using a combination of marker compounds (benzene, α-methylstyrene, ethylstyrene, and butadiene trimer) followed by Monte Carlo simulations for calculation of TWP concentrations. The work in this thesis also includes quantification of other microplastic polymers in stormwater and detailed morphological and chemical characterisation of TWP in snow.

Digital twins for rail damage evolution in railway curves : field data, model calibration and reduced order models

Fri, 07 Aug 2026 08:34:25 GMT

Rails in railway tracks are subjected to complex rolling-sliding contact conditions that can cause surface and subsurface damage in the form of wear, plastic deformation, and Rolling Contact Fatigue (RCF). The prevailing operational conditions and maintenance practices of the rails strongly influence the evolution of this damage. If not managed properly, these mechanisms can degrade vehicle steering performance, increase noise and vibration levels, and in severe cases lead to rail failure or derailment. However, maintenance is costly and is difficult to plan correctly. Therefore, the ability to predict damage evolution is essential for effective maintenance planning and extending the rails' service life. This thesis presents a digital twin framework for the long-term prediction of rail damage evolution in railway curves under operational traffic conditions. The framework integrates field measurements of rail profiles with numerical simulations using models for the mechanical behavior of the rails. This enables continuous calibration and updating of model parameters based on observed rail behavior. The simulations are performed using models of dynamic vehicle-track interactions and accumulative rail damage computations considering plastic deformation, wear, and surface RCF. The calibration process adjusts parameters related to vehicle, track, contact model, and material properties, such as wear coefficients or yield limits, to ensure that the simulated degradation mimics the field-measured rail profile evolution. After calibration, the digital twins can predict railhead damage more accurately. To speed up numerical efficiency, a reduced order modeling framework has been developed for 3D rail geometry and plastic deformations. The framework adopts a convective coordinate system that follows a moving contact load and assumes a steady-state response.

Tyre wear particles : emissions and distribution in soil and stormwater systems in near road environments

Thu, 05 Feb 2026 08:33:49 GMT

Tyre wear particles (TWP) are a major source of microplastic pollution in road environments, yet their emissions, distribution, and environmental fate remain insufficiently characterised. This thesis presents a multi-scale investigation of TWP emissions in Sweden, their occurrence and distribution in two roadside ditches and one stormwater system, and the effectiveness of selected mitigation strategies. A detailed methodology was developed to estimate national TWP emissions using vehicle-specific emission factors and mileage data. Passenger cars were identified as the largest contributors (55%), followed by heavy-duty vehicles (31%), with rural roads accounting for the highest emissions. Field studies confirmed the occurrence of TWP in stormwater components such as gully pots, wells, and receiving waters. Fine particles 1.6-20 µm constituted a substantial portion of the total TWP load in both water and sediment samples. In roadside soils, TWP 97%), while more water-soluble compounds (e.g., HMMM, OHBT, MTBT, BTSA) exhibited variable leaching. The addition of biochar improved the retention of TWP, TDC and metals in fine, non-vegetative soils, and may contribute to climate mitigation by offsetting carbon emissions from construction materials such as concrete and steel. The thesis also evaluated mitigation strategies, including stormwater systems, road ditches, and bioretention filters. Bioretention filters with the addition of sorption materials demonstrated high removal efficiencies (97-100%) for TWP even under cold and high-flow conditions. The findings in this thesis contribute to improved understanding of TWP transport and retention and support the development of targeted measures to reduce microplastic pollution from road traffic.

Minskad spridning av mikroplastpartiklar från däckslitage : åtgärder på fordon, på väg samt i den vägnära miljön

Thu, 05 Feb 2026 08:33:33 GMT

Microplastic particles from tyre wear are estimated to be one of the largest sources of microplastic emissions in Sweden and globally. These particles can accumulate in the environment as they are toxic and difficult to degrade. They can be transported via air, water and snow, and spread in the ground. The spread can pose risks to ecosystems and human health, which justifies measures to reduce emissions and spread. The purpose of this report is to compile knowledge about measures aimed at reducing the spread of microplastic particles from tyre wear to the roadside environment. The focus is on techniques and strategies that are relevant to and can be implemented in a Swedish context. The method is based on a literature review, but above all on results from research projects that have been funded and carried out in collaboration with the Swedish Transport Administration.

Measurements of wear and resuspension from individual vehicles : WeaRS

Thu, 05 Feb 2026 08:33:29 GMT

It is well known that particles in air affect both climate and health. Due to more stringent regulations of exhaust emissions, more efficient engines and more hybrid and electric vehicles in the vehicle fleet, the exhaust-related particle emissions from road traffic have steadily decreased. Conversely, the emissions of wear particles from tires, brakes, and roadway as well as resuspension of road dust, today unregulated, is increasing in pace with a growing vehicle fleet. Quantitative data on non-exhaust emissions (NEE) is scarce. In this project a novel method was develop and tested for measuring and characterising the emissions of resuspension/wear particles from individual vehicles in real-world traffic. Measurements were conducted at the VTI road simulator, at a test track and in real traffic. The estimated emissions were characterised with respect to vehicle weight, speed, and road dust load and its characteristics, as well as compared to emissions resulting from the NORTRIP emission model.

Wheel and rail profile design : multi-objective optimisation of the wheel-rail interface using dynamic simulations to minimise wear and rolling contact fatigue

Thu, 05 Feb 2026 08:33:21 GMT

The interaction between wheels and rails is a key determinant of railway performance, safety, and maintenance costs. Degradations such as wear and rolling contact fatigue originate from the complex mechanical and dynamic processes at the wheel-rail interface. With increasing traffic demand, higher axle loads and greater operational speeds, these degradations intensify and lead to more frequent and costly maintenance. This thesis addresses these challenges by developing and applying multi-objective optimisation techniques for the design of wheel and rail profiles, with the overall aim of reducing damage rates and extending service life. A refined tangential contact modelling framework is introduced that incorporates a slip velocity dependent friction coefficient to improve the estimation of traction, wear and rolling contact fatigue. An index is developed to estimate the likelihood of curve squeal noise on specific track sections, thereby supporting noise mitigation strategies. The performance of two multi-objective optimisation algorithms, namely NSGA II and MOPSO, is analysed under identical conditions to provide insights into their suitability for profile optimisation. Practical implementation aspects, including grinding limitations, are explicitly considered to ensure that the optimised rail profiles are feasible for real-world application. The optimisation methodology is applied to both passenger and heavy haul contexts. For a broad-gauge heavy haul system, novel techniques are presented for optimising high and low rail profiles in curves as well as multiple profiles for tangent track. Furthermore, a systematic approach is proposed for the integrated optimisation of wheel and rail profiles on a dedicated heavy haul line, taking into account the requirements of the infrastructure owner.

Tyre wear indicator : framework for calculation of national emissions

Fri, 12 Sep 2025 10:19:41 GMT

Tyre wear is one of the largest sources of microplastic emissions both in Sweden and globally. Being able to estimate the size of this emission and how it changes in relation to changes in regulations, the vehicle fleet and tyre development is important for assessing the impact on ecosystems and health. The purpose of developing an indicator for tyre wear is to be able to update and monitor changes in national emissions and how different vehicle categories affect these in a manageable framework. The methodology for the indicator was originally developed within a government commission, where emission factors for tyre wear in passenger cars and light trucks were measured by weighing discarded tyres. For heavy traffic, there are no national measurements of emission factors, which is why current detailed data from the Netherlands has been rescaled for Swedish vehicles through weight and tyre number differences. Weight differences have also been used to scale emission factors between passenger cars, light lorries and motorcycles. The emission factors have then been combined with detailed data on annual milage and finally summarised. To make the indicator manageable, a calculation tool has been developed with instructions on what can be updated and at what intervals.

Measures to reduce the wear of road markings and thereby decrease the spread of microplastics

Fri, 12 Sep 2025 10:19:05 GMT

Trafikrelaterad mikroplast, det vill säga däckslitage, polymermodifierad bitumen och slitage från vägmarkeringar, är en av de största källorna till utsläpp av mikroplast i miljön. Vägmarkeringar som källa till mikroplast är ett relativt outforskat område och kunskapsluckorna är fortfarande stora kring slitagemängd, koncentrationer i olika miljöer och risker för människor och miljö. Det saknas dessutom kunskap på kommunal nivå kring vilken typ av vägmarkeringsmaterial som används, hur mycket material som köps in, och vad det kostar, liksom hur man säkerställer att markeringarna lagts ut på ett korrekt sätt, att tjockleken är korrekt, samt hur ofta uppföljning bör ske för att säkerställa att markeringarna fortfarande uppfyller sina funktionskrav. För att öka kunskapen hos kommunala och statliga väghållare initierades detta projekt. Målet har varit att ta fram en lättillgänglig och användbar handledning som bygger på fem olika ämnesområden: upphandling och regelverk; utformning och design; materialegenskaper; utläggning och underhåll; samt övriga åtgärder. Ett första utkast av handledningen presenterades på en workshop med ett femtiotal representanter från Trafikverket, entreprenörer, kommuner, Transportstyrelsen, branschen, samt deltagare från Statens vegvesen (Norge) och Vejdirektoratet (Danmark). Syftet med workshopen var att diskutera handledningens utformning och innehåll utifrån olika aktörers behov. En sammanfattning av diskussionerna presenteras i rapporten. Denna rapport är utformad som ett komplement till handledningen och erbjuder en fördjupning inom de fem ämnesområdena. Rapporten innehåller först en del med bakgrundsinformation med gällande standarder och regelverk, vanliga funktionsparametrar och begreppsdefinitioner, samt en beskrivning av olika typer av vägmarkeringar. Därefter presenteras detaljerad information kring fyra olika typer av vägmarkeringsmaterial: termoplastiska material, vattenbaserad färg, kallplast och vägmarkeringstejp. För- och nackdelar hos olika material, polymerinnehåll och materialens klimatpåverkan diskuteras. Därefter presenteras de vanligaste slitageprocesserna för olika typer av vägmarkeringar. Slutligen redovisas olika åtgärder, kopplade till de fem ämnesområdena i handledningen, som både på kort och lång sikt skulle kunna minska slitaget av vägmarkeringar och därmed reducera spridningen av mikroplast.

Åtgärder för att minska slitaget av vägmarkeringar och därmed reducera spridningen av mikroplast

Fri, 12 Sep 2025 10:18:38 GMT

Traffic-related microplastics from tire wear, polymer-modified bitumen, and road marking wear are among the largest sources of microplastic emissions. Road markings as a source of microplastics remain a relatively unexplored area, with significant knowledge gaps regarding wear rates, concentrations in different environments, and associated risks for humans and ecosystems. Furthermore, municipalities often lack information on what types of road marking materials they use, procurement volumes and costs, as well as methods for ensuring proper application, correct thickness, and necessary follow-up inspections to maintain functionality. To improve knowledge among state and municipal road authorities, this project developed a practical action plan covering five key areas: procurement and regulations; design and layout; material properties; application and maintenance; and general measures. A draft of the action plan was presented at a workshop with around 50 representatives from the Swedish Road Administration (Trafikverket), the Swedish Transport Agency (Transportstyrelsen), contractors, municipalities, the road marking industry and Nordic Road authorities (Statens vegvesen and Vejdirektoratet). The workshop helped refine the plan based on stakeholder needs, and a summary of discussions is included in this report. This report serves as a complement to the action plan, offering a deeper analysis of the five areas. It begins with extensive background information on relevant standards and regulations, key functional parameters, and definitions, followed by an overview of different types of road markings. It then provides a detailed examination of four main road marking materials: thermoplastics, water-based paint, cold plastic, and road marking tape, discussing their advantages, disadvantages, polymer content, and climate and environmental impact. The report also explores common wear mechanisms and presents various strategies-aligned with the plan's five focus areas-that could reduce road marking wear and, in turn, reduce microplastic contamination. Many of these strategies could also lead to cost savings by extending the lifespan of road markings and thereby reducing the material consumption.

High resolution air quality modelling of NO2, PM10 and PM2.5 for Sweden : a national study for 2023 based on dispersion modelling from regional down to street canyon level

Fri, 12 Sep 2025 10:18:31 GMT

In 2024, SMHI published modelled national high-resolution concentrations of NO2, PM10 and PM2.5 for the year 2019. The simulations were performed using a new methodology that enabled a combination of dispersion modelling on regional, urban and street scales without double counting of emissions. With a spatial resolution as high as 50x50 m2, these results provided the most detailed description of air quality over Sweden so far. Using the same methodology, we have now performed national simulations for the year 2023. Whereas the first project focused on developing a framework for model calculations, the aim of this project has been to further improve the model quality by improving emissions and modelling assumptions, as well as optimising calculation performance. Generally, the highest concentrations are seen in urban environments and along major roads. The traffic sector is one of the dominating source sectors.

Recherche zu Bremsstaubemissionen im Rahmen von EURO 7

Tue, 25 Feb 2025 08:48:13 GMT

Ziel ist es, eine Vielzahl von entwickelten beziehungsweise verfügbaren Bremssystemen hinsichtlich ihrer Eignung für den Einsatz in (teilweise) elektrifizierten Fahrzeugen insbesondere im Hinblick auf die zukünftig geplanten Grenzwerte der EURO 7 Norm zu analysieren. Beachtet werden sollen hier sowohl die Grundmaterialien der Bremskomponenten als auch deren Weiterverarbeitung inklusive Beschichtungen, zum Beispiel Kaltgas- oder Wolframm-Beschichtungen. Zusätzlich sollen Absaugsysteme und Kapselungen oder andere Emissionsminderungssysteme für Bremsabrieb analysiert und bewertet werden. Abschließend ist eine Empfehlung beziehungsweise ein Ranking für Bremssysteme von zukünftigen (teilweise) elektrifizierten Pkw zu formulieren, in welcher/welchem berücksichtigt wird, in welchem Maß die Bremsen vermindert durch den Rekuperationsanteil in den (teilweise) elektrifizierten Fahrzeugen beansprucht werden. ABSTRACT IN ENGLISH: The aim is to analyse a large number of developed or available brake systems in terms of their suitability for use in (partially) electrified vehicles, particularly with regard to the planned future limit values of the EURO 7 standard. Both the basic materials of the brake components and their further processing, including coatings (e.g. cold gas or tungsten coatings), are to be analysed. In addition, extraction systems and encapsulations or other emission reduction systems for brake abrasion should be analysed and evaluated. Finally, a recommendation or ranking for brake systems of future (partially) electrified passenger cars is to be formulated, taking into account the extent to which the brakes are less stressed by the recuperation share in the (partially) electrified vehicles.

Microplastic emissions from wear of road markings : overview and assessment for Swedish conditions

Fri, 17 Jan 2025 15:16:59 GMT

Traffic-derived microplastics, i.e., tyre wear particles, wear from polymer-modified bitumen, and road marking wear are assumed to be one of the largest sources of microplastic contamination. Road markings as a source of microplastic emissions are still a rather unexplored research area, and there arestill large knowledge gaps regarding annual wear, concentrations in different environments, and eventual risks for flora and fauna. This report has aimed to estimate the annual wear of road markings in Sweden and to investigate the knowledge on a municipal level related to road markings and wear. In addition, road markings from different traffic environments have been documented throughout the project, and the wear on these has been investigated. The project has also aimed to clarify which processes that contribute to the wear of road markings, as well as to map out which types of road markings that are subjected to specific types of wear. A survey was sent out to all municipalities in Sweden with questions about the type of road marking material, annual purchases, budget, wear rate, wear-prone traffic environments, and main causes of wear on road markings. In total, we received answers from 223 out of 290 municipalities.

Wear simulation study

Fri, 17 Jan 2025 15:16:04 GMT

The conditions at wheel and rail contact have a major impact on the economy of the whole railway system, as frequent reprofiling of wheels and rails due to wear and rolling contact fatigue are major cost drivers. This extensive study investigates the impact of different factors on wheel wear and risk of rolling contact fatigue (RCF). A large number of iterative wear simulations are compared to a reference case in terms of development of equivalent conicity, and risk of surface and subsurface RCF. The reference case is chosen to be representative of a typical vehicle operation in Sweden today.