Transport Research International Documentation (TRID)

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.

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.

Funktion och uppföljning av BGG (Blå-Grön-Grå) infrastruktur för klimatanpassning (Del 1. : dimensionering, bärighet och infiltration

Fri, 12 Sep 2025 10:19:50 GMT

Climate change is leading to increased precipitation, placing greater demands on stormwater management in urban areas. Traditional drainage systems are often insufficient, especially in densely built environments with impervious surfaces. Blue-Green-Grey (BGG) constructions offer a sustainable solution by combining structural load-bearing capacity, stormwater management, and support for vegetation. These systems feature a porous substructure of rock materials without fines that temporarily store water and are available in two types: with permeable surface layers or sealed surfaces with infiltration via inlets and drains. This project evaluated the load-bearing capacity and infiltration performance of BGG constructions at four locations in Sweden. Results show that BGG systems achieve comparable structural performance to conventional designs and maintain excellent infiltration capacity even after several years of use. The ERAPave (Elastic Response Analysis of PAVEments - Performance Prediction) design tool was used for planning, and the report includes guidelines for material selection and procurement. BGG systems show strong potential for climate adaptation in urban environments, particularly on low-traffic streets, pedestrian and bicycle paths, and public squares.

Stormwater bioretention systems : water quality treatment and long-term pollutant accumulation

Fri, 12 Sep 2025 10:19:43 GMT

Urban areas are affected by anthropogenic activities and produce pollutants that are transported to receiving waters bodies during precipitation. Greater awareness of pollutants has increased interest in treating stormwater. Organic micropollutants (OMPs, e.g., PAH, PCB, phthalates, and phenols) and metals (e.g. Cd, Cr, Cu, Ni, Pb, Zn) have been identified as potentially harmful to aquatic organisms and humans. Stormwater bioretention systems are popular and considered effective for stormwater treatment. However, there are significant knowledge gaps in bioretention systems' long-term function, performance of stormwater treatment in cold climates, impact of road salt on pollutant treatment, and issues related to operation and maintenance. Furthermore, pollutants have been found to accumulate in the filter material and are also a potential source of pollution. Thus, to understand the long-term function of bioretention systems, it is also important to understand occurrence and mobility of pollutants, and the processes of pollutant accumulation in bioretention systems, particularly in the filter material. To answer these questions, this thesis includes studies of stormwater sampling from 18 bioretention in Malmö, and three bioretention in Sundsvall (both in Sweden), along with a comprehensive field study involving sampling of 29 bioretention systems in the USA (filters that had been in operation for 7-16 years at the time of sampling). Filter material samples were collected from 31 bioretention facilities (37 filters in total), of which 28 were equipped with a forebay. A total of 277 samples were analysed for metals commonly found in stormwater (Cr, Cu, Ni, Pb, and Zn), and a five-step sequential extraction method was used to assess the metal mobility in the filter material. Additionally, 116 samples from 12 sites were analysed for 38 OMPs, including 16 PAHs, 7 PCBs, 13 phthalates, and two alkylphenols.

Microplastics and rubber in sediment collected over three years in road run-off treatment systems along highway E4 in Stockholm with particular focus on thermoplastic road markings

Fri, 12 Sep 2025 10:18:23 GMT

Paint in road markings contains microplastics (MP) which can be released by wear from traffic. High emissions of road MPs have been theoretically estimated in Sweden which has placed the road network as the worst MP polluter. Data from field measurements are scarce so if that gap could be filled it would shed light on previous assumptions. Two road run-off treatment systems along the E4 road through Stockholm city were studied for over three years. The primary aim was to cast light on selected mineral filters' capacity to remove dissolved pollutants, e.g. metals. The sediments collected in the two systems' reservoirs were later in focus for a study of MPs. Superficial water in the Lilla Essingen pond and the Gröndal sedimentation reservoir were removed by pumping until the bottom sediment was available for sampling. The pond and the reservoir are outdoor and indoor systems and the first-mentioned receives some stormwater from a housing area. Both systems receive road runoff from the Essinge route of the E4 road by gutters hanging under bridges. Ten sediment samples from each system were investigated for physical parameters and microplastic content. The Lilla Essingen pond stored less sediment than Gröndal due to its smaller catchment area, however, calculated per m2 runoff area it was the opposite 1.32 kg and 1.09 kg dry weight, respectively. This difference is caused by the pond receiving organic material from lawns within the catchment area. The microplastic analysis included 13 polymers and rubber of which only three connected to road marking paint (RMP).

Hydrologic processes of vegetated swales in controlling urban stormwater

Fri, 04 Apr 2025 15:14:29 GMT

Vegetated swales are elements of Green Stormwater Infrastructure (GSI) well suited for managing urban stormwater close to the source by reducing runoff volumes and peaks, keeping water in the urban landscape, and transporting excess runoff along the green paths. This dissertation explores swales hydrologic processes to advance the understanding of swale functioning under various conditions. Towards this end, the study comprised field experiments in two vegetated swales in Luleå (Northern Sweden) and a long-term monitoring of two paired catchments in Skellefteå (Northern Sweden). One of these catchments was served by a combined stormwater control measure (SCM) representing GSI, and the associated reference catchment was a nearby commercial development with traditional storm sewer drainage. The swales were tested in 24 controlled irrigation experiments mimicking runoff inflows. The combined SCM, consisting of a rocky slope, a vegetated slope and a vegetated collector swale arranged in series, was monitored to assess hydrologic parameters and responses based on natural rainfall inflows. Data were collected on rainfall events, inflow and outflow hydrographs, infiltration, and soil moisture.

Single-vehicle injury crashes on rural roads in Iceland: contribution of unforgiving roadsides to fatal and serious injuries of vehicle occupants

Thu, 06 Mar 2025 11:34:28 GMT

About 50% of the most severe crashes on rural roads in Iceland are run-off-road crashes. Many existing roads were designed before the concept of forgiving roadsides became prevailing in road design in Iceland. This research aimed to find the roadside elements that significantly increase the probability of high severity of single-vehicle injury crashes compared to low severity crashes on rural roads to prioritize safety improvements under limited budgets. In this research, 712 police records on single-vehicle injury crashes on rural state roads in Iceland in 2016–2018 were investigated. Crash data developed from police reports do not typically include information on roadside elements even though such information is often visible in photographs or written in words by police officers in their crash reports. This limits research on roadside elements and unforgiving roadsides. In this study, the original written police reports and crash photographs were reviewed. Based on this, additional data regarding the roadside elements were coded and added to the standard crash data. A binary logit model for the most severe injury in each crash was developed to statistically test the effect of roadside elements on the probability of fatal and serious injury versus low severity. The model results showed that two roadside elements, rocks and steep transverse slopes (e.g. where an access road enters a main road), hit by a vehicle in a run-off-road crash, more than doubled the probability of high severity. Road safety measures where roadside rocks are removed or steep transverse slopes are reduced, thereby making roadsides more smooth and forgiving, can be especially beneficial for safety because road users are unlikely to adapt their behavior to increased safety from such improvements. This is because such improvements are likely not easily noticed by road users; hence they reduce the probability of compensatory behavior such as increased driving speed, which could outweigh the safety benefits. The results revealed other contributing factors which more than double the probability of high severity of single-vehicle injury crashes on rural roads. Driver intoxication had the strongest effect, a problem which interestingly was limited to drivers living in Iceland. Not a single foreign tourist driver in this data was noted as being under the influence of alcohol or illegal drugs. To strengthen the analysis of the contribution of roadside elements to the severity of run-off-road crashes and to monitor the effects of improvements in the future, it is recommended that additional information on roadside elements be coded and added to the standard police record crash data.

Guide to road design part 5A: drainage: road surface, networks, basins and subsurface

Thu, 13 Feb 2025 09:02:40 GMT

The Guide to Road Design Part 5A: Drainage – Road Surface, Networks, Basins and Subsurface, provides road designers and other practitioners with guidance on the design of the collection and discharge of water from road surfaces, pit and pipe systems, basins and subsurface drains. This Guide needs to be used in conjunction with the other two Parts of the Guide to Road Design that relate to drainage design: Part 5: Drainage – General and Hydrology Considerations and Part 5B: Drainage – Open Channels, Culverts and Floodway Crossings. This Guide contains information on major/minor drainage systems, and the collection and discharge of road surface flows to support the operation and management of the road network. Guidance is provided on aquaplaning, and the design of drainage inlets and pipe networks receiving the flows. The principles of retention and detention basins and their design are also outlined.

Drainage of railway transportation infrastructure : status and environmental concerns

Fri, 17 Jan 2025 15:16:42 GMT

A literature study of water pollution potential of Railway Transportation Infrastructure (RTI) drainage has been undertaken, with emphasis on pollution sources and impact mitigation in Swedish conditions. RTI facilities can be divided into three categories: railway tracks (with associated structures), yards, and stations.

How to Drain Stormwater Without Ditches or Stormsewer and Catchbasins

Wed, 08 Jan 2025 13:52:32 GMT

Range Line Road is a two-lane road located in a residential area in the Town of Ajax, Ontario. Under existing conditions, it has a rural cross section on the west portion and an urbanized cross section on the east. Stormwater runoff drains toward Lake Ontario carried by ditches and culverts in the rural west portion, and by storm sewers in the urbanized east. With Carruthers Creek to the north and Lake Ontario to the south, a section of the road is within Toronto and Region Conservation Authority’s (TRCA) regulatory floodplain limit. Consultation with TRCA and local residents reveal that water from Lake Ontario can overtop Range Line Road during heavy rainfalls. Site investigations show there is minimal slope in the existing ditches and that groundwater levels are high. This is evident from culverts heaving up and cracking in the existing pavement along Range Line Road and adjacent driveways. After consultation with the public the Town reaffirmed their decision to rehabilitate the road pavement and to extend the existing sidewalk on Range Line Road through the rural west section as part of their ongoing effort to improve road safety and active transportation network connectivity. The sidewalk extension will fill in the existing ditches to minimize grading impacts onto adjacent residential properties. Normally, storm flows drained by gravity sewers would be proposed but this will not work here because of the limited ground cover available due to the minimal difference in elevation between the road and the lake. Without a viable drainage system to drain water away from the road, the new pavement will not reach its expected service life, and the new culverts will continue to heave up against the new pavement. Through extensive collaboration with the Town and a well-known manufacturer, the project team delivered a design that achieved the Town’s objective in extending the sidewalk while utilizing a unique slot-drain system along the new curb and gutter in lieu of the conventional stormsewer and catchbasin system to facilitate drainage and thus improve the new pavement’s chances of reaching its expected service life. While the same product has been used before on one of MTO’s Highway 401 projects, the Town of Ajax is one of the first municipalities in Ontario to use it on their roads. Main design challenges include demonstrating the product’s durability, constructability, and maintenance effort to Town’s Road Operations. All construction work was completed in December 2023.

Limited Roadside Visibility: Analysis & Effects

Wed, 08 Jan 2025 13:52:31 GMT

Run-off-road collisions are going unnoticed, obscured from the view of passersby due to factors such as steep roadside slopes, bodies of water, and dense foliage. Consequently, road-users are disappearing, perishing, and first responders are being misplaced or are unable to act. Current literature does not address the hazard of concealability of ROR collisions within limited roadside visibility areas, and the extent of its impact, by nature, cannot be fully know A case study of a North Saanich couple who were reported missing in August of 2019 is explored. Tragically, the couple was found deceased forty feet from the highway down a steep embankment and just out of sight from their families and the police officers who drove past them. Through analyzing the design elements and topography of a roadside’s cross section, this study demonstrates which run-off-road collisions may become hidden, and where. A map of such locations can then be compiled to assist authorities, Search & Rescue operations, and families in locating victims of this hazard, as well as to quantify the scope of the associated risk. This research finds that, due to many factors, run-off-road collisions are easily concealable, and the number of these locations is significant. Not only are lives being lost unnecessarily, but the cost to communities is substantial. When locations with limited roadside visibility are charted, search parties are provided a strategic vantage point for rescue and recovery, cost estimates of future roadside safety treatments capable of collision detection are more accurately derived, and first responders are enabled to act in a more efficient manner. This approach can help mitigate the severity of roadside collisions, save lives, protect the environment, and significantly reduce the cost of ROR collisions to communities.

Infiltrationssystem vid vägkanter för behandling av vägavrinning i Norden

Thu, 10 Oct 2024 14:38:30 GMT

Roads may cause harm to the environment in many ways. Increased traffic loads and construction of new roads, as well as maintenance, may cause short- and long-term effects on the aquatic environment due to the discharge of contaminated runoff. Pollution reduction is thus a key challenge for the national road administrations (NRAs). Different mitigating measures, such as infiltration systems, are built to treat storm water runoff. Proper maintenance is also critical. The CEDR project Water Quality Call 2016, and the NordFoU project Reducing highway runoff pollutions (REHIREUP) were recently finished. These projects produced new knowledge to be implemented, but also identified knowledge gaps that needs to be further explored. As a follow up of these projects, and thus a long cooperation between Norwegian Public Roads Administration (NPRA) and the Swedish Transport Administration (STA), we suggest a continuous joint effort on topics within highway runoff pollution and associated flows under the umbrella of NordFoU. The main purpose of this NordFoU-project is to increase the knowledge and produce guidance on infiltration solutions used for pollution control, and to exchange information on water pollution issues between project partners. Joint effort on mutual challenges is economically efficient, environmentally motivated and will give more value for money. A major focus will be on producing result that can be directly implemented in e.g. guidelines and handbooks for building and managing roads. The project will use literature review combined with sampling and measurement campaigns to gather new knowledge about the topic.

Utformning och implementering av naturbaserade dagvattenlösningar för hållbara städer

Thu, 10 Oct 2024 14:38:21 GMT

GreenStorm targets nature-based solutions designed to manage stormwater (NBSsw) as a means of urban transition, with a specific focus on climate adaptation, resilience of urban vegetation, but also enhanced social benefits. The hydrologic and thermal performance of NBSsw during present and future climate extremes (high intensity rainfall, drought, heat waves, frost/thaw) will be assessed for a range of NBSsw structures and a wide span of European climates, by coupled monitoring / modelling. Improved NBSsw structures, and pathways for their acceptable implementation in urban areas will be developed based on co-creation workshops with all relevant stakeholders (professionals and citizens). A real case study in Copenhagen will serve to demonstrate NBSsw implementation in a community engaged approach and, based on a cross analysis with data and feedback from Paris, Athens, Genoa and Östersund, will allow to identify drivers for NBSsw upscaling. Based on these results, potential for widespread implementation of NBSsw at large urban catchment scale will be analysed in the 5 partner countries (France, Denmark, Sweden, Greece, Italy) and the hydrologic/hydraulic and thermal benefits will be modelled.

Factors associated with single-vehicle crash occurrences on Indonesian toll roads

Tue, 17 Sep 2024 14:48:23 GMT

Crashes on toll roads can be extremely hazardous, resulting in fatalities and serious injuries due to high speeds. Although multi-vehicle crashes are more commonly observed on Indonesian toll roads, single-vehicle (run-off-road) crashes should not be disregarded, as they also pose a significant risk of fatality. To identify the factors contributing to the occurrence of single-vehicle crashes on Indonesian toll roads, this study developed a crash prediction model that incorporates both geometric and traffic characteristics of toll roads, using a Negative Binomial regression model. The results indicate that higher average daily traffic, segments without roadside crash barrier, and segments with median concrete barrier are associated with a higher frequency of single-vehicle crashes. Conversely, the presence of a nearby ramp, bridge pillars, and segments with rigid pavement are associated with a lower frequency of single-vehicle crashes.