An experimentally based prediction model of road abrasion wear due to studded tyres is available in Sweden and has been found to work well. However, it has not been validated since 2007, and since then road surfaces and tyre design have developed, and the question has arisen regarding the model’s current validity. The abrasion wear model is used in the NORTRIP emission model (NOn-exhaust Road Traffic Induced Particle emission modelling), and the effect of a recalibrated abrasion wear model on the emission model is shown. In this paper, the abrasion wear model is compared to full-scale field measurements at several recently constructed roads in Sweden to investigate its validity, while also proposing changes to allow for continued use. It is concluded that the model overestimates the wear and an update is suggested. In addition, the impact on NORTRIP emission predictions is briefly investigated. There were also indications that NORTRIP is affected by the abrasion model overestimating the contribution of pavement wear to the particle emissions.

Stockholms stad bedriver sedan 2011 ett arbete med att, genom förbättrade och specifika gatudriftsåtgärder, minska uppvirvlingen av vägdamm för att minska partikelhalter i luften. Sedan starten har effekterna på såväl dammförråd som luftkvalitet följts upp av VTI och SLB-analys vid Miljöförvaltningen i Stockholm. Specifika åtgärder har omfattat främst dammbindning med kalciummagnesiumacetat (CMA) och städning med vakuumsug (Disa-Clean). Innevarande säsong har vakuumsugen dock inte använts. Luftkvalitetsmätningarna visar att miljökvalitetsnormen för PM10 klaras för femte året i Stockholm, men halterna är högre än föregående år. Vägdammsmängderna mätt som DL180 (vägdamm mindre än 180 μm) har generellt ökat vilket varit utvecklingen sedan säsongen 2014–2015. Folkungagatan, som fick en ny beläggning 2016, har fortsatt höga vägdammsmängder, men också lägre PM10-halter än före beläggningsbytet. Utvärderingen av möjligheterna att optimera dammbindningen visar att CMA ofta läggs ut trots att PM10-halterna inte skulle överskridits. Maj var särskilt torr och flera överskridanden kunde då ha förhindrats med CMA, men åtgärden avslutas sista april på grund av risk för halka. Högre precision med till exempel prognosbaserade åtgärder skulle sannolikt vara gynnsamt för optimering av insatserna.

The City of Stockholm has been working since 2011 on reducing, through improved and specific street operations, the suspension of road dust to the air. Since the start, the effects on both dust storage and air quality have been followed up by VTI and SLB-analys. Specific measures have included mainly dust binding with calcium magnesium acetate (CMA) and vacuum cleaning (Disa-Clean). However, the vacuum sweeper has not been used this season. The air quality measurements show that the environmental quality standard for PM10 is met for the fifth year in Stockholm, but the levels are higher than the previous year. Road dust loads measured as DL180 (road dust less than 180 μm) have generally increased, which has been the development since the 2014–2015 season. The Folkungagatan, which had a new pavement in 2016, still has high road dust volumes, but also lower PM10 levels than before the pavement change. The evaluation of the possibilities of optimizing the dust binding shows that CMA is often used even though the PM10 levels were not at risk to be exceeded. May was particularly dry and several PM10 exceedances could then have been prevented with CMA, but the measure ends in April due to risk of low friction. Higher precision with, for example, forecast-based measures would probably be beneficial for optimizing the efforts.

Objective: There is substantial evidence that exposure to airborne particulate matter (PM) from road traffic is associated with adverse health outcomes. Although it is often assumed to be caused by vehicle exhaust emissions such as soot, other components may also contribute to detrimental effects. The toxicity of fine PM (PM2.5; <2.5 µm mass median aerodynamic diameter) released from brake pads was compared to PM from other sources.

Materials and methods: PM2.5 of different types of brake pads (low-metallic, semi-metallic, NAO and ECE-NAO hybrid), tires and road pavement, poultry as well as the combustion of diesel fuel and wood (modern and old-fashioned stove technologies) were collected as suspensions in water. These were subsequently aerosolized for inhalation exposures. Female BALB/cOlaHsd mice were exposed for 1.5, 3, or 6 hours by nose-only inhalation up to 9 mg/m 3 .

Results: Neither cytotoxicity nor oxidative stress was observed after exposure to any of the re-aerosolized PM2.5 samples. Though, at similar PM mass concentrations the potency to induce inflammatory responses was strongly dependent on the emission source. Exposure to most examined PM2.5 sources provoked inflammation including those derived from the poultry farm, wear emissions of the NAO and ECE-NAO hybrid brake pads as well as diesel and wood combustion, as indicated by neutrophil chemoattractant, KC and MIP-2 and lung neutrophil influx.

Discussion and conclusions: Our study revealed considerable variability in the toxic potency of brake wear particles. Understanding of sources that are most harmful to health can provide valuable information for risk management strategies and could help decision-makers to develop more targeted air pollution regulation.

Vägbeläggningar av betong har potential att vara ett intressant alternativ till asfalt på flera sätt. Betong är normalt sett slitstark och saknar fossila komponenter, vilket är gynnsamt ur klimatsynpunkt och för brandsäkerhet i t.ex. tunnlar. Betong är dock dyrare att lägga, vilket medför att ur ett hållbarhetsperspektiv måste betongen vara både slitstarkare och kräva mindre underhåll jämfört med asfaltsbeläggningar. Syftet med föreliggande projekt har varit att ta fram ett betongrecept (Betong 2), med bättre egenskaper avseende slitage och partikelemissioner jämfört med en känd standardbetong (Betong 1) och en slitstark asfaltsbeläggning (ABS16) baserade på samma ballastmaterial. Inledande försök på pinne-skiva-maskin visade att nötning och partikelkoncentration för vägmaterialen av betong uppvisar en omvänd proportionalitet mot ballastens hårdhet, och en direkt proportionalitet mot glidsträckan.

I VTI:s provvägsmaskin jämfördes Betong 2 mot Betong 1 och mot en asfalt av typen ABS16. Provningen visade att slitaget var betydligt lägre för Betong 2 jämfört med referensasfalten (ABS16) och Betong 1. Genomgående genererar båda betongerna högre PM10-halter än asfalten. Ultrafina partiklar genereras i högre grad av asfalten. Orsaken till betongernas högre PM10-emission bedöms vara bidraget från cementpastan, vilket avspeglas i ett cirka tre gånger så högt kalciuminnehåll i PM10 från betongerna jämfört med PM10 från asfalten ABS16. Sammantaget visar både provningen i PVM och i detaljstudierna i pinne-skiva-maskin att Betong 2 har högre slitstyrka än både Betong 1 och asfalten ABS 16 och genererar generellt mindre PM10 än Betong 1.

Road paving of concrete has the potential to be an interesting alternative to asphalt in several ways. Concrete is normally durable and lacks fossil components, which is favorable from a climate point of view and for fire safety in e.g. tunnels. However, concrete is more expensive to lay, which means that from a sustainability perspective, the concrete must be both more durable and require less maintenance compared to asphalt coatings. The purpose of the present project has been to develop a concrete recipe (Concrete 2), with better properties regarding wear and particle emissions compared to a known standard concrete (Concrete 1) and a durable asphalt coating (SMA16) based on the same ballast material. Initial pin-on-disk machine tests showed that abrasion and particle concentration of concrete road materials exhibit a reversed proportionality to the hardness of the ballast, and a direct proportionality to the slip distance.

In VTI’s road simulator, Concrete 2 (the new recipe) was compared to Concrete 1 and against an asphalt of the type SMA16. The test showed that the wear was significantly lower for Concrete 2 compared to ABS16 and Concrete 1. Generally, both the concretes generate higher PM10 levels than the asphalt. Ultrafine particles are generated to a greater extent by the asphalt. The reason for the higher PM10 emission of the concrete is considered to be the contribution from the cement paste, which is reflected in an approximately three times higher calcium content in PM10 from the concrete compared to PM10 from the asphalt. Overall, both the test in road simulator and in the detailed studies in the pin-on-disc machine show that Concrete 2 has a higher wear resistance than both Concrete 1 and the asphalt SMA16 and generally generates less PM10 than Concrete 1.

Drift av gator och vägar påverkar, förutom framkomlighet och säkerhet, även miljöaspekter som luftkvalitet. Åtgärder som sandning och saltning påverkar halten av inandningsbara partiklar (PM10) i luften. Driftåtgärder som görs för att minska uppvirvlingen av partiklar på våren kan å andra sidan ha effekt på vinterdriften, genom att de saltlösningar som används också fungerar som halkbekämpningsmedel. Projektet har undersökt möjligheterna att optimera gatudriften ur dessa aspekter, med ett fokus på luftkvalitet. I olika aktiviteter inhämtades synpunkter och erfarenheter kring problembild och lösningar från bransch, väghållare och praktiker. En provtagare för vägdamm, WDS II, vidareutvecklades. Utvärderingar av olika spol- och städvarianters effekt på dammförrådet visade att en positiv effekt av metoderna kräver att det finns förhållandevis mycket damm på vägytan. Optimeringstester visade att god prognosstyrning av insatserna är viktigt för ett bra resultat. En kriteriebaserad analys visade att ingen optimering av dammbindningen skett under projektperioden. Sammantaget har projektets ursprungliga mål att kunna föreslå en optimerad gatudrift i en stadsdel i Stockholm inte nåtts, främst beroende av gällande driftkontrakt och av miljökvalitetsmålets (PM10) och framkomlighetens höga prioritet i staden. Däremot har Optidrift identifierat framgångsfaktorer och problem med gatudriften, resulterat i ökad kunskap om gatudriftens effekter på dammförråd och luftkvalitet samt tagit fram användbara utvärderingsmetoder och scenarioanalyser användbara i fortsatt arbete med att förbättra och optimera vinter- och barmarksdrift.

Operation of streets and roads, in addition to accessibility and safety, also affects environmental aspects such as air quality. Measures such as sanding and salting affect the content of inhalable particles (PM10) in the air. On the other hand, operational measures that are made to reduce the suspension of particles in the spring can have an effect on the winter operation, because the salt solutions used also act as de- and anti-icing agents. The project has investigated the possibilities of optimizing street operations from these aspects, with a focus on air quality. In various activities, views and experiences were gathered about problem images and solutions from industry, road managers and practitioners. A road dust sampler, WDS II, was developed. Evaluations of the effect of different coil and cleaning variants on the road dust load showed that a positive effect of the methods requires that there is relatively much dust on the road surface. Optimization tests showed that good forecasting of dust binding is important for a good result. A criteria-based analysis showed that no optimization of the dust binding occurred during the project period. Overall, the project's original goal of being able to propose an optimized street operation in a district in Stockholm has not been achieved, mainly due to current operating contracts and of the high priority of the environmental quality objective (PM10) and accessibility in the city. On the other hand, Optidrift has identified success factors and problems with the street operation, resulting in increased knowledge about the street operations' effects on dust load and air quality, and developed useful evaluation methods and scenario analyzes useful in continued work on improving and optimizing winter and barge operations.

Traffic related non-exhaust particulate sources and road dust are an increasingly important source for PM10 air pollution as exhaust sources are decreasing due to regulations. In the Nordic countries, the road dust problem is enhanced by use of studded tyres, causing increased road wear and winter road maintenance including gritting. Efforts to reduce road dust emissions requires knowledge on temporal and spatial road dust load dynamics. The city of Stockholm, Sweden, has therefore financed seasonal (October to May) road dust sampling to be able to optimize their winter and spring time street operation measures for reduced road dust emissions. This work describes the outcome of six seasons (2011/2012–2016/2017) of road dust sampling in five central streets using the VTI wet dust sampler (WDS).The results show that road dust load, expressed as DL180 (dust load smaller than 180 μm) has a seasonal variation with the highest loads (up to 200 g/m2) in late winter and early spring and a minimum (down to about 15 g/m2) in early autumn and late spring. The dust load varies between streets and is depending on pavement surface properties. On a smaller scale the dust load has a high variability across streets due to differences in rates of suspension from different parts of the road surface, with low amounts in wheel tracks and higher in-between and outside the tracks. Between 2 and 30% of the DL180 is smaller than 10 μm and could directly contribute to PM10 emissions. In general, higher road surface texture leads to higher dust loads, but the condition of the pavement (e.g. cracks, aggregate loss) might also have an effect. A new, wear resistant pavement accumulated markedly higher road dust amounts than a several years old pavement. This paper closes with a discussion on the complex relation between road dust load and PM10 concentrations and a discussion on the challenges and comparability of road dust sampling techniques and measures.

In northern countries, the climate, and consequently the use of studded tyres and winter traction sanding, causes accumulation of road dust over winter and spring, resulting in high PM10 concentrations during springtime dusting events. To quantify the dust at the road surface, a method—the wet dust sampler (WDS)—was developed allowing repeatable sampling also under wet and snowy conditions. The principle of operation is flushing high-pressurised water over a defined surface area and transferring the dust laden water into a container for further analyses. The WDS has been used for some time and is presented in detail to the international scientific community as reported by Jonsson et al. (2008) and Gustafsson et al. (2019), and in this paper, the latest version is presented together with an evaluation of its performance. To evaluate the WDS, the ejected water amount was measured, as well as water losses in different parts of the sampling system, together with indicative dust measurement using turbidity as a proxy for dust concentration. The results show that the WDS, when accounting for all losses, have a predictable and repeatable water performance, with no impact on performance based on the variety of asphalt surface types included in this study, given undamaged surfaces. The largest loss was found to be water retained on the surface, and the dust measurements imply that this might not have as large impact on the sampled dust as could be expected. A theoretical particle mass balance shows small particle losses, while field measurements show higher losses. Several tests are suggested to validate and improve on the mass balances. Finally, the WDS is found to perform well and is able to contribute to further knowledge regarding road dust implications for air pollution.

An experimentally based prediction model of rut development due to studded tyres is available in Sweden and which had been found to work well. However, since it has not been validated since 2007, during which traffic as well as road and tyre design have developed, the question has arisen regarding the model’s current validity. Also, since the prediction model is used in the NORTRIP (NOn-exhaust Road Traffic Induced Particle emission) emission model, a natural question is how a change in the wear model will affect the emission model. In this paper, two versions of the abrasion model are compared to measurements at several recently constructed roads in Sweden to investigate the validity, while also proposing changes to allow for continued use. In addition, the impact on NORTRIP is briefly investigated. The paper first describes the abrasion models and their calibration, as well as the test sections for calibration. Both versions of the model, as expected, overestimated the wear and an update was suggested. It was also found that NORTRIP is indicatively affected by overestimating the contribution of pavement wear to the emissions.

Stockholms stad bedriver sedan 2011 ett arbete med att, genom förbättrade och specifika gatudriftsåtgärder minska uppvirvlingen av vägdamm för att minska partikelhalter i luften. Sedan starten har effekterna på såväl dammförråd som luftkvalitet följts upp av VTI och SLB-analys vid Miljöförvaltningen i Stockholm.

Specifika åtgärder har omfattat främst dammbindning med kalciummagnesiumacetat (CMA) och städning med vakuumsug (Disa-Clean). Luftkvalitetsmätningarna visar att miljökvalitetsnormen för PM10 klaras för fjärde året i Stockholm vilket delvis bedöms beror på driftåtgärderna. Den extra dagtida dammbindningen kunde visas sänka dygnsmedelvärdet av PM10 med 6 %, medan den kvartersvisa behandlingen inte kunde visas ha någon tydlig effekt. Vägdammsmängderna mätt som DL180 (vägdamm mindre än 180 μm) tenderar att i genomsnitt ha ökat något jämfört med föregående säsong, särskilt i ytorna mellan hjulspåren. Omläggningen av Folkungagatan har resulterat i kraftigt ökade vägdammsmängder, men också lägre PM10-halter än föregående säsonger. Utvärderingen av möjligheterna att optimera dammbindningen visar att flera dagar med överskridanden på hösten missas, medan flera dagar i januari behandlas med CMA utan att behov egentligen föreligger. Högre precision med prognosbaserade åtgärder behövs för optimering av insatserna.

Since 2011, Stockholm City has been working to reduce the impact of road dust through improved and specific street operations to reduce particulate levels in the air. Since its inception, effects on dust load and air quality have been investigated by VTI and SLB-analys at the Environmental Management in Stockholm. Specific measures have mainly included dust binding with calcium magnesium acetate (CMA) and vacuum cleaning with a Disa-Clean sweeper. The air quality measurements show that the environmental quality standard for PM10 is maintained for the fourth year in a row in Stockholm, which is partly due to operational measures. Additional daytime dust binding could be shown to lower the daily average PM10 concentration by 6%, while blockwise CMA treatment could not be shown to have any clear effect. Road dust load, measured as DL180 (road dust less than 180 μm), tend to have increased slightly compared to the previous season, especially in between the wheel tracks. The repaving of Folkungagatan has resulted in heavily increased dust load levels, but also lower PM10 levels than previous seasons. Evaluation of the possibilities for optimizing dust binding shows that several days with exceedances in autumn are missed, while several days in January are treated with CMA without an actual need to reach the limit value. Higher precision with forecast-based measures is needed to further optimize the efforts.

The Treadwear Rating (TWR) provided on the sidewall of the tyre is a marking intended to inform the customer about the expected durability of the tyre. The current study explores whether there is a correlation between the TWR and tyres' tread mass loss. Furthermore, it explores the possible correlation between the TWR and tyre wear dust emitted in the form of PM10 and PM2.5. For that reason, two tyres of the same brand (B) but with different TWR and three tyres of different brands (C and D with the same TWR as one of the B tyres and A with a lower TWR) were tested at a constant speed of 70 km/h by means of the Swedish National Road and Transport Research Institute (VTI) road simulator. Tyres of the same TWR but of different brands showed different behaviour in terms of material loss, PM, and PN emissions under the selected testing conditions. This means that it is not feasible to categorize tyres of different brands in terms of their emissions based on their TWR. The test performed on the two tyres of the same brand but with different TWR showed instead a substantial (not statistically significant) difference in both total wear and PM10 emissions. The tyre with the higher TWR (B2) showed less wear and PM10 emissions compared to the B1 tyre having a lower TWR. Since only two tyres of the same brand and with different TWR were tested, this result cannot be generalized and more tests are necessary to confirm the relation within the same brand. In general, the tyre tread mass loss showed no obvious statistical relation to PM10, PM2.5 or PN concentration. In all cases approximately 50% (by mass) of emitted PM10 fall within the size range of fine particles, while PN size distribution is dominated by nanoparticles most often peaking at 20-30 nm.