The increasing proportion of paved surface due to urbanization means that the conditions for urban trees and vegetation to survive have deteriorated. Factors such as air pollution, poor drainage, and the lack of usable soil for root growth contribute to the short life expectancy of urban trees. To meet this challenge, several permeable and "structural" or "skeletal soils" have been developed as alternatives to the typical compacted soil required to bear the weight of vehicular traffic in urban areas. The main objective of this study is to evaluate the resistance to permanent deformation of permeable and skeletal soil pavement structures based on full scale accelerated pavement tests (APT) using a heavy vehicle simulator (HVS). Interlocking paving stones of various types were used as permeable surface layer for the test structures. The results demonstrated that the permeable test structures exhibited higher permanent deformation than the corresponding impervious structures. The skeletal soil with bituminous base layer, however, produced performance comparable to the impervious reference test structures.

Sammanfattningsvis definierar vi i denna guide ’smarta gator’ kort sagt som mångfunktionella, levande, långsamma, ekologiska och flexibla gator. Det övergripande målet med denna guide är följaktligen ”Smarta gator för en hållbar stadsutveckling”.

The global climate change is a reality and affecting society and transport systems. Climate change adaptation of transport systems will make the means of transportation more resilient and decrease the risk and magnitude of disruptions. Generally, climate change adaptations in road construction, operation and maintenance will need relatively large changes, but there is a shortage of the specific knowledge required as to what steps need to be taken, when and where, before measures can actually be implemented. Since climate change effects vary among Sweden's climatic zones, the impact of climate change on the road behavior and longevity is extremely difficult to predict. The need for winter maintenance in Sweden will generally decrease due to the warmer climate. Ploughing frequency will probably decrease as well, but preparedness should not be reduced too much since occasions with more extreme instances will increase. In order to succeed in making the road transport system resilient to climate change, we conclude that there is a need to develop more knowledge about the impact on the road infrastructure system as well as the operation and maintenance of the system including how to adapt through different types of variable and flexible climate adaptation measures and the effects of extreme weather events.

To study the correlation between the degradation of unbound base layer and mechanical properties (primarily Los Angeles test but also micro Deval test) a number of materials has been exposed by wheel load of VTI’s Heavy Vehicle Simulator (HVS). The first round was performed during the winter 2010–2011 and the second round during the following winter. In each round there were five materials tested. In the second round there were four new materials and one “old” as reference material. In this report results from round II will be presented, as well as some common results from both of the rounds, I and II. The results from round 1 are presented in VTI notat 4-2011. (Håkan Arvidsson: Comparison between the Los Angeles value and degradation from traffic load).The degradation has been defined as the difference in grain size distribution before and after HVS test. The degradation can be described in several ways. One way is as the difference in the area under the grain size distribution curve, another way is to sum the difference in percentage passing for all sieves or a few, e.g. the increase of fines by using results from the sieves 0.063–0.125 mm. The rutting has been measured by laser. The rutting is inversed proportional to the increase of fines. The increase of fines probably increases the stability in this quite coarse base layer grading. The materials with less increasing of fines have most of the hard minerals (quarts and plagioclase). The conclusion of these two tests on unbound base layer materials is that you partly can explain the degradation (change of grain size distribution) with mechanical properties (like Los Angeles and micro Deval). The correlations confirm this explanation and depend partly on an extreme material. Hellman et al (2013) show that degradation and crushing of the aggregates during compaction have a correlation with mechanical properties by studying microstructure and degree of crushing in microscope. Therefor the conclusion is that there is a degradation and crushing of aggregates in unbound base layer materials exposed by compaction and heavy traffic load.

Today in Sweden, biofuels and waste are the main fuels for the production of district heating and contributes to production of electricity. During combustion of biofuels and waste, it is also generates residues, so-called energy ashes. Large parts of the ashes have in original form or after sorting and processing good properties for construction purposes. Current use of energy ashes in Sweden are mainly as construction materials within the waste facilities as coverage of old waste dumps.. However, the need is decreasing as the coverage of many waste dump sites are about to be completed within the next 5–6 years. Therefore, there is a need for new applications for energy ashes. To deposit the ashes is a bad management of resources. Many ash producers have instead the ambition to use energy ashes for structures in society, such as in roads, parking lots and other fixed construction purposes. By using energy ashes for constructions and thus replacing virgin raw materials, the energy and waste system become more sustainable. This is an important factor for all the parts involved and shows concretely how circular economy can be created. Unless other disposal options evolve the cost will increase dramatically for ash management which stresses energy producers and ultimately also the end customer.

VTI arrangerade Transportforum 9–10 januari 2019 i Linköping Konsert & Kongress. En konferens, som är störst i sitt slag i Norden och som 2019 innehöll 90 sessioner med en stor variation mellan ämnen. Temat för 2019 års inledande session var elektrifiering – möjligheter och utmaningar att nå klimatmålen.

The European Direct-mat project provided a significant contribution to increasing recycling reclaimed road wastes. Part of the project was dedicated to the recycling of various reclaimed road materials in new hydraulically bound layers. This paper summarises the results of the project and the activities of the eight contributing European countries. Several examples from countries outside the project are also provided to give a comprehensive overview. The paper highlights the main trends of relevant practice worldwide (particularly in Europe) and draws conclusions for practitioners.

Experiments show that the deep drainage system is an effective method to control the groundwater table and, concerning road construction, it is recommended as a method when the road is located in earth cut below the ground surface in combination with high groundwater table. However, it is important to maintain the drainage system.

Along route 126 near Torpsbruk, the Swedish Transport Administration for many years had problems with bearing capacity, potholes and other deterioration. The problem obviously exists due to a combination of factors such as poor construction material, and high water content in the construction.

VTI experiments show that the deep drainage system is a very effective method to control the groundwater table. This was supported by the plugging trials. The water levels increased and decreased rapidly in connection with plugging and opening of the deep drainage system. Deep drainage is also a very effective method to control the water content in the road when the groundwater table is high in the road construction. Sealing of the road verge and embankment slope affected the dynamics of water content in the road. To investigate the infiltration of rain and road water some part of the road shoulder was sealed with a plastic tarpaulin.

The results can be used to evaluate if the use of sealed road shoulders might be an appropriate maintenance action. To evaluate the long-term effect of this action on the road construction and durability the measurements have to continue for a longer period of time.

Air quality in connection to streets with heavy traffic is a problem that affects the environment and people's health at many places. Photo catalytic properties of materials with nano sized TiO2 have been developed in recent years. Many research projects have focused on air cleaning properties of concrete and cement based materials. It has been shown that it is possible to decrease the amount of NOx gases and VOC (volatile organic compounds) in polluted air by using TiO2 in the products. The air is cleaned only by radiation of the photo catalytic active surfaces with UV-light (sunlight). This short literature survey aims to give information about how photo catalytic self cleaning works with nano sized TiO2 and how it can be used in road constructions. The report gives a general description about TiO2 and its field of use. It will also provide a review of some commonly used analyse methods to measure the self cleaning effect. The results of a few field experiments are also reported.

Mica is a common mineral in the Swedish bedrock and in some places the levels are high. Two important factors when it comes to road damages caused by high amounts of mica have been identified: moisture and frost damage. The Swedish Transport Administration requirements on the mica content needs to be reviewed, since they do not take into account a number of factors such as rock type, type of mica, used grain curve and climate factors. The purpose of this report is to compile the current state of knowledge on mica in unbound layers. Information about mica in asphalt is included because it contains information that may be relevant also for the unbound layers. The goal with this report is to identify knowledge gaps and define areas where greater understanding is needed about why and how mica minerals can be harmful in unbound layers in road construction. Damages associated with mica and other ballast-related properties can be difficult to understand because there are often multiple factors that interact and cause damage. Two important factors when it comes to road damages caused by high amounts of mica have been identified from literature and experience: 1. Moisture - high mica in combination with moisture produces higher risk of damages related to low bearing capacity and fast rutting development. 2. Frost damage - high mica decrease frost resistance and increase the risk of road damages. It can clearly be identified that more research is needed, including both laboratory experiments and monitoring of road sections, in order to find more relevant requirement demands on mica content in unbound aggregates for road construction.

This report is a literature review of the state of knowledge to understand the reasons for slipperiness on bicycle paths. The effect of texture on friction and slip risk and environmental impact is described. One of the main aims of the report is to present knowledge and needs around the friction and slip resistance of different types of surface courses under different conditions in cycle speeds up to 40 km/h. The slip risk is determined among others by the friction between the tire and the road surface. There are many factors that affect this friction, for example, the road surface's property, vehicle speed, tyre characteristics and the environment. This report focuses on the road surface's properties and meteorology (mainly temperature and humidity) and not on the bicycle or its component properties. The texture of the road surface is an important parameter when it comes to slip. The texture is divided into three wavelength ranges: micro, macro, and mega textures. Primarily, it is micro-texture and macro-texture that affect the friction of bicycles. In practice, the tire and the cycle path are rarely two clean surfaces that meets. Often, slip also occurs when the surface is dirty, water, snow and ice act as a friction-reducing layer between the wheels and the surface. Loose gravel also gives rise to slipping risk.

There are friction requirements for walking and cycling paths, although friction measurements are rarely carried out. Existing requirements in Sweden for surface course, including walking and cycling routes, are that the average friction number must not be less than 0.50 over a 20 meter long distance. Friction measurement can be done with PFT (Portable Friction Tester) as this hand-held instrument correlates well with the standard method Road (SAAB) Friction Tester which cannot be carried out on a bicycle path.

A number of roads have shortly after their construction had quality problems. The problems consisted of early rutting and cracking that result in increased maintenance costs. Despite heavy structures made of crushed rock, it has not been possible to avoid unfavourable quality development. According to the Swedish Transport Administration, these quality issues are particularly common if the subsoil consists of water-rich soils as silt and clay. The report aims to discuss the improvement and development of compaction of unbound materials in roads. In order to gather information and experience, a workshop was arranged with industry representatives with expertise in compaction. The basis for the contents in this report comes from the workshop and the discussions with the Swedish Transport Administration. The report also generally gives information about current Swedish compaction requirements and the most common methods to measure compaction quality.

In Sweden the rock qualities are based on mechanical analyses such as the Studded Tyre Test, Microdeval and Los Angeles Tests. One of the issues in this project is whether these tests are sufficient to determine the rock quality. The Heavy Vehicle Simulator (HVS) is a vehicle simulator at full scale in which the degradation of a road can be accelerated; the road can be exposed to large well defined traffic loads during a short time. In this project, the degradation and rutting of unbound base course have been studied. The results show that: (i) No clear relationship between rocks with high LA values or high MDE values with rutting development. (ii) The mineralogy of the rock material affects the rutting development. (iii) There is some correlation between the degree of the crushing and LA value. (iv) Some crushing provides increased stability and less rut depth development of trafficked base layers.

The confirmed results are in contrast to the current practice in road construction in Sweden, which suggest that materials with low LA values give lower rutting than materials with high LA values. The tests are performed under dry conditions which gives that the tests are not considering the impact of moisture on rutting and deterioration mechanism.

Mica is a group of minerals that is commonly found in Swedish bedrock and is a so-called sheet silicate. The two most common minerals are biotite and muscovite. Mica has a flaky grain shape and splits very easily in one direction, which means that during physical processing they divide into many thinner flaky grains called free mica. Unbound layers (unbond base course and sub-base) with a lot of mica grains generally have a reduced durability. The stability decreases, which can lead to increased rut depth and formation of cracks in the road construction. The fact that the mica breaks down into smaller grains if subject to the construction work processes and traffic load can worsen the problems and increase the amount of free mica grains, mainly in the fine fractions. 

Today, there is a lack of knowledge about which parts of the construction process that generate the largest proportions of free mica grains. The fact that mica easily splits or moves and accumulates due to crushing, transport and processing in the construction process makes it sometimes difficult to fulfill requirements and disputes can arise between supplier, contractor and customer. These issues are common in forensic investigations where high free amounts of mica have been found. 

The purpose of the project is to investigate and increase the understanding of which parts of the construction process that have the potential to increase free mica content in the fine fractions. The study covers various steps in the process, such as crushing in the quarry, material handling, transport, laying and compaction during road construction. Increase of free mica from construction traffic and traffic on a finished construction is outside this project. The aim of the study is to be able to improve the requirements for rock material and avoid problems that occur with high free amounts of mica.

Rubber has special properties compared to other materials. When used tires are recycled it results in products which largely retains the original technical characteristics of rubber. It is, for example soft, insulating, regains its original shape after a load and is durable. These properties can be utilized to produce products and structures with unique properties. For example; products that can withstand greater deformation without breaking, which dampen vibrations and noise, which has an insulating ability, purifying and stabilizing abilities and products. We can also add that it is persistent over time.

The construction industry has traditionally used mostly either unbound granular materials, (sand and rock material) or bound material (asphalt, concrete). Rubber material in the form of granules, for example, tire clip or the entire tyre offers unparalleled opportunities to perform new types of civil engineering structures with special advantages compared to traditional structures. Well known examples of how to create a new type of constructions based on the specific properties of rubber are artificial grass with rubber granules and appropriate soft protective coatings for playgrounds.

There are great potentials to develop constructions with unique properties where recycled material forms or is part of the construction, and will be wanted for its function and become profitable.

A basic problem, regardless of applications, is that this involves two different value chains and a natural link between these are missing. One value chain is construction and civil engineering and the other is the recycling of waste and residue products. These value chains have traditionally completely different focus in aim and purpose for businesses, so the desirable relationship with both “push and pull” is not naturally occurring. To create this link, some party must take responsibility for the need and the role that arise at the intersection of these value chains. Who takes this role is the leaping issue for further processing, manufacturing and managing where recycled tires wholly or partly constitute the raw material.

This report contains additional data from the study of moisture, drainage and groundwater along highway 126 near Torpsbruk, Sweden. The following are the main conclusions to be drawn from the experiments with sealed road verge and deep drainage system. Deep Drainage (with the Trammel system): • the installation of a deep drainage system can be recommended in places that have high ground water table and road cut in soil. • an effective method to control groundwater. • lowering the ground water table is very fast. • deep drainage can affect groundwater levels relatively far from the road area. • it reduces the moisture content of the road structure. • it needs to be maintained regularly. Sealed road verge: • no self-evident advantage of the sealed road verge in every case. • it stabilizes the moisture content – peaks of moisture and dry periods are leveled out. • it can prevent water from coming out of the road structure if water for any reason is coming in e.g. through cracks in the coating or penetrating groundwater. On the studied site are 13 groundwater level pipes (manual reading), 7 groundwater level pipes (automatic reading) and 4 pipes with moisture content sensors installed. Previous results are published in VTI Notat 13-2012.

VTI arrangerade Transportforum 13–14 januari 2021. En konferens som är störst i sitt slag i Norden och som 2021 hölls digitalt. Den innehöll ett 20-tal sessioner med en stor variation mellan olika ämnen. Temat för 2021 års inledande session var Coronakrisens påverkan på staden.

DIRECT-MAT (Dismantling and Recycling Techniques for Road Materials - Sharing knowledge and practices) is a European project in the Seventh Framework Programme. The project consists of 20 partners in 15 countries. The purpose of this project is, in a European perspective, share knowledge and experiences about recycling of road materials into new roads. The results will be presented in a web-based database where manuals, guides, national documents, references and literature studies are easily accessible. Case studies that exemplify the practical use of methods from the participating countries will also be available.

The project is divided into four groups that concentrate on recycling of different types of road materials. They are: - unbound road materials, - hydraulically-bound road materials, - asphalt-based materials, - other materials (e.g. ash, slag, rubber tires, contaminated sediment and vegetation from ditches).

This VTI report summarizes the Swedish experience of demolition, and recycling of road materials for use in new roads.

For many years, reconstruction of roads has been built on the sampling of existing materials in the road structure. There are various methods to accomplish this, which means more or less damages in the road. From experience, we know that it may differ in material layer build up depending on where the roadbed samples are taken. Sides of the road may differ; slope and road surface often have different structure which makes it critical were sampling was done laterally in the road structure.

Efforts in a reconstruction is to obtain as similar final product as possible, i.e. about the same service life along the entire route. If you get significantly different results along the route it may result in maintenance operations must be carried out earlier or later than expected. Previously Scheduled actions can be if they are extensive clearly increase the cost of a LCC perspective (Life Cycle Cost), while oversizing on the other hand can result in increased costs in the construction phase. For Road Administration planning, it is important that the right action is taken. It must be a balance between representativeness, road safety and cost when selecting sampling method.

During three bearing capacity projects on existing roads in northern Sweden it has been sampled from both the road verge and the roadway. Sampling has been done to receive layer structure build-up from each sampling method on each section.

The purpose of the study is to examine whether there is a difference between the two sampling methods, and if there is a risk that the wrong reconstruction action is selected based on the results. The report presents results from sampling along three roads, road 779Andersfors–Storbrännan, 897 Ålund– Jakobsfors and 726 Bygdsiljum–Burträsk. The results have been analysed whether there are systematic differences or similarities between the location of sampling and how these are related to the Transport Administration's rules for sampling, as described in TDOK2014: 0151 "Sampling of unbound materials."

The main mineralogical properties of rock materials used in road construction are described from a technical perspective in this VTI report. It is the quality of the rock material in combination with pavement design that determines future maintenance needs and technical lifetime of road construction. The report also presents a microscopic method for the determination of rock quality.

Road structures are composed of aggregates of different size fractions. Unbound aggregates are used for sub-base and base course layers. These layers should act as a foundation to be able to handle traffic loads and climate variations without deformation and break down. The properties of the unbound layers are largely determined by the rock quality (mineralogy, e.g.), grading curve and particle shape. Inferior materials can be used in less sensitive parts of the structure, while materials with high quality should be used in the more sensitive upper parts of the structure. In this way one can use the resources of rock quarries in the best way. The quality of the rock material and manufacturing determines future maintenance needs and technical lifetime of road construction.

The report contains a brief literature review in which the main mineralogical properties of the rock are described from a technical perspective.

The report presents a microscopic method for the determination of rock quality. It is designed to assess the technical characteristics of the rock for use as unbound material in road constructions. The method can be used in other contexts where technical characterizations of rock material are important. The method presents the quantitative assessment of mineralogy, grain boundaries, grain size, foliation and micro cracks. Appendixes contain examples of a completed analysis and pictures to facilitate the assessment and quantification of thin sections under microscope.

The report aims to identify new technologies for energy harvesting and the ability to use them in the road and the surrounding road area. The survey focuses on the materials and methods that may be used in the Swedish (cold) climate. The report can be useful for planning of new infrastructure when you want to make use of renewable energy and wants to reduce the environmental impact. Considering today’s technological conditions, the following techniques may be relevant: photovoltaics, geothermal energy, piezoelectric technology, wind energy or bioenergy. There are, however, many factors holding back the development of new innovative systems for energy production in roads and their environment. Some important factors are for example that maintenance costs will increase or that the maintenance of the road will become more difficult.

This report deals with a concept applying residual value estimations to applications in optimisation and procurement of road construction and maintenance. The purpose is to develop a framework and concept for tieing together technical and economical considerations in order to contribute to more optimised construction and maintenance of roads in a long-term perspective. This report is limited to investments in the pavement. Initially, the term residual value and its application in this context is investigated. Then, possibilities for prediction of pavement deterioration and performance are presented. These models are also linked to prediction of maintenance needs. Finally, a concept for cost predictions is developed with corresponding residual value applications, for example performance procurement, payment models, as well as more optimised pavement management from a life cycle perspective.

Stabilization of unbound layers of road structures is a promising technique from technical, economical and environmental point of view. The need of demonstration projects on road sections to show the relationship of laboratory measurements and field measurements are great in order to promote this stabilization technique.

The Swedish Government decided in 2017 to investigate different possibilities and challenges with implementing electrified roads in Sweden and since then, the Swedish Transport Administration has a program for investigations and research regarding electric road systems (ERS). The Research and Innovation Platform for Electrified Roads is part of this program and the present report is a compilation of the results derived regarding environmental impact of ERS from the work in work package two of this platform.

The general concept of ERS is to deliver energy for charging and propulsion of vehicles while driving.The environmental aspects that are covered in this report are mainly focusing on particles, noise and electromagnetic field emissions. The information is attained from literature reviews and discussions with project leaders of demonstration projects for electrified roads in Sweden. Comparisons were made with similar existing techniques or concepts. The overall results indicate that more research is needed on environmental impact of ERS, mainly regarding particles from the wear of conductive ERSas well as on emissions of electromagnetic fields. It is for instance important to consider emissions from electromagnetic fields as early on in the development phase as possible as well as looking intothe standards that regulates or need to regulate these technologies in order for them to work properly together with other electrical devices on or close to the roads. Screening of electromagnetic fields is an alternative, which could become a costly solution if considered later on in the process.

Water can impact the road in different ways both directly and indirectly. A well-drained structure is usually not affected by increased water volumes, but if water enters the road structure and remains there, it can, in combination with traffic loading, cause damage and deformation. Precipitation patterns will change with climate change. It may be drier in some places and wetter in others. Longer periods of heavy rainfall may become more common during some periods of the year, while other parts may be more affected by heavy rainfall. Road structures that already have problems with moisture and water penetration can be particularly vulnerable. It is becoming more important to have an overall view of which road sections that are particularly vulnerable, to be able to prioritize which parts of a road that are most in need of quick maintenance actions. 

This study highlights the possibility of using non-destructive ground penetrating radar (GPR) to detect variations in moisture along a road stretch. The purpose was to further investigate the possibilities of using GPR as a method for detecting moisture in the road, where the main purpose was to be able to perform the measurements by car at traffic speed. There are several different methods of GPR that can be used to detect moisture, but in this study, we chose to focus on the speed of the radar wave. 

However, the study showed that the analysis work is very time-consuming, which means that this method, as it is performed in this study, is not applicable as a method to be able to quickly measure longer distances with moisture-related problems. However, there is great potential for using GPR in combination with other road measurement methods such as road surface measurements and falling weight deflectometer to locate moisture-damaged road sections.

This paper presents the investigation of the deformation characteristics of two Open-Graded (OG) Unbound Granular Materials (UGMs) that are generally used in permeable pavement structures. Based on multistage Repeated-Load Triaxial (RLT) tests, the stiffness and resistance against Permanent Deformation (PD) of these materials were compared to their well graded (standard) counterparts. The OG UGMs showed similar stiffness characteristics as standard UGMs. On the other hand, the resistance against PD was slightly worse than the standard UGMs in a relatively dry state. However, the OG UGMs showed less sensitivity to moisture variation, yielding similar performance to that of standard materials at higher moisture content. The parameters of a stiffness model and a PD model were evaluated for these materials which may be used for prediction of rutting, estimating bearing capacity and for layer thickness design, using any suitable pavement design software.

Open-Graded (OG) Unbound Granular Materials (UGMs) are generally used in permeable pavement constructions. In this study, the Permanent Deformation (PD) characteristics of two OG UGMs were investigated by means of Multistage (MS) Repeated- Load Triaxial (RLT) tests. The influence of moisture on the PD behavior was also investigated. Compared to a few standard UGMs, these OG UMGs exhibited slightly lower resistance against PD in relatively dry state. On the other hand, these materials were less sensitive to moisture. Therefore, at higher moisture content, the OG UGMs and the standard UGMs showed identical PD behavior. Furthermore, the accumulation of PD was modelled using a simple model which may be used for prediction of rutting, estimating bearing capacity, and for layer thickness design, using a suitable pavement design software.

Most European countries are active in the field of recycling road materials, but knowledge and practice differ between countries. The European project DIsmantling and RECycling Techniques for road MATerials – Sharing knowledge and practices aims at sharing knowledge and practice in this field among the 15 participating countries, with the view of drafting European best-practice guidelines.

This paper reports on the first step towards this goal, which consists of summarising documented practices within these countries concerning demolition and recycling of road materials back into new unbound road layers. Common documented practice and major differences between European countries are highlighted and put in perspective, thanks to a broader international document review.