Table of contents

These proceedings contain full reports submitted in an open call to the 30^th International Baltic Road Conference held virtually on August 23 and 24, 2021.

The conditions for including the reports in these proceedings were the following:

1. Full reports were submitted before the formal deadline of March 15, 2021,

2. Authors of reports have expressed their consent to include their reports in these proceedings.

All conference organisers/editors are required to declare details about their peer review. Therefore, please provide the following information:

• Type of peer review: Single-blind/Double-blind/Triple-blind/Open/Other (please describe)

Each paper was blind peer-reviewed by two reviewers. Members of the Conference scientific committee served as reviewers.

• Conference submission management system:

EasyChair platform (easychair.org) was used for the management of the Conference papers.

• Number of submissions received:

Initially the Conference organiser received 86 abstracts of scientific papers.

• Number of submissions sent for review:

82 submitted reports were sent for review.

• Number of submissions accepted:

50 papers were accepted.

• Acceptance Rate (Number of Submissions Accepted/Number of Submissions Received X 100):

(48/86) x 100 = 56 %

• Average number of reviews per paper:

Two.

• Total number of reviewers involved:

Thirteen reviewers from 3 countries:

1. Alfredas Laurinavičius, Dr.sc.ing., Vilnius Gedemina Technical University, Lithuania

2. Andrus Aavik, Dr.sc.ing., Tallinn University of Technology, Estonia

3. Artu Ellmann, Dr.sc.ing., Tallinn University of Technology, Estonia

4. Atis Zarins, Dr.sc.ing., Riga Technical University, Latvia

5. Audrius Vaitkus, Dr.sc.ing., Vilnius Gedemino Technical University, Lithuania

6. Dago Antov, Dr.sc.ing., Tallinn University of Technology, Estonia

7. Daiva Žilionienė, Dr.sc.ing., Vilnius Gedemino Technical University, Lithuania

8. Donatas Čygas, Dr.sc.ing., Vilnius Gedemino Technical University, Lithuania

9. Juris Smirnovs, Dr.sc.ing., Riga Technical University, Latvia

10. Viktoras Vorobjovas, Dr.sc.ing., Vilnius Gedemino Technical University, Lithuania

11. Viktors Haritonovs, Dr.sc.ing., Riga Technical University, Latvia

12. Ainars Paeglitis, Dr.sc.ing. Riga Technical University, Latvia

13. Janis Barbars, M Eng., "Latvian State Roads", Latvia

• Any additional info on review process:

Summaries/abstracts of the submitted papers were also reviewed in preliminary evaluation.

During evaluation the following factors were considered:

1. Whether thehe author is familiar with the existing state of research,

2. Whether the topic is relevant to the scope of 30IBRC and corresponds to one of the seven main themes of the Conference,

3. Whether the report his is a new and original contribution,

4. Whether the title is appropriate,

5. Whether thehe abstract and keywords are adequate,

6. Whether the presentation of material is logical and technically correct,

7. Whether the interpretations and conclusions are sound and justified by the results,

8. Whether the writing style/English is clear and understandable,

9. Whether the paper is of the right length,

10. And finally, whether the references are adequate.

After the evaluaton the following recommendations were expressed towards each report :

- Acceptable without any changes

- Acceptable with modifications

- Unacceptable

• Contact person for queries:

Martins Dambergs martins.dambergs@lvceli.lv

Please submit this form along with the rest of your files on the submission date written in your publishing agreement.

The information you provide will be published as part of your proceedings.

The expectations placed on the existing European transport infrastructure are increasing due to the growing mobility needs of the population on the one hand and the rising volume of freight traffic on the other. The aim of the European ITS Platform is to increase the efficiency of the TEN-T core network through a better use of the existing infrastructure by implementing Intelligent Transport Systems (ITS). It fosters interoperability and the development of uniform technical standards by monitoring and disseminating the results delivered by the five CEF ITS Road Corridor Projects.

One major outcome is the drafting of the "Reference Handbook for harmonized ITS Core Service Deployment in Europe". This digital freely available handbook comprises a series of guidance and advice for use by road authorities and operators to support them in the development of their strategic approach, design development, deployment, installation and operation of ITS and remain compliant with European legislation. Its key features include: Deployment Guidance for 14 different ITS Services, including DATEX reference profiles, Guidance on the provision and use of traffic information provided under the European Directive (2010/40/EU), C-ITS developments, Knowledge gained from the collection of 100 Best Practices etc.

Road infrastructure asset management is rapidly transforming into a digital environment where data accessibility, effective integration and collaboration and accessibility from different sources and assets are key. However, current asset management processes are not yet fully integrated or linked, and there are incompatibilities between various systems and platforms that limit the ability to integrate asset management with BIM. The CoDEC project has sought to understand the current status of information management for assets, including inventory, condition and new data sources such as sensors and scanning systems, to identify the challenges and needs for linking and integrating different data sets to support effective asset management. As a result, CoDEC has developed a data dictionary framework to help link/integrate static and dynamic data for the "key" infrastructure assets (road pavements, bridges, tunnels). This will enable BIM and Asset Management Systems (AMS) to exchange data and help optimise and integrate data management across systems and throughout the different asset lifecycle phases, from build to operation. This work will be followed up with three pilot projects to demonstrate the feasibility of integrating asset data from various sources through linked data/semantic web technology to build the connection between AMS and BIM platforms.

Road asset management (RAM) is a crucial aspect in the development of transportation network. RAM framework should be understood as a rational approach to business model for road authority, which dictates its business processes in a systematic and objective-based manner to ensure that strategic goals of an agency are reached. In a case of road network, such objectives are typically related to travel safety, time and comfort that should be maintained throughout the life cycle of the road assets at optimal costs. As such RAM enables road agencies to meet expectations of its customers to provide safe and reliable road network in effective and efficient way. Nowadays it becomes even more important to adopt performance-based and data-driven approach for road agencies considering current trends in transportation like connected, cooperative and automated mobility.

There are many aspects of RAM including legal, economic, technical and managing aspects. These aspects are inter-connected and nowadays agencies build and incorporate RAM system to establish a common denominator for all agency activities at all organizational levels. This paper discusses selected aspects of RAM in Poland. Since national road network in Poland is relatively new, it is particularly important to go over well designed and detailed implementation process. It should comprise numerous items including self-assessment and gap analysis, change strategy and transportation asset management plan (TAMP). This paper present update on these activities as well as presents future plans in order to establish modern, effective and sustainable RAM framework in Poland.

Latvian State Road Development Strategy for 2020 – 2040 was approved in the year 2020. It is a vision that includes long-term perspectives, strategic goals, tasks and priorities for road network development, and it is created for more efficient planning of state road network development, as well as, attracting additional funding for state owned roads.

The aim of the Strategy 2040 is to create an efficient road network ensuring that the bypass of the Riga City is accessible within two hours from every national and regional development centre in Latvia. Development centres would be accessible within 45 minutes from every Latvian urban settlement along state regional and local roads.

The strategic task is to create sections of express roads in the total length of 1000 kilometres thus improving traffic safety and reducing the emissions of greenhouse gases.

When creating the Strategy 2040 both the changes in traffic and road use and the changes in the location of population were studied. The Strategy foresees that high-speed express road sections would connect the Riga City with the biggest cities. The proposed plan of road network development is created with the aim to cover as large a population as possible.

Special attention is paid to the Riga City, as it serves as the central hub for Latvian and Baltic transportation. After the implementation of the Strategy 2040, the Riga City would be reached within 30 minutes from the nearest development centres.

Kekava Bypass public-private partnership (PPP) project is the first highway infrastructure PPP project in the Baltic States to be implemented according to Design-Build-Finance-Maintain (DBFM) model. Its objective is to solve the "bottleneck" of the TEN-T network road section entering Riga City with only one lane in each direction. The duration of the project is 23 years, including 3 years for design and construction of the infrastructure and 20 years for its maintenance. Kekava Bypass consists of the main road 17.22 km, auxiliary roads 20.66 km, 2 tunnels, 5 two-level road junctions, 1 bridge (all in all more than 100 lane km), 2 pedestrian bridges/tunnels etc.

The Latvian government required that the assets of the Kekava Bypass project are classified off government balance sheet during the whole duration of the PPP contract. Thus, the Kekava Bypass PPP tender documentation was elaborated strictly observing this off-balance sheet treatment frame. Eurostat assessed the project documentation and issued its opinion that the project corresponds to the off-balance sheet criteria.

Latvian State Roads on behalf of the Ministry of Transportation launched Kekava Bypass tender in December 2018. The tender was implemented in four sequent phases, namely, the qualification phase, the submission of initial offers, negotiations with the selected bidders about the initial offers, the submission of the best and final offers. On August 13, 2020, Latvian State Roads announced the winner and the financial due diligence phase to be performed by financial institutions started.

In 2021 a new territorial reform will be carried out in Latvia, and the number of existing 110 local governments will be reduced to 42 regions (previous territorial reform in 2009 resulted in the decrease of the number of local governments from 522 parishes down to 110 local governments).

Each territorial reform has always regarded the importance of the network of state owned roads in ensuring successful operation of local governments, management of their territories and provision of municipal services to local inhabitants.

After the previous territorial reform carried out in 2009 there were 104 centres of local governments that were not connected with paved roads. At present only 59 such centres without paved road connections have remained, and improvements on roads serving these local governments is continued in the scope of annual improvement programmes financed from the state budget.

The Ministry of Environment and Regional Development within the scope of the new territorial reform in 2021 is preparing a new Investment Programme for Road Development in the Context of Territorial Reform. Respective road sections are identified by the administrations of planning regions in co-operation with local governments, the programme itself is compiled by the Ministry of Environment and Regional Development, but State Limited Liability Company "Latvian State Roads" is providing consulting on the choice of most efficient rehabilitation methods, preparation of technical documentation and potential construction costs.

The total length of Via Baltica corridor, which consists of five roads (A5 Kaunas–Marijampolė–Suwałki, A1 Vilnius–Kaunas–Klaipėda; A8 Panevėžys–Aristava–Sitkūnai, A17 Panevėžys bypass and A10 Panevėžys–Pasvalys–Riga) makes up 268 km on the Lithuanian territory. In 2019 the highest traffic volumes on this corridor were 55,942 veh/day. It is the highest-volume heavy vehicle road carrying the greatest loads. Via Baltica is a transit road; therefore, it shall comply to the requirements set to high quality roads. In 2020-2030 it is planned to implement 9 projects, the total value of which is ca 704 million EUR (194.18 km to be reconstructed). Until 2018 having implemented 156 million EUR projects, Via Baltica road A5 Kaunas–Marijampolė–Suwałki 17.24–56.83 km section (from Kaunas to Marijampole) was reconstructed into a motorway until the end of 2018. Currently, preparations are made for Via Baltica reconstruction from Marijampole to the Lithuanian-Polish border (A5 road from 56.83 km to 97.06 km). Strategic Environmental Assessment has already been completed and a special territorial planning document has been approved by the Lithuanian Government. According to this document, the road section shall be widened up to four traffic lanes by constructing two safe grade-separated intersections (viaducts) and roundabouts, connecting roads, a new heavy vehicle parking lot, by widening the existing bridges, by building new bridges and by implementing various environmental protection measures. At present design works of the above-mentioned 40.23 km-long-road section are underway. The works are due to be completed by the end of 2025.

The current road user charge in Lithuania is based on a temporary system and is not connected to the actually covered mileage. The time-based charge is not considered to be socially fair; therefore, the principles 'user pays' and 'polluter pays' shall be employed. The charge to be introduced will take into account the interests of local road infrastructure users who are currently paying unreasonably high charge for a short distance covered.

If the current system is retained and e-tolling system is not established, heavy vehicle drivers would continue paying aroad user charge by purchasing e-vignette. It would mean that road user charges paid by vehicle owners/holders would not cover the damages directly made by the user and the current road charging system would not guarantee sufficient financing for the maintenance and development of the road infrastructure.

Legal decisions on electronic road charging system have not been taken yet; however, the project implementation preparation is underway. The latest Parliamentary approvals were received in September 2020, and it is believed that all necessary legal acts will be amended by the end of 2020.

The road charging technology has not been selected yet. However, the conducted project's implementation analysis, the assessment of necessary investments and road charging system maintenance costs revealed that a GPS-based technology would be the most economical one.

It is planned to implement the electronic road charging system by the beginning of 2023. Upon the project's implementation, additional financing to ensure high quality and safe main roads should be allocated.

Road pavement is expected to withstand enormous traffic loads for long time but sooner or later the deterioration reaches levels when its optimal to apply treatment. While easy to measure roughness or rutting in normal traffic speed, defects are in most countries still collected by means of time-consuming visual inspection in low traffic speeds or expensive and difficult- to-use equipment. Also, most visual inspection systems only operate with aggregated inspection data. That makes data-collection expensive and defects-based decision-making inefficient. In Estonia, defects inventory system utilizes high quality panoramic and orthogonal images to enable data collection in traffic speeds and detailed mapping of pavement defects in 10 classes. Defects mapped in full detail means, that location, shape and size of each defect is known and classified data can be effectively used twice in pavement maintenance planning: for section selection planning in road network level when aggregated and for work method selection in design process when analyzed in detail. Combined with measured lidar-based point-cloud data, detailed 3d-basemap saves both road-owner's and road designer's valuable time in design phase. In period of 2016-2020, around 35000km of state roads were analyzed with one of the most efficient road defects inventory systems in the world. Also, around 25000 km of municipal and forest roads have been captured with same technology covering several pavement types from bicycle paths to multilane streets and motorways. Current presentation discusses outcomes of Estonian defects inventory study in 2020.

In these days constantly being looking for solution to reduce construction costs, the amount of materials used and the negative impact on the environment. Designing pavement structures with top layer of traditional concrete, the structures become very massive. An alternative to traditional concrete is roller-compacted concrete, the concrete with significantly larger fine aggregates which lead concrete mix to be non-slip. The roller-compacted mix can also achieve high concrete density and consolidation by rolling. Roller-compacted concrete is also an economical and fast-construction alternative for many pavement applications. In Lithuania, roller-compacted concrete as the top layer is an innovation and first application of it was few years ago. However, in recent years application of roller-compacted concrete increased in industrial areas and low-volume rural roads. The best practice of application of roller-compacted concrete was in Klaipeda Free Economic Zone, where roller-compacted concrete was used as the top layer of industrial area for heavy load traffic. Fresh roller-compacted concrete workability decreases with time, to reduce transportation time and avoid excessive moisture loss, which can cause problems in placement of roller-compacted concrete, mobile concrete batching plant used. Mobile concrete batching plant was located near construction site.

This research investigated the effect of mineral composition of aggregate on moisture sensitivity of bituminous mixtures and explored the benefits of hydrated lime filler and Wetfix BE surfactant additive to improve the resistance of the mix against moisture sensitivity. Basalt, quartzite, and limestone aggregates were selected based on their different mineralogy and 70 -100 penetration graded bitumen binders used during the study. Four laboratory tests the rolling bottle, shaking abrasion, pull-off tensile strength and indirect tensile strength tests were applied to study the effects of aggregate minerals and benefits of hydrated lime and Wetfix BE. Statistical analysis using Two-way ANOVA test conducted for each test to check the outcome significance. Results from each test revealed that mineral composition of aggregate have significant effects on the moisture resistance performance of bituminous mixtures and hydrated lime filler and Wetfix BE surfactant additives have advantages to improve the performance of bituminous mixture against moisture sensitivity and improves the long-term performance of asphalt mix.

In the last few years as the road construction budget has been decreasing in Latvia, the number of road construction reinforcement design and construction objects has been increasing. At the beginning of the project development of the existing road condition is assessed, taking into account various pavement evaluation criteria and it is determined on which road sections it is possible to reinforce the pavement and where full construction is required. The road pavement structure in Latvia is developed using "Recommendations for road design. Pavement" and inaccurately defining the bearing capacity of the existing foundation can significantly affect the service life of the designed structure. During the construction of the road, establishing that the bearing capacity of the existing foundation is lower than specified in the project incurs additional costs for the customer. Project changes are made, and special solutions are provided in order to achieve the bearing capacity on the mineral material layers defined in the project. One of the most accurate ways to determine the bearing capacity of existing road structural layers is the static plate test. However, the results of this test are also not 100% accurate and any of them may give unreasonable results due to various influencing factors. The aim of this work is to analyze the results of static plate test by determining the most important factors that affect the obtained load-bearing capacity values, identify biased/erroneous test results, and determine which results reflect the residual load-bearing capacity of the existing road structure.

Mineral resources and aggregates used in transport infrastructure or any other purposes importance is undeniable. Its usage and extraction not only benefits economics and social environment, but also should be sustainable. Regarding to this, analysis of Baltic countries mineral resources and aggregates extraction was conducted. The main purpose of the article is to analyze mineral resources situation in each of the country and provide extraction data for aggregates used in transport infrastructure. Mining and quarrying sector is evaluated in whole country economic picture and period 2008-2020 was analyzed by combining data from all the Baltic countries for aggregates extraction. The article is valuable by putting all Baltic countries in one perspective and sharing newest data. Further investigations could include analysis of factors for aggregates demand and its forecast.

This paper presents the results of tests on a damaged pavement made of flamed granite slabs. Due to their architectural value, the use of such pavements made of stone materials is a popular trend in Europe, especially in historic city centres. Faming is a popular method of surface treatment of stone elements, including slabs. The use of flame with a temperature around 1300°C on granite rock leads to allotropic transformations of quartz. The accompanying volume changes lead to flaking of the surface. As a result, the flaming gives the slab a natural texture and improves its anti-slip properties. As it was assessed, most slabs used in pavements exhibited characteristic edge and corner damage. Examination of the mechanical properties of rock taken from a slab revealed different results for samples taken from the high temperature impact zone and from other parts of the slab. The mineralogical tests carried out on samples from the high temperature impact zone showed changes in relation to the original mineralogical composition of granite, including the presence of glaze. These changes resulted in the accumulation of stresses, especially in the areas of slab edges and corners. The analysis of the test results was made in relation to the lack of uniform European standards for stone treatment by flaming and the lack of control procedures for this process. As a result of unrestricted flaming conditions, the originally homogeneous properties of the rock may vary within a single product and lead to its accelerated degradation during exploitation.

Paving is one of the most crucial stage in the matter of road lifespan, since it is the surface layer that has stand up to all the external factors (weather, traffic etc.). Insufficient pavement density caused by thermal segregation during paving works can reduce the lifespan significantly, especially in Estonian climate (freeze-thaw cycles). Modern technology offers different solutions to reduce the risk of low quality in asphalt production and road paving works. Mobile asphalt plant, feeder and thermo-isolated trailers are some piece of equipment, that contractor can use to level up the minimal required quality requirements. The question is, when to use those and which to use? Moreover, is there any possibility to motivate the contractors to put in some extra effort? In Estonia, motivational bonus-system has been established to encourage innovation and reward the extra effort that has been made for quality improvements. The methodology is based on years of experience gained in different researches and pilot-projects. There are no strict rules for the road paving equipment in the methodology – for example contractor can choose himself either the feeder or/and thermo-insulated trailers are used on not. The main requirement is that the temperatures of entire paving process (surface layer) has been measured and analyzed by special thermographic system. Current presentation discusses the symbiosis of bonus-malus system and development of special thermographic system (TGS Pavement) as a multifunctional tool in asphalt paving in Estonia.

In the European Union, about 30–40 million tonnes of residues known as municipal solid waste incinerator (MSWI) bottom ash is generated and landfilled annually. To address the continuous growth of landfills and to implement zero waste and circular economy policies, researchers are researching ways to turn MSWI bottom ash into a useable resource. The conducted studies show that MSWI bottom ash is suitable for civil engineering, especially for roads, however there is a lack of field studies. As a result, MSWI bottom ash was used to construct unbound base course in heavy vehicles parking lot in 2018 and two pedestrian paths in 2018 and 2020 in Vilnius (Lithuania). This paper focuses on the structures composition and performance of those unbound base courses in terms of stability of particle size distribution, bearing capacity and permeability. The conducted study showed promising results for MSWI bottom ash as aggregate (mixture) to construct unbound base course.

Nanotechnologies have gradually penetrated to the field of bitumen modification especially where durable asphalt mixtures have to be designed. Longer mixing time, higher temperatures or/and higher rotation (shearing) speeds are needed to increase the dispersion of nanoparticles in bitumen. However, this is not necessarily beneficial to the physical and mechanical properties of the final material. As a result, in this study nano-zinc oxide (nano-ZnO) and nano-silica (nano-SiO₂) mixing time for bitumen modification was optimized considering the physical and mechanical properties of the final bitumen. For this purpose bitumen PMB 25/55-60 was modified with nanoparticles at 180 °C using a laboratory high-shear mixer at a rotation speed of 4000 rpm for different modification time selected on the basis of literature review (60 and 90 minutes). Penetration, softening point, viscosity at 135 °C, recovery and non-recoverable creep compliance (multiple stress creep and recovery test) at 60 °C were measured in order to determine the optimal mixing time. The results showed that 60 minutes ensures the dispersion of nano-ZnO and nano-SiO₂ in the bitumen PMB 25/55-60 and longer mixing time do not have a significant effect on the properties of nano-ZnO and nano-SiO₂ modified bitumen (the difference was less than 7%).

The catalogues of standard pavement structures are common way to design road pavements. In 2019, new regulation for the design of standard pavement structures KPT SDK 19 was issued in Lithuania. One of the new requirements require verification of layer thickness of high-class pavement structures. Such verification should be done by internationally approved mechanistic-empirical methods. In addition, it is recommended to use the same methods to adjust the layer thickness of the selected standard pavement structure for lower classes. These calculations are particularly applicable when the design load (ESAL) is at the lower or upper limit of the class range. Vilnius Tech Road Research Institute experts and outsource IT specialists spent two years for the design model ViaStructura development. Web software based on mechanistic-empiric approach include the boundary conditions, based on Austria, the United States and Germany experience and laboratory test results of construction materials. Materials can be selected from created database, which can be simply expanded with the new materials by the user. as Additional function allow comparison of separate designed pavement structures. The article present the concept of the ViaStructura model for the design of flexible pavement structures, reveals its main principles and advantages comparing to the pavement structure selection by the standard catalogue.

In this study, for assessment of surface characteristics, the flow coefficient of coarse aggregates was evaluated as an alternative to the widely used crushed and broken surfaces test. It has been proved that visual assessment is not only time consuming but also inaccurate. The European standard EN 933-5 allows to use of a flow coefficient method according to EN 933-6 as an alternative for the assessment of coarse aggregates, but it does not specify any requirements. Therefore, this study aimed to assess the flow coefficient test and if it could replace tradition visual assessment. In total, 28 gravel samples were tested. Following properties and their influence to flow coefficient were evaluated - flakiness, particle size distribution and amount of crushed and rounded surfaces. The results show that the flow coefficient test could be used as an alternative if the boundaries of the granulometric curves are set.

The road system in Latvia has evolved over time to a complex network of physical structures that include roads, bridges and overpasses, however, in large it consists of narrow roads of local significance that follow the existing topography and consist of thin foundation and pavement layers. In-depth geotechnical research of road sections before construction has only been carried out in recent decades, thereby with a certain regularity SLLC "Latvian State Roads" has to deal with low bearing capacity soils under the road foundation. As the recent experience shows, there are sections of roads that in the past were constructed on peat. In 2018 during the reconstruction works of the regional road P32 Augšlgatne – Skrveri a low bearing capacity soil under the road foundation was determined. An additional in-depth geotechnical research showed a bog section with a peat layer at a depth of 10m in a 320 metres long section. Although at that point it was possible to continue the work using simple soil stabilization methods, there were concerns about the longevity of the investment. To stabilize the road foundation, a combination of gravel columns and unreinforced concrete pile columns was used. A total of 952 columns were constructed. The aim of this paper is to share technical information and our good practice of road design and construction on low bearing capacity soils using piling method, and it gives a summary of field observations, geotechnical research, design considerations and risk management assessments that were carried out in this specific case. The positive outcome of this case led to a number of future projects where similar methods for load bearing capacity improvement were planned and used.

Plate load test is a widely used method in Latvia both in quality control and in road design process. This test is performed according to the standard DIN 18134. Such test usually takes at least 30 minutes and requires certain load weight. Considering the relatively long time needed for this test, alternatives were sought and a potential alternative was defined to perform testing with Falling Weight Deflectometre (FWD). In order to check this assumption both direct and indirect testing was performed and correlation between the results of both tests was defined.

In the first case the test was performed in the same location with both pieces of equipment on a surface of unbound pavement. In the second case the test with Falling Weight Deflectometre was performed on the surface of bituminous pavement but plate load test was performed in the same location on the surface of base course with prior demolition of bituminous layers. In order to compare the results of indirect comparative testing, the backcalculation for the data acquired with Falling Weight Deflectometre was performed according to German calculation method.

Results acquired with direct testing showed that the testing with Falling Weight Deflectometre and plate load test are interchangeable if no characterization of the layer compaction is required. The German method of backcalculation (FGSV, 2014) is very simple. Despite positive references from other specialists this method in comparative testing did not show sufficiently good correlation with the results acquired in plate load test.

Mix design procedure for asphalt mixtures in the Baltic region requires to ensure resistance to low temperatures due to climatic conditions. Thermal Stress Restrained Specimen Test (TSRST) has been considered as the most precise direct test method to determine the thermal behaviour of asphalt mixtures. As the TSRST test is time-consuming and the equipment is much more expensive, therefore the possibility to use Semi-Circular Bending (SCB) as a preliminary test was evaluated and the potential threshold was recommended. This study presents the evaluation of low-temperature properties with SCB and TSRST methods and the test suitability assessment for use in quality control. The supplementary rating was made by analysing Fraass breaking point test results of asphalt binders. In total 36 different asphalt samples were tested to investigate fracture test methods and to assess the influence of bitumen type and composition on resistance to low-temperature cracking. The results displayed an acceptable correlation between both test methods that allow using SCB for pre-screening purposes. At the same time, the results indicated that the type of used bitumen has a crucial influence on asphalt mixtures resistance to low-temperature cracking.

The formation of snow cover has been unsustainable in recent decades, which means that freezing and thawing are becoming more frequent in Latvia and that is one of the reasons why asphalt concrete frost resistance matters. Asphalt concrete beams were exposed to multiple freeze-thaw cycles and afterwards tested on a 4-point bending test for stiffness and fatigue resistance. Frost resistance testing for aggregates and concrete is a popular and widely described and used test method worldwide, but there is no such testing standard for asphalt concrete. This study is aimed to develop a methodology for determining the frost resistance of asphalt concrete by adapting the requirements of cement concrete standart AASHTO C666, as well as to experimentally evaluate the effect of frost resistance on the fatigue strenght and stiffness of asphalt concrete. The results show significant correlation between asphalt concrete void content and fatigue life after multiple freeze-thaw cycles and correlation between the amount of freeze-thaw cycles and asphalt concrete fatigue life.

The use of hexagonal geogrids in pavement structures results in the increase of the life of designed structure.

This offers the possibility to reduce the thickness of layers without reduction of pavement life, or to increase the traffic capacity of a pavement without the need to increase its thickness. This way of using geogrids in pavements design was introduced to the pavement industry by one producer of hexagonal geogrids as a Pavement Optimisation (PO) concept.

It can be transformed into both economic and environmental benefits, and obviously results in savings of natural resources and reduction of carbon footprint of a project. PO with geogrids can be used both in the newly designed pavement structures, and in the asphalt overlays of the existing old pavements. Asphalt overlays enhancement with a geogrid either increases the fatigue life of overlays or allows the reduction of overlays thickness to achieve the same pavement life. In new pavements, stabilisation of aggregate base with geogrids increases the stiffness of aggregate, which increases the performance of a whole pavement. This paper presents several tests results, which confirm beneficial effects of using hexagonal geogrids in asphalt overlays and aggregate base layers, from laboratory to full scale accelerated pavement tests. Also, modifications of Mechanistic-Empirical pavement design method, which allow to implement the geogrid benefits into the design process, are discussed. Finally, case studies of pavements – newly designed and reconstructed – optimised with hexagonal geogrids are presented.

High content reclaimed asphalt (RA) mixtures have been identified as one of the options to reduce the environmental and economic impacts of pavements construction. However, the process of designing and producing high content RA mixtures is challenging and the asphalt industry have serious concerns towards quality and long-term performance these mixtures. In laboratory, several parameters affect mixture characteristic, and if not controlled, may results into inaccurate estimation of performance. This state- of-the-art study aims to identify critical parameters for high content RA mixture production and highlight the effects of these parameters on mixture performance. The mixing parameters adopted in several laboratory studies have been highlighted and compared. The best practices to mix recycled asphalt in laboratory are reviewed in order to optimize the laboratory mixing. Based on review, important considerations for evaluating laboratory performance have been discussed.

Tire/pavement noise is one of the biggest environmental problems caused by the contact between the car tire and the pavement surface. It is known that porous asphalt (PA) pavements has good properties in noise absorption, however these mixtures could also solve another important problem which appear on roads – aquaplaning. This phenomenon reduces traffic safety and driving comfort. Aquaplaning appears when tires become separated from the pavement surface by thin water film and the ability to increase braking force or control the vehicle motion is almost entirely lost. Although, PA pavements have relatively low durability properties. This research aims analyse surface texture and permeability characteristics of aquaplaning resistant asphalt pavements. Four different mixtures with different largest particle size (AT 5, AT 8, AT 11 and AT 16) were tested. Large-scale laboratory testing was performed to evaluate their surface texture and permeability properties The research revealed, that mixtures with 8 % activated mineral limestone powder (AMLP) showed better mechanical and physical properties than comparing to other mixtures with 4 % AMLP and 4 % granite screenings or just 4 % AMLP.

This paper collects all the existing swing bridges around the world to emphasize the high-level technology performed in the earliest 20th century and analyzes the recent experience in the rehabilitation and retrofitting of a singular swing steel bridge.

The bridge over the Asón estuary at Treto, in the North of Spain, showed significant problems and the structural condition level was critical previously to its intervention in 2015. The rehabilitation project including the restoration of the structural and functional safety level of the structure was deled after material studies and tests were performed. The new updated of the structure from the old nineteenth centuries to the new standard codes was also performed. A part from the historical value of the bridges and the "green" and safe-security aspects, the intervention took into account all the social requirements of the population in the area who recovered the pride in this emblematic and centenarian infrastructure and it is, itself, a successful intervention from the resilient point of view.

Bridges are one of the most expensive elements of the road network, and therefore in the bridge management process, it is very important to make the most technically efficient and cost-effective decisions about planned actions such as maintenance, rehabilitation and reconstruction works. Decisions have to be based both on the current situation and possible future options and alternatives.

The European Cooperation in Science and Technology (COST) during the action TU 1406 "Quality specifications for roadway bridges, standardization at a European level (BridgeSpecs)" in the period from 2014 to 2019 has developed the framework for the development of bridge Quality Control Plans (QCP) including the system of data collection, data processing and outcomes.

This article analyses and compares different Quality Control Plans developed according to COST TU 1406 methodology for the existing bridge over the river Maza Jugla, located on regional road P10 at km 34.80 in Latvia.

On the 20th July 2018, it was the 50th anniversary of the day when the Lorupe viaduct was opened. Its idea, design and construction were a significant turning point in bridge construction in the whole Soviet Union. In the comparatively small Republic of Latvia it was a unique project that required a lot of boldness and skills of road workers. Therefore, construction of this bridge is memorable, especially since several bridges were built using this technology later in the former Soviet Union. Latvian road workers with their courage, creative and meticulous work implemented a European scale project in difficult, constrained circumstances.

The paper reviews the United States and Slovenian safety factor calculation methodologies and proposes a method for more accurate estimation of residual strength of bridges designed and built in Lithuania. For more detailed analysis, the main parameters and defects directly affecting the strength of the bridges were analysed in detail, and the flows of heavy vehicles, which have significantly increased for previously designed bridges, were assessed.

This article proposes to calculate the dynamic factor of bridges, not according to the empirical formulas used in the United States and Slovenian safety factor calculation methodologies, but after performing the bridge dynamic test, because the results of Lithuanian bridge dynamic tests show that the parameter strongly depends on smoothness and damage of carriageway wearing surface. In order to evaluate the suitability of the Lithuanian bridge safety factor calculation methodology proposed in this article, a real bridge was selected, and its safety factors calculated according to the above mentioned and proposed methodology and the results obtained were compared.

Road inspection regularity and existing types made by road maintenance crew have not been good enough to be aware what is really happening on the roads. Road users' contribution in road traffic safety is very important to ensure fast reaction on different road hazards.

It is important to ensure not only the most common ways to report road hazards on state roads by phone, by email and on social media, but also expand data sources options in modern and user-friendly way.

Waze navigation application already had functionality to report road hazards – to warn other application users, but no one acted to solve these road hazards until someone reported them through existing communication channels supported by Latvian State roads or Latvian road maintainer.

To ensure better road traffic safety and faster reaction time on road hazards solving, Latvian road maintainer gained access to Waze report feed, and, in corporation with Riga Technical university, made a system for analysing and processing Waze data. As the result - Latvian roads maintainer can improve road safety by faster reaction to road hazards reported by Waze users.

Today, up to 70 % from total reports processed by Latvian road maintainer are generated by Waze.

According to the data of the European Road Safety Observatory, around 21% of all road fatalities are suffered by pedestrians in the EU. In 2019 in Hungary, road accidents of pedestrians have had a share of 14,6% in all road accidents with personal injuries, which meant 2535 accidents in which one or more pedestrians were injured. A significant proportion of the accidents occurred at designated pedestrian crossings (43,1% of pedestrian accidents in 2019), and this trend increased over the last 5 years. To account the problem, Institute for Transport Sciences Non-profit Ltd. conducted a research focusing on the identification of potential risk factors which may have a negative impact on the level of traffic safety of designated pedestrian crossings in urban areas. Analysis and ranking of the risk factors have been carried out based on experts' evaluation and scoring, with the use of statistical methods. The results of the work explore the risks that need to be addressed with special attention during the review of existing, and the establishment of new pedestrian crossings.

It is well known that camera and video sensors have limitations in detecting pavement markings under certain conditions e.g. glare from sunlight or other vehicles, rain, fog etc. First generations of lane keeping systems depend on visual light. Erroneous detection is also resulting from irregular road surfaces such as glossy bitumen sealing strips, rain puddles or simply worn asphalt. The role of higher performing markings and better visual camera detection has been studied with Vedecom France. LiDAR (light detection and ranging) technology could help to fill remaining gaps, as it actively sends out IR (infrared) light, that returns reliable images of the road scenario and pavement markings both day and nighttime. In order to evaluate the opportunities of LiDAR technology for the detection of road markings, 3M Company and the University of Applied Sciences in Dresden decided to work together in a joint research project. All-Weather Elements AWE, are the latest development of high-performance optics, using high index beads to provide reflectivity both in dry and wet condition. It could be determined that high performance markings help to increase the level of detection by both camera and LiDAR sensors. The AWE marking was detected from significantly longer distances, especially in wet and rainy conditions. In combination with common camera based LKA and LDW systems, the LiDAR sensors can increase the overall detection rate of pavement markings. This is especially important for vehicles with higher SAE levels of automated driving and can support the overall safety of vehicles. The research also evaluated existing test methods for wet and rain reflectivity in EN 1436 and ASTM E 2832 and how measured performance correlates with LiDAR detection.

The highest number of road accidents occurs at junctions. One of the aims of traffic organisation is to improve traffic safety in these areas. Based on a variety of indices – road capacity, points of conflict, number, and severity of road traffic accidents – different alternatives for junctions are evaluated. However, the road network has many junctions and roads serve to travel from point "A" to point "B" at a given time. Therefore, one of the most important tasks when addressing the issue of road safety is to find a rational way of improving the safety without losing the importance of the road. The aim of this paper is to analyse the impact of different junctions on the road network and basing on actual data develop a method for the evaluation of different types of junctions with respect to road class.

LED-based billboards are becoming increasingly popular due to their low cost, flexibility, and efficiency. On another side, the too-bright digital billboard may pose a potential threat to road safety. The driver's perception of advertising depends on the different factors, including the billboard's luminance value. The aim of the study was to develop the assessment method for the digital screen parameters (luminance or illumination) which could be applied by supervising authorities, using budget-friendly devices, such as a lux meter and could be used during the billboard active operation. We tested the recommended method of OAAA and concluded that it is not applied for large billboards (over 25 square-meter) due to the calculated far distance and low sensitivity of lux meter. We have developed the new method based on driver discomfort glare and De Boer ratio. The ratio helps to determine how likely a display is to cause discomfort to those around it. The lower the value, the less discomfort the driver will experience from the billboard. The new method is applied for the active and different size billboard and using lux meter that is not an expensive device. Moreover, we take into account the glare effect of billboard on drivers' vision.

Nowadays outdoor advertising displays have become popular. Bright displays near the roads could cause drivers to experience disability or discomfort glare, especially at night. Disability glare increases with age, but discomfort glare thresholds are independent of age. The aim of the study was to assess a luminance level of displays, which causes glare for younger and older subjects. 24 young subjects age of 20 to 24 years and 13 older subjects age of 55 to 69 years participated in the study. The task was by using the method of adjustment to find out the acceptable level of display brightness when the recognition of high (>90%) contrast objects was comfortable. Measurements were done in a photopic and mesopic lighting conditions. Results showed that discomfort glare were larger in mesopic than in photopic lighting conditions (p < 0.001) for both age groups. Preferred display brightness in both lighting conditions did not significantly differ between age groups (p > 0.05). We can conclude that discomfort glare thresholds for displays with textual elements are independent of age.

Road Weather Stations (RWS) have been extensively used for collecting information about slippery road conditions during the last thirty years. Recently, vehicle based mobile road condition monitors have challenged the fixed RWS. Both approaches have their advantages and can complete each other. Fixed RWS can provide accurate trend data whereas mobile condition monitors can cover the road sections between RWS. Nevertheless, a traditional RWS is a fairly expensive investment, typically 30 000 € or much more, and often includes a number of components not essential for the purpose of measuring and predicting road conditions. To reduce the total cost we have developed a bare minimum of a fixed RWS including only the essential sensor information like road surface state, friction, water and frozen layer thickness, air temperature, road surface temperature, dew point temperature, atmospheric pressure, wind speed and estimated ground temperature at -6 cm. The targeted end user price of the station is one third of the traditional price level. We report experiences with the first installations during 2020-2021.

This article is based on my Master's Thesis entitled "Planning of the Road Maintenance Termstock in Estonian", which examines the current situation of the road maintenance terms. Road maintenance influences every single person and therefore it is important that terms and concepts are clear and precise. I will give a review of the condition of the Estonian road maintenance terms, using legislation, instructions and other materials which are used to regulate the area, and a web questionnaire was carried out among this field's experts. This is the first time when such a thorough study has been carried out about the road maintenance termstock. All the results indicate that there is a need to plan road maintenance termstock in Estonian. Experts who had been questioned, pointed out that there is a need for common termstsock that all parties would have a common understanding of concept definitions and what terms denote them. Most frequently emerging problems were following: terms do not have clear concept definitions; many synonymous terms for one concept; no consistent use of terms in legislation nor in the guidelines; terms systematization has not been taken fully into account; ambiguous terms are in use; lack of termstock that would cover needed terms and have correct concept definitions.

Three Baltic states are located next to each other on the coast of the Baltic Sea. Similarly, to Finland, density of population in these countries is low. All three countries have large amount of state roads with low traffic intensity.

Climatic differences are minimal. Milder climate is in coastal area but inland the weather conditions are more severe. The average air temperature in January in Estonia is from -2 to -7 degrees Celsius but in Lithuania from -1 to -5 degrees Celsius. The number of snowy days fluctuates from 50 to 120.

All three countries have common contracts for summer and winter maintenance where the responsibility for maintenance activities lays on the contractors. Despite common history the methods of the assignment of road maintenance contracts are different in every country. Estonia awards contracts in open tenders and has performance-based contracts. Latvia has the contract awarded to the State Joint Stock Company «Latvijas autoceļu uzturētājs» ("Latvian Road Maintainer") by law and the contract is unit price based. Lithuania has the contract awarded to the state-owned company « Kelių priežiūra» the contract is performance-based.

The requirements for road conditions are quite similar in all three countries. They have three levels of maintenance.

High service level means snow and ice-free surface of the road pavement during winter in constant weather conditions and quick response in case of worsening road conditions.

Medium service level means that snow and ice is allowed on the surface, but activities must be undertaken to improve skid resistance. The lowest service level means that snow and ice is allowed on the surface and activities to improve skid resistance (mostly only snow cleaning) may be undertaken in some spots only.

In Estonia the expenses for winter maintenance are lower than in the neighbouring countries but it does not have impact on traffic safety during winter.

Since the end of 2017 the Lithuanian Road Administration (LRA) has taken over the authority to issue permits for oversized and heavy vehicles using the national significance roads from the former State Road Transport Inspectorate. LRA has launched a pilot project for automated authorising system, in which application is submitted by filling electronic form and providing a driving route on a map. The route in most cases is automatically approved by the system. If there are any restrictions on the route or in case of larger parameters of a vehicle, an LRA specialist shall review it. Upon coordination, the system automatically calculates a charge for the use of roads by abnormal transport and informs the applicant. The applicant pays this charge via electronic banking, and the system automatically issues a permit (such payments make up to 90 %). If the charge is paid by standard transfer, the system automatically issues a permit after LRA employee registers payment details.

Estonian Transport Administration (ETA) has since 2010y developed digital solutions for monitoring abnormal 52t transport heavy vehicles (HV). Since 2020y we signed the memorandum between 8 different parties for developing bulk material transport digital solutions (e-waybill system) for road building. The focus is to make the logistic more transparent since beginning of the loading point - for the different authorities. The second focus is to make the truck movement corridor visible for the traffic control, avoiding week roads, bridges etc. The final, and the most difficult, is to develop the mass control system, so that there is automated weight info in the e-waybill system visible for the traffic police and for building supervisors etc. We have met with our Association of Estonian Cities and Municipalities and many others, and everyone is very interested of going from paper waybills for faster, cloud based, e-waybill systems, what is also more C02 friendly. This digital e-waybill allows single data entry, and all the rest data with statistics is visible for concerned people. ETA is planning to pilot in 2021y also many road building projects with e-waybill demand. So far, the feedback has been mainly positive from different parties. We have started with our Estonian Ministry of Economic Affairs and Communications (EMEAC) also wider digitalisation projects concerning the new regulation (EU) 2020/1056 of eFTI for the gross-border transport logistics digitalisation, what must be applied in every member state 21.08.24.

In 2020 the Lithuanian Government approved traffic safety programme Vision Zero. One of the integral measures applied to improve traffic safety and to reduce the number of road traffic infringements is the development of average speed cameras' network on state significance roads. It is planned that the network of average speed cameras will cover more than 800 km of state significance road network in Lithuania in 2020-2021. Initially, it was planned to implement these measures only on rural roads. However, taking into consideration the principles of road eligibility for average speed camera installation, some road sections crossing the so-called linear settlements were selected to test the impact of such systems on driving habits as well. It is presumed that from the beginning of exploitation of these systems the reduction in the consequences of severe traffic accidents on the selected most dangerous state significance road sections will be observed.

Intelligent transportation systems (ITS) provide significant added value to road transportation, making the related investments distinctively effective and long-lasting. Moreover, some ITS activities may be eligible for financial support of the European union (EU). That was the way how Estonian Transport Administration and Latvian State Roads worked on the project proposal "Smart corridor Tallinn-Tartu-Luhamaa-Riga E263/E77" (acronym – SMART E263/E77), which was approved by EU program Interreg Central Baltics as CB891 project. The project started on June 1, 2020, and its implementation will last till the end of 2022 according to quite challenging schedule. Project activities primarily include numerous installations or road telemetry and telematics devices (especially, variable message signs) for advanced traffic management to be supported by cross-border traffic plans and improvements of traffic control centers. Project target is to provide general travel time savings at least by 0.88% across the whole corridor, however for the motorway-type sections it should reach more than 5.5%. Expected project results will establish new and improve existing functions on the E263 and E77 road transport corridors, namely: traffic management adaptive to variable road conditions; gathering and dissemination of traffic information; decision-making support for road maintenance operations (especially in winter). This report will summarize the information on project progress with emphasis on traffic management considerations.

Electronic construction journal (later – e-journal) has been developed to replace a former paper construction journal. The purpose of e-journal is to ensure effective supervision of road construction and reconstruction works and to avoid potential abuse. Records made by contractors, supervisors and controlling institutions in e-journal enable to manage the work process in each road construction and reconstruction building site. All road construction process participants have access to the data, comments and findings entered into e-journal. E-journal accurately records all deadlines, technical supervision or control performance time. It is a significantly faster and more effective means of control and quality assurance of performed works.

BIM is an integrated set of building design, construction and management processes, technologies and regulations that allow all parties involved to jointly design, build and manage a building in a digital environment.

In Europe, a common approach to the use and adaptation of technologies is currently being developed with the aim of providing a common regulatory framework that would promote the efficiency of technology application between the countries of the European Union. The use of BIM technologies is based on economic (financial) benefits. The financial benefits are estimated in the long run, and the main factors for financial savings are productivity and quality, which can be achieved by applying BIM technology and appropriate processes during the construction cycle (design, construction and management). Studies show that savings can reach up to 10% of construction costs.

Currently underway is the process of implementing and configuring the Microsoft Dynamics platform for processing and using work information of SJSC "Latvian State Roads" (LSR). Microsoft Dynamics is a line of enterprise resource planning and customer relationship management software.

In general, LSR intends to use the system in the following stages of the construction cycle:

• Design stage

• Construction procurement stage

• Construction stage

• Warranty period

Microsoft Dynamic has both pros and cons for processing LSR information. Only after full implementation it will be possible to assess the effectiveness of this platform.

Objective of the article is to explore how the use of BIM can improve the LSR work process and what happening at this moment in LSR.

Digitalisation is the key to efficiency in the road construction Industry. Building Information Management (BIM), being the main developments in the architecture, engineering, and construction (AEC) Industry, offers a technology as well as processes to bring traditional design and construction practices to the digital era. Estonian Road Administration started the process of BIM implementation to the Estonian road Industry in 2017, when the first planning of pilot projects began. Today, the utilisation of BIM is set as a strategic goal for Estonian Transport Administration (formerly Estonian Road Administration) and a structured approach has been developed in order to overcome such a complex shift in the ways, how road information is being managed in the whole life cycle of a road. Development of principles of data movement, setting technical guidelines and requirements, managing legal issues and communication within the organisation, as well as outside, training of personnel are all aspects that need to be taken into consideration. Successful adaption also needs good communication with the Industry, which is mainly done with Estonian Digital Construction Cluster – a collaboration which brings together the main stakeholders in the sector. In a few years time most of the main sections of the road life cycle will hopefully utilise BIM successfully in Estonia, but the key lies within a well developed and excecuted implementation. The paper describes the development of such a implementation plan and also brings out the main issues and success factors, that are relevant for a successful shift towards digitalisation in the road construction industry.

Besides all the positive characteristics of cement bound courses (CBC), it has some detrimental effects on the pavement wearing courses. Due to cement hydration, this mixture is affected by shrinkage. Shrinkage induces cracks in the whole layer which along with weather conditions propagate through asphalt layers in a short period. Also, it's stiffness negatively affects cracks propagation without providing elastic support for upper layers. As a result, roads are covered with various damages which reduces driving comfort and safety and demand new financial investments. The focus is on reducing the detrimental effect of CBC on the pavement. Nowadays, large quantities of recycled rubber can be found on the market. Wasted rubber is a large ecological problem due to its long decomposition period. On the other hand, by mechanical grinding and separation process, suitable fractions of rubber can be obtained for use in construction. Consequently, the replacement of conventional material by crumb rubber reduces the consumption of natural material and energy for its exploitation. Appropriate amounts and fractions of recycled rubber have the potential to reduce shrinkage and increase the elasticity of CBC. Within this paper, preliminary research results will be presented on the possibilities of crumb rubber implementation in CBC and its effects on mechanical characteristics. By using recycled materials in construction processes we undertake a major step in the sustainable management of natural resources.

Stabilized mixes that are used in pavement structures are composed of aggregate bound with hydraulic binders (cement, lime) or bitumen. The most commonly used for the construction of base layers are mixes stabilized with cement. A long-standing construction practice for pavement structures was based on the use of quality granular materials for the construction of base layers. However, when designing the pavement structure and selecting materials, economy, sustainability, and environmental impact, in addition to their mechanical properties, should also be considered. Clear requirements and guidelines for sustainable development have imposed the need to explore the possibility of using non-standard materials in construction. Wood ash, which is formed as a residue from the combustion of biomass in the production of electricity and heat, is one of the newer and, in Croatia, less researched alternative materials that can be applied in construction. The paper describes compressive strength tests of mixtures of sand from the Drava River and cyclone wood ash stabilized with various contents of cement. The obtained results showed that with wood fly ash (in a content of 30 % mass.) in the stabilization mixture of sand, values of compressive strengths can be achieved within the required limits necessary for the construction of base layers of the pavement structure stabilized by a hydraulic binder.