The bonding of asphalt layers has direct reliance on road pavement structures strength and durability. Because of insufficient bond between pavement layers the slippage and corrugations, rutting and cracking occur and the pavement life cycle becomes shorter. The article describes the research on bonding of asphalt layers, which was carried out in 2010-2011 at Vilnius Gediminas Technical University Road Research Institute. In this research the strength of layers bonding was assessed using the direct shear (Leutner) test without normal stress in the specimen. The samples were taken from the road sections of Lithuania with standard asphalt layers, also asphalt layers with the geosynthetic interlayer. The research showed that the bonding strength of asphalt layers of the samples taken on the roads of Lithuania in most cases meets the requirements of standard documents, and the use of geosynthetic materials between asphalt layers worsens their bonding strength.
Winter in Lithuania is the most complicated time of the year to ensure the functioning of transport systems. The main factor which impedes a normal operation of the systems is weather conditions making a direct influence on vehicles and infrastructure elements of transport systems. Precipitation, low air temperature, strong wind and other unfavourable weather conditions impede traffic on the roads and streets. In Lithuania, like in other countries of the world, for the purpose of winter road maintenance (to reduce pavement slipperiness) chemical materials on a basis of chlorides are used (NaCl, CaCl2, NaCl + CaCl2 mixes), the annual amount of which spread on the roads and streets of Lithuania comes to 160 thousand tonnes. Though salts, used for road maintenance, are able to immediately ensure safe traffic conditions, they all have larger or smaller negative impact on the environment which depends on the composition of salts, the amount used and interaction with other environmental components. A negative environmental impact comprises: ground (soil) contamination; water pollution (surface, ground and underground); impact on flora, fauna and human beings; corrosion (of vehicles, roads and reinforced concrete structures); deterioration and deformation of road pavements. Based on the increasing requirements in the field of traffic safety, environmental protection and ecology it is necessary to search for the most effective and less damaging measures to ensure road maintenance in winter: to improve planning and management of winter road maintenance; to implement modern snow cleaning and ice removal technologies; to put into practice preventive road maintenance measures; to use alternative materials and inhibitors which reduce a negative environmental impact.
Growth of towns is a result of citizen's social and physical division. Urban planners and scientists have increased the number of links between urban transport and urban development. Public transport has been in the focus of attention as a sustainable and environmentally sensitive transport that brings environmental benefit and possibility to serve mobility needs of citizens without private cars and reduces social division. The article identifies the main factors that affect the use of public transport in town: land use planning; local government policy; extent of economic resources; implementation of modern technologies; social tendencies. Analysis of the scientific literature has revealed four main models of towns of sustainable urban forms: neo-traditional development, urban restrictions, compact town and ecological town. Vilnius has the formed urban and mono-functional structure with a high imbalance between residential and work places which conditions a high mobility of inhabitants as well as high concentration of transport flows on limited-density street networks between the western residential areas and the central part of the City where the main workplaces are located. It presents the provisions of the Vilnius City Master Plan 2015 concerning the public transport improvement. The article also assesses developments in the public transport network in 2003-2009 resulting from changes in individual routes with regard to passenger time necessary for traveling. Modelling is carried out with the help of VISUM software. Citizens of Buivydiškės and Santariškės are mostly affected by the developments, while the situation in Pavilnys, Aukštieji Paneriai and Tarandė has changed only slightly.
Abstract:Increased traffic flow on low-volume gravel roads and deficiencies of national road infrastructure, are increasingly apparent in Lithuania. Gravel roads do not comply with requirements, resulting in low driving comfort, longer travelling time, faster vehicle amortization, and dustiness. The control of dustiness is one of the most important road maintenance activities on gravel roads. Another important issue is the assurance of required driving comfort and safety. Soft asphalt and Otta Seal technologies were proposed as a sustainable solution for the improvement of low-volume roads in Lithuania. Five gravel roads were constructed with soft asphalt, and 13 gravel roads were sealed with double Otta Seal, in 2012. The main aim of this research was to check soft asphalt and double Otta Seal's ability to self-heal, on the basis of the results of the qualitative visual assessment of pavement defects and distress. The qualitative visual assessment was carried out twice a year following the opening of the rehabilitated road sections. The results confirmed soft asphalt and double Otta Seal's ability to self-heal. The healing effect was more than 13% and 19% on roads with soft asphalt and double Otta Seal, respectively. In addition, on some roads, all cracks observed in spring self-healed during summer.
Gravel roads play an important role in the transport infrastructure. However, their maintenance (especially the control of dustiness using chemical dust suppressants) is expensive. Besides, the condition of gravel roads results in low driving comfort, longer travelling time, faster vehicle amortization, and so forth. Typically, these problems are solved by paving gravel roads with asphalt wearing layer. However, north countries practice had shown pavement structure high susceptibility to frost due to insufficient thickness of frost resistance layer. The construction of thicker frost resistant layer increases road construction cost by 25% and, in most cases, there is no need to increase bearing capacity by increasing total thickness of pavement structure. In 2012 19 gravel roads were constructed using cost effective rehabilitation technologies-soft asphalt and double Otta Seal in Lithuania. This paper focuses on those two technologies' performance within first three years of constructed roads exploitation. The implemented experimental research consisted of three parts by evaluating constructed roads base layers bearing capacity; pavement roughness; and pavement distresses and defects. As a result, the acceptable performance indicators were determined for both technologies-soft asphalt and double Otta Seal. Also recommendations for construction and exploitation improvement were defined.
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