1 The XXVIII International Baltic Road Conference TRAFFIC MONITORING AND WEIGH-IN-MOTION SYSTEM FOR LITHUANIAN ROAD NETWORK Tadas Andriejauskas 1, Audrius Vaitkus 2, Aja Tumavičė 3 1,2,3 Road Research Institute, Vilnius Gediminas Technical University, Vilnius, Lithuania 1 Linkmenu str. 28, LT Vilnius, 2 Linkmenu str. 28, LT Vilnius, 3 Linkmenu str. 28, LT Vilnius, Abstract. The article gives a study of a heavy vehicle overweight problem in Lithuanian road network. Paper will provide reader with definition of theoretical and implementation models of traffic monitoring and weigh-in-motion (WIM) system for Lithuanian road network. According to these models, an evaluation has been made of the optimal need for WIM systems, defined road geometry and pavement structure requirements for site selection and performed a field research. With regards to the research results, article contains a submission of requirements for WIM system and an alternative suggestions for road pavement structure. Keywords. Weigh-in-motion (WIM), traffic monitoring, pavement structure INTRODUCTION During the period of , there was ascertained a rapid increase of a number of vehicles, especially heavy, that crossed Lithuanian borders. The largest increase was stated after the Lithuania s admission to the European Union, when increased inevitability of trasmitted wheel load to the road structure made a several times higher negative impact to the road pavement structures. According to the recent studies, about 25 % of heavy vehicles travelling with an above the maximum allowable gross vehicle weight and/or axial loads, resulting with the annual damage done to the road infrastructure up to 180 million Lt. The number of recorded violations to the scale of the infringement is small in 2011 State Road Transport Inspectorate under the Ministry of Transport and Communications weighed and measured 6155 heavy vehicles through mobile vehicle weight control, and 1556 of them were issued with a violation of administrative law for exceeding the allowable maximum axle load, gross vehicle weight or dimensions. Along with the overloaded heavy vehicle problem, there is also a large number of cars without technical vehicle inspection or compulsory third party motor liability insurance. In 2011 there was identified violations when driving without a technical vehicle inspection and violations when driving without a compulsory motor third party liability insurance. It was also recorded a lot of speeding violations in 2011 was identified cases of speeding. One of the ways to solve these relevant problems is implementation of a fully automated complex traffic monitoring and weigh-in-motion system in Lithuanian road network. 1 IMPACT OF HEAVY VEHICLES 1.1. Impact on roads Vehicular traffic, especially heavy, has a damaging effect on bridge and road constructions. Road condition and durability is directly dependent on the number of passing vehicles, number of axes, loads of axes, gross vehicle weights. Increasing axial load rapidly deteriorates pavement causes cracks, holes, ruts and accelerates the erosion of asphalt pavement. The most critical axial loads are the ones that exceeds the allowable design axial loads. The main factors affecting the pavement deformations are the following (Šiaudinis, Čygas 2007): Increasing volume of heavy vehicles traffic; Increased vehicle axle loads, which often exceed the allowable loads, previously applied to design the roads; Overloaded vehicles exceeding the allowable loads. Road pavement is exposed to multiple short-term and sometimes long-term loads that are transmitted via car wheels. These loads in separate asphalt layers cause stress and the pavement
2 2 The XXVIII International Baltic Road Conference deformation appears (Butkevičius 2007). Loads and stress, arising on pavement structures, are directly dependent on the axle load, wheels on the axle ant tire pressure. In order to protect the roads, there are determined axial load and gross vehicle weight restrictions in Lithuania. Maximum allowable vehicle axle load is 10 tons (main axle 11,5 tons), and gross vehicle weight 40 tons (since 2013, the law, imposing a maximum gross vehicle load of 48 tons, took effect, but only with prior agreement of the routes with a road owner). In order to comply with the restrictions, it is necessary to control vehicle axial loads. The biggest damage to the Lithuanian state roads is made by heavy vehicles, because the effect of their axial loads is much larger than the overall traffic. Impact of passenger cars on the deterioration of asphalt pavements is minimal. Sivilevičius and Šukevičius (2007) states that the biggest damage to the roads is made by overloaded heavy vehicles. It was found that an average 2-axle heavy vehicle makes the damage to the road as much as 500 passenger cars, 5-axle heavy vehicle makes damage as much as passenger cars. Overloaded heavy transport and large volume of traffic are interrelated problems, determining a rapid deterioration of Lithuanian roads. Increasing volume of heavy traffic causes bigger pavement deformations and faster degradation. Due to permanent loads, road surface quickly loses the original strength, resulting ruts and holes, which pose a danger to road safety, particularly when raining (Sokolov, Sivilevičius 2011) Impact on road safety Assessing the influence of overloaded vehicle, an accident factor should be taken into account. Overloaded vehicles are more difficult to control because of limited vehicle maneuverability and stability. This increases the likelihood of accidents and make them more complicated (more fatal and injury accidents). Moreover, overloaded vehicles worsen the quality of roads, making road conditions difficult for other road users (The U.S. Department of Transportation 2000). Vehicle weight has a signifficant effect on the vehicles stopping distance. The heavier the vehicle is, the longer distance it takes to stop (Kulakowski et al. 2004). Moreover, higher vehicle weight leads to earlier depreciation of tyres and brake system. All of it might have a negative effect on traffic accident s frequency and consequences. Expanding flow of traffic increases a probability of accidents, caused by heavy vehicles. Mostly, victims of accidents caused by heavy vehicles are smaller size vehicles and vulnerable road users as pedestrians and cyclists, resulting with significant consequences. Some of these accidents are the result of heavy or overloaded vehicles inability to estimate dimensions of their vehicles and driving speed. Heavy vehicles accidents induce 6 times more injuries compared with accidents caused by another types of vehicles. Research has shown, that increasing the weight of a truck by 3-5 tons, raises a risk of accidents by 20 % respectively. Interdepence stands with regards to vehicle break distance, enlarged dimensions and lower traction Impact on competitiveness The rapid development of the European economy affects the growth of cargo traffic. Strong competition between transport companies stimulates the transportation systems management improvement. Consequently, it leads to optimisation of commercial vehicles use less empty or half loaded heavy vehicles and more fully loaded or overloaded heavy vehicles on the roads. Overloaded vehicles not only damage country s road infrastructure, but also affects natural competitiveness. In France, it was observed that a driver of a 5-axle truck with 20 % overload earns euros more over the year, compared to the truck with allowable load (Jacob, Feypell-de La Beaumelle 2010). Logistic companies violating allowable load limits make fewer routes than fair ones. Estimations made in France show, that exceeding allowable loads by 20 %, large logistic companies can save costs up to 21 %. Consequently, it leads to imperfect competition, what makes a negative impact on cargo transportation prices.
3 The XXVIII International Baltic Road Conference 3 2 ANALYSIS OF VEHICLE WEIGHING SYSTEMS Over the past decades, there was significant growth of heavy traffic in the U.S. and in Europe, that led to increased problem of overloaded and oversized vehicle control. In order to reduce this problem the development of weigh-in-motion (WIM) technology was initiated. This technology allows to define gross vehicle weight and axle load while the vehicle is in motion (Honefanger et al. 2007). Thus, methods of heavy vehicles weighing currently being used in practice are listed below: Static weighing. This weighing method is commonly-used by road traffic inspection for mobile vehicle weight control on a road and border control officers at border control posts. This method requires a huge amount of time resources and labor working hours, since heavy vehicles are being weighed in their completely stationary position. Despite that, this weighing method is considered to be highly accurate (Jacob, Feypell-de La Beaumelle 2010; Wisnicki, Wolnowska 2011). Low speed weigh-in-motion (LS-WIM). This weighing system is similar to static weighing and due to high accuracy it can be used as a tool for imposing sanctions for delinquents. Vehicles are pointed to the special zone near the road and weighted with LS WIM system while driving at speed 5-15 km/h. Accuracy of this weighing method reaches approx. 3-5 % (Jacob, Feypell-de La Beaumelle 2010). High speed weigh-in-motion (HS-WIM).This kind of WIM systems are based on automated vehicles weighing on traffic at the regular speed. The accuracy of these systems is highly dependent on the sensors quality and installation location (Jacob, Feypell-de La Beaumelle 2010; Urgela, Janotka 2008). This type of systems are widely used in the worldwide for statistical information collection and the preliminary weighing (Klashinsky et al. 2010), when HS-WIM systems weigh the vehicle and, in case of violation, direct it to the weighing area next to the road by using reversible traffic lights or active signs. In this area vehicle are weighed using more accurate method (stationary weighing or LS-WIM) (Sokolov, Sivilevičius 2011). In order to increase vehichles weighing control effectiveness, preparation had started of HS-WIM system s complete automatization and direct enforcement (Van Loo, Jacob 2011). Hence, vehicles are being weighed by the installed sensors in the road surface, while driving at a normal speed. In case of overweight, vehicle is recorded by video surveillance cameras with integrated licence plate recognition. Thus, obtained information is used for direct enforcement. Multi-sensor weigh-in-motion (MS-WIM). One of the limitations of WIM system is its inability to estimate dynamic forces of tyres, which occur due to interaction of vehicle and road surface. MS-WIM system is based on a certain number of sensors installed in the road surface and are consistent with a certain algorithm. Each sensor measures axle loads, which vary depending on time and distance (Jacob, Feypell-de La Beaumelle 2010). Bridge weigh-in-motion (B-WIM). This method is based on bridge strains measurement to evaluate traffic loads of passing vehicles. Data from deflection measurement devices and axes sensors is respectively converted into axle load. The algorithm determines vehicle's weight by comparing it with a theoretical measurement model (Quilligan 2003). Currently there are a number of suppliers offering different kind of sensors for weigh-in-motion system. The most commonly-used weighing sensors are: bending plates, load cells, piezoelectric sensors and piezoquartz sensors (O Brien, Leahy 2011). 3 THEORETHICAL MODEL AND IMPLEMENTATION PRINCIPLES OF THE SYSTEM More effective heavy vehicles weight control could be achieved by implementing high speed weigh-in-motion system in Lithuanian road network. Vehicle will be weighed by the sensors installed in the road surface and in case of fixed overload or other violation vehicle will be
4 4 The XXVIII International Baltic Road Conference recognized by video surveillance cameras with integrated licence plate recognition (Fig. 1). For the most efficient use of WIM systems it should be implemented together with traffic monitoring and violation fixation systems. Additionaly, system would be able to identify vehicles with invalid vehicle technical inspection or compulsory motor third party liability insurance, stolen vehicles, speeding violations, etc. Traffic monitoring and violation fixation devices WIM sensors in the road surface Fig. 1. Traffic monitoring and weigh-in-motion system implementation scheme It is planned that a proper HS-WIM system installation in Lithuanian road network would help to significantly reduce the damage caused by heavy vehicles. Practical benefits of the system can be described by theorethical principles of traffic monitoring and weigh-in-motion system: 1. Prevention of overloaded heavy traffic in the Lithuanian state roads; 2. Identification and control of all vehicles in traffic; 3. Gathering of statistical information; 4. Improvement in road safety; 5. Possibility of a future system supplement with additional ITS systems. A proper installation and effective operating of WIM system requires high accuracy conditions and appropriate selection of sites for system posts. According to the COST 323 recomendations the WIM system should meet A (5) and B+ (7) class requirements. Devices of a certain accuracy classes ensure a measurement of gross vehicle weight and axle loads with no more than 10 % error. According to the COST 323 (Jacob et al. 2002) requirements, such a precision is sufficient for WIM systems to be legally used for enforcement of overweight violations and accurate accumulation of statistical information. Selected sites for weighing equipment may have a significant effect on system accuracy. Dynamic forces distribution in vehicle may vary due to pavement, road geometry parameters and other factors. These dynamic forces affect measurement accuracy. In order to properly select location for weigh-in-motion stations was defined certain criteria that the location should satisfy:
5 The XXVIII International Baltic Road Conference 5 1. Traffic volume of heavy vehicles. System stations should be selected at the road sections with most intense heavy traffic, near industrial attractive centers, including the assessment of the possibilities to avoid these weighing stations. 2. Traffic mode and restrictions of heavy traffic or a certain weight restrictions. WIM sites should be selected in these road sections where is no factors that may affect the smooth vehicle speed (intersections with state roads, acceleration/deceleration, speed changes, congestion, etc.). 3. Geometric parameters of a WIM road section should meet COST 323 requirements in a distance of 50 m before and 25 after WIM sensors. 4. Planned road reconstruction or repair works at the road section of WIM station. It is important to gather information about the planned road reconstruction or repair works and take into account what are their design solutions. 5. Electrical and communication facilities for data transmission. Sites should be selected according to the energy and communication connection for data transfer capabilities. 6. Remarks from Lithuanian Road Administration under the Ministry of Transport and Communications and other stakeholders. WIM site selection should be carried out in accordance with the above criteria and in cooperation with the responsible authorities. 7. Pavement parameters of a WIM road section should meet COST 323 requirements in a distance of 200 m before and 50 m after WIM sensors. Implementaton of the prepared theoretical traffic monitoring and weigh-in-motion system into Lithuanian road network is suggested to be executed in two stages. Each of them were provided by selection of preliminary weigh-in-motion sites, with regards to above mentioned selection criteria. In the first stage, the sites were selected for the purpose to control the heavy traffic weights around the five largest Lithuanian cities (Vilnius, Kaunas, Klaipėda, Šiauliai, Panevėžys). This stage requires implementing the system in 39 positions of Lithuanian road network (Fig. 2). First stage implementation enables to control most intensive heavy traffic routes in Lithuanian road network. Implementation of the second stage consists of additional 17 system posts near the international border crossing points and in the strategic locations. Moreover, there will be created an automated weighing network for heavy vehicles, covering the entire territory of Lithuania (Fig. 3), allowing a fundamental control of heavy traffic flow across the country and reducing its damage to the overall road infrastructure. Fig. 2. Traffic monitoring and weigh-in-motion system in Lithuanian road network I implementation stage (left). Lithuanian cities recommended for system implemetation are marked in red. Fig. 3. Traffic monitoring and weigh-in-motion system in Lithuanian road network II implementation stage (right). Locations recommended for systems posts implementation are marked in red.
6 6 The XXVIII International Baltic Road Conference However, considering high technology costs, their novelty, complexity and a lack of suitability testing for Lithuanian conditions, it is recommended to start implementation with an initial installation stage (stage IA) of these devices. At this stage it is recommended to install the 14 system posts around the city of Kaunas and near the international border crossing points. This stage of implementation will enable the assessment of system reliability and a need for additional tools, with regards to all WIM system installation. 4 RESEARCH OF ROAD SECTIONS FOR PRELIMINARY SYSTEM SITES Road Research Institute of the Vilnius Gediminas Technical University carried out a research of 14 preliminary HS-WIM system post location road sections (Sept. Nov. 2012), with the purpose to measure and evaluate existing geometrical and pavement structural parameters of a certain road sections. Research was carried out in three stages. In the first stage a visual inspection of road sections was performed to assess a road section suitability for traffic conditions, terrain and electrical facilities. During the visual inspection, there were also revised intallation sites of preliminary HS-WIM system posts. Second stage included an execution of road geometry and pavement structure measurements. Measurements were carried out by Public Enterprise Road and Transport Research Institute using a mobile road examination laboratory RST 28 and falling weight deflectometer Dynatest 8000 FWD. To assess geometrical parameters evaluation, a topographical surveying photographies were prepared in a distance of 200 m before and 200 m after the preliminary WIM site. Longitudinal slopes and curvature of a road section were measured by using these photographies. Transverse slopes were determined by measuring road surface each meter with a laser profilometer in a distance of 200 m before and 200 after the preliminary WIM site. Laser profilometer was also used to determine pavement structural parameters. Rut depth measurements were performed in all lanes measuring rut depth by every meter. Pavement roughness (IRI) measurements were carried out in all lanes measuring surface roughness by every meter under the left and right wheels. Pavement deflection measurements were performed by measuring all lanes every 10 meters using falling weight delfectometer in a distance of 200 m before and 200 m after the preliminary WIM site. The third stage includes an execution of geological surveys, laboratory tests and determination of asphalt and road construction layers thickness. Geological survey were carried out in one place of a road section of preliminary WIM system post location (center of a road section). Determination of a thickness of asphalt layers were performed by drilling cores in the pavement in three places of a road section (in the center and 75 m on each side of the center). Pavement structure thickness was determined by drilling hole in a center of a road section. Material samples taken asphalt and road construction were further analyzed in the Road Research Laboratory of Vilnius Gediminas Technical University, where determined: Types and thickness of asphalt courses; Type and thickness of base layer; Type, thickness and water permeability of frost-resisting layer; Type, moisture of subgrade. Data and results obtained from a research were analyzed and evaluated according to the COST 323 recommendations. A recommended accuracy class for a traffic monitoring and weigh-in-motion system implementation in Lithuanian road network, which could be used for a legitimate enforcement of weight violations, is the A (5). In case of the requirements of A (5) class are not met, B+ (7) class can be used in certain cases but only with an approval of competent authorities. Road geometry parameters shall meet the requirements in a distance from 50 m (upward to the first weighing sensor), to 25 m (downward the last weighing sensor) for each lane. The road geometry parameters of the system, which is installed in the single carriageway road including both lanes,
7 The XXVIII International Baltic Road Conference 7 shall meet the requirements in a distance of 50 m before and 50 m after the weighing sensors. Pavement structural parameters must satisfy the requirements in a distance from 200 m (upward to the first weighing sensor) to 50 m (downward the last weighing sensor). When the system is installed in the single carriageway road including both lanes, pavement design parameters must satisfy the requirements in a distance of 200 m before and 200 m after the weighing sensors. Measurement results of each road section were the following: Longitudinal road slope requirements (longitudinal slope must be <1 %, and as much as possible constant size) are not met in 3 road sections; Transverse slope requirements (transverse slope must be <3 %, but also has to meet the minimum slope for drainage) are not met in 5 road sections; Road horizontal curve radius requirements (road section should be straight or horizontal curve radius > 1000 m) are met in all road sections; Rut depth requirements (maximum rut depth 4 mm) are not met in all road sections; Pavement roughness (IRI) requirements (international roughness index (IRI), measuring the movement of each wheel path 1.3 m / km) are not met in all road sections except one; Pavement deflection requirements (largest pavement deflection on dynamic 5 t load mm, and the left / right difference ± mm) are not met in all road sections except one; Asphalt thickness requirements (thickness of bonded layers should be greater than 10 cm) are not met in 7 road sections. Performed research of road sections of a preliminary WIM system sites showed, that currently, none of the 14 selected preliminary sites met all requirements of COST 323, regarding a proper quality. Therefore, with the purpose of using WIM system for direct enforcement, it is necessary to reconstruct all road sections before installing the system. According to the research results and evaluation, each road section of preliminary WIM sites were proposed with 3 alternative road constructions. One of the alternatives is an individual road construction recommendation for each WIM site, using the existing pavement construction. Constructions were obtained after bearing capacity calculations in accordance with elastic deflection, using information of the existing pavement structure. Two other recommended road pavement structures are new road constructions with asphalt and concrete pavements. CONCLUSIONS 1. Overloaded heavy vehicles cause serious damage to the bridge and road structures, reduce infrastructure durability, increase operating costs. An increase in the number of accidents and impaired competitiveness among logistic companies are considered as the outcomes of overloaded heavy vehicles. 2. Research provides a reasonable claim, that implementation of 56 traffic monitoring and weigh-in-motion system stations in Lithuanian state roads allows to monitor more intense traffic routes and identify the violators of the traffic rules and other laws of the Republic of Lithuania. Implementation of the system is recommended in two stages (I and II stages), but only with the execution of prior testing in a pilot stage (IA stage). 3. In order to achieve an optimal result, periodic mobile heavy vehicle weight control has to be continued so as limitations for heavy traffic on provincial and local roads using relevant signs. 4. Research of a road sections of 14 preliminary traffic monitoring and weigh-in-motion system indicate that none of the preliminary system sites meet the required A (5) class accuracy requirement. Thus before installing the system it is necessary to reconstruct the road sections. 5. In order to collect A (5) accuracy class data and use it for legal enforcement of the traffic violations it is essential to maintain the required road geometry, bearing capacity (deflection), rutting, IRI value all the system operating time independently of the time of the year,
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