AUTOMATED OVERLOAD ENFORCEMENT BY WIM L-M. COTTINEAU, P. HORNYCH, B. JACOB, F. SCHMIDT Institut français pour les sciences et technologies des transports, de l’aménagement et des réseaux (IFSTTAR), France
[email protected] R. DRONNEAU & E. KLEIN Centre d’étude et d’expertise sur les risques, l’environnement, la mobilité et l’aménagement (CEREMA, DTer Ouest & Est), France ABSTRACT Heavy vehicle overloads contribute to premature deterioration of infrastructure and increase road unsafety and unfair competition between transport modes and operators. Public authorities and road operators must therefore implement an efficient checking system to enforce weights and dimensions at an affordable cost. WIM technologies are widely used for screening overloaded vehicles, and sometime to issue warnings to the violators. However, these systems are mostly not yet approved by the Legal Metrology for automated overload control and fining. With the traffic volume increase, the safety constraints and the downsizing of traffic officer staff, it becomes necessary to introduce automated overload control by WIM. The ongoing Automated Overloads Control (AOC) project, supported by the French Ministry of Transports (DGITM) and carried out by IFSTTAR and CEREMA, aims to demonstrate the feasibility of automated overload enforcement with adapted existing WIM technologies to be certified. The project is carried out in partnership with WIM vendors. Trials have been carried out in lab and on the large pavement testing facility of IFSTTAR in Nantes. Sorting algorithms will be developed to identify the vehicles weighed within the required tolerances and on road trials are planned to demonstrate the feasibility of the whole system. Keywords: heavy vehicle, overload, weigh-in-motion (WIM), automated overload control, direct enforcement. 1. STATE OF THE ART AND CHALLENGES OF AUTOMATED OVERLOAD CONTROL The project builds upon previous results of research works carried out by IFSTTAR and Cerema on WIM, including those carried out since 1996 for the DGITM, allowing the deployment of a WIM network for overload screening [1]. The project also builds upon a literature survey of International experiences on automated overload control (AOC), in order to decide what could be transposed or adapted in France. Today, many countries use WIM for overload screening upstream to checking area, to sort the vehicles to be checked, in static or with low speed (LS-) WIM devices approved by the Legal Metrology. This is commonly done since a long time ago in North America, in Europe, in Australia and New-Zealand, and more recently in Latin America and Asia, or even locally in other regions. The Netherlands and France also combined WIM systems and video cameras, to automatically identify licenses plates of presumed overloaded vehicles, and to perform transport company profiling. Companies with high and repeated numbers of presumed infringements are targeted for warnings and in company checks. -1-
However, the deployment of AOC by high speed (HS-) WIM systems delivering directly penalties began in Taiwan, first in 1998-99 with large tolerances of 30%, enough to enforce the large overloads at that time, and then in 2010-11 with a reduced tolerance of 10%. After 2 years, the number of overloads dramatically decreased, and thus the AOC was suspended. Since 2011 Czech Republic adopted a law authorising the AOC by HSWIM, with tolerances of ±5% for gross vehicle weight (GVW) and ±11% for axle loads. Current statistics show that 65 to 70% of the heavy vehicles are weighed in these tolerances. The first approved systems were installed but some issues remain to be resolved, such as the system reliability, the sorting of vehicles weighed within the tolerances and the implementation of penalties. The requirements in France for AOC, both from a practical, metrological and legal point of view, are the tolerances of the OIML class 5 [2], which correspond to the accuracy class A(5) of the European specifications of WIM by COST323 [3], but for 100% of the measurements instead of 90 to 95% for a non legal application. The ±5% tolerance for GVW is currently accepted for static and LS-WIM instruments approved for enforcement. Increasing this tolerance would likely lead to an increase of overload magnitude, which is currently mostly less than 5 to 10%. It would also not comply with the common practice and the legislation in force on overload enforcement. For axle load, the tolerance may be between ±8 and ±11% (to be defined). However, a HS-WIM system installed on an existing road, cannot weight 100% of the vehicles within these tolerances (at least with the existing technologies). Therefore it is required that the WIM systems automatically identify the vehicles certainly weighed within the tolerances, using only the registered and certified data. Only these vehicles can be automatically penalized. The vehicles presumed being overloaded (measured at a level of confidence between 90 and 95%) will still be screened as usual by the WIM systems. 2. AUTOMATIC OVERLOAD CONTROL (AOC) PROJECT PRESENTATION The objective of the project is to study the feasibility of the automatic overload control (AOC) by WIM and to prepare its certification. IFSTTAR, with the support of CEREMA, is in charge of the technical work packages of the project. The legal aspects are under the responsibility of the DGITM. 2.1. Contents and organization of the project This project includes a central work package on the certification feasibility (WP1), three research and development works packages (WP2 to WP4), a transversal work package on experimental studies (WP EX) containing experiments on road and a work package on assistance and expertise to the DGITM (WP5), as shown in Figure 1. The WP1 aims at deploying procedures for type approval and certification of systems for future AOC, in connection with legal metrology and LNE (National Metrology Laboratory). It will build on the French experience of speeding, spacing and traffic light crossing automated controls. This WP also addresses calibration issues and quality control of the measurements, as well as organizational and legal aspects in connection with the DGITM. Details of practical and functional specifications of AOC will be achieved. Calibration techniques (including automatic self-calibration) of WIM systems will be improved and adapted. New methods and "good weighing" indicators, allowing stations to identify themselves weighed vehicles certainty within the required tolerances will be developed. This work package is in constant interaction with other WPs. -2-
The WP2 has two subsets: (1) the WP2.1 deals with sensor/pavement interactions and aims at analysing the performance of various marketed sensors and characterizing their response in laboratory and on road controlled conditions, depending on the measurement conditions (external factors influencing load measurements); (2) the WP2.2 aims at developing a new optical fibre sensor and WIM system, more efficient and less expensive than the most accurate current systems. The WP3 addresses multiple sensor (MS-)WIM solutions for the AOC, including the design of optimal arrays, methods and information processing tools to sort vehicles weighed within the AOC tolerances. MS-WIM aims at increasing the proportion of vehicles within these tolerances.
Figure 1 – Automated Overload Control (AOC) project organization by WPs The WP4 aims at making a bridge (B-)WIM system operational. Such a B-WIM, including working on concrete frames bridges and orthotropic steel bridges, should meet the AOC requirements. Its adaptation to other types of structures (e.g. girder bridges) is also expected. The WP EX contains road trials, including choice and instrumentation of test sites, realization of test plans, data collection and first analysis, in partnership with the checking bodies (police, DREALs/Services transport), system suppliers and road operators (DIR motorway companies). The WP5 contains the technical assistance and expertise on WIM and AOC for the DGITM. 2.2. Project schedule The project is organized in two phases of 24 months: the first phase started in January 2014 and intends testing the feasibility of the AOC by WIM and overcoming the technological obstacles, particularly with regard to achieving an AOC WIM system meeting the required performance at a reasonable cost, by: - validating the repeatability and reproducibility of the selected and in pavement mounted sensor response, with a suitable signal processing and potential correction of external -3-
factors effects; - assessing the homogeneous functioning of a multiple sensor array; - studying the feasibility (cost and performance) of an optical fibre WIM system; - qualifying a B-WIM system for AOC, for integral slab bridges and orthotropic steel bridges; - developing a self-calibration and built-in sorting algorithms to identify the vehicles weighed within the required tolerance of AOC; - setting the principles of a type approval and certification procedure for the WIM equipments to be used for the AOC, according to the defined specifications. The phase 2 depends on the results of the phase 1, and will continue working towards a fully operational AOC solution by WIM deployable in France, including: - choice of optimal types and numbers of sensors, of their configuration depending on the control sites, on traffic and environmental conditions, on the minimum rate of vehicle to be checked, and on the available financial resources; - definition of the bridge types to be instrumented and of the configurations adapted to AOC, appropriate data analyses, and if necessary development of a new specific B-WIM system. Such a system would then be subject to type approval and pre certification tests, involving legal metrology to identify potential deficiencies to be corrected; - solutions to organizational and legal problems deploying an AOC by WIM system in accordance with the National legislation. With the support of the Ministry of Transport, of Euro Control Route (ECR) and TISPOL, IFSTTAR try initiating a coordinated European action to involve other Member States in the process, to harmonize the European frame for AOC aligned with the revised Directive 96/53EC, and to share National R & D resources. 3. ROAD SENSOR SOLUTIONS One of the major steps of this research is the evaluation of the response and performance of the WIM sensors available on the market, in the laboratory, and on site, under controlled test conditions. This should allow to improve the algorithms used for the treatment of the sensor signals, and also to select the signals giving results which accuracy respects the tolerances required for direct enforcement. Sections 3.1 and 3.2 present the first tests performed at IFSTTAR Nantes, in the laboratory, and on the IFSSTAR accelerated pavement testing facility. 3.1. Laboratory assessment of WIM sensors A first evaluation of the electro-mechanical response of the WIM sensors has been carried out in the laboratory. Two types of sensor (piezo-quartz and piezo-ceramic) have been submitted to cyclic loading tests, using a hydraulic testing machine. Two types of tests have been performed: vertical loading tests, with the sensor resting on a rigid support, and 3 point bending tests. Figure 2 presents sectional views of the two types of sensors, as installed in the pavement. Figure 3 shows the test set up used for the 3-point bending tests on the piezo-quartz sensor. The piezo-ceramic sensor, which has a low stiffness, was placed on a metallic support beam, to carry out the 3-point bending tests. These tests have been used to determine the sensitivity of the sensors to the longitudinal position of the applied vertical load, and the influence of the conditions of support of the sensor. The results have shown that:
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Figure 2 – Sectional views of the piezo-quartz et piezo-ceramic sensors, after installation in a pavement
Figure 3 - Test set-up for the 3 point bending tests -
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The sensitivity of the sensors varies longitudinally, depending on the point of application of the vertical load. This variation represents about 1.7 % for the piezoquartz sensor, and 5.4 % for the piezo-ceramic sensor. The response of the piezo-quartz sensor is almost insensitive to the position of the support points and to the loading frequency. By its design, this sensor is sensitive only to the vertical stress applied to its upper side. In contrast, the response of the piezoceramic sensor depends on the curvature of the transducer, and on the loading frequency. In a pavement, the response of this sensor will be influenced by the lateral position of the wheels, the speed of the vehicles and the level of deflection of the pavement. These factors will have to be taken into account to improve the accuracy of this sensor
3.2. Experiment on the IFSTTAR full scale accelerated testing facility The fatigue test track of IFSTTAR Nantes is a full scale facility, designed to study damage of real pavements, under accelerated heavy traffic (Figure 4). This equipment offers unique characteristics, due to its large dimensions (120 m in length circular test track), to the loading speed, up to 100 km/h, and to the maximum load level (65 kN per wheel). The experiment was carried out on a thick bituminous pavement consisting of a 7 cm thick asphalt concrete wearing course, over 34 cm of asphalt road base, resting on a granular sub base. The deflection level meets the requirements of the class 1 (Excellent site) of the European specifications for WIM by COST 323 [3]. -5-
Figure 4 - The fatigue test track of IFSTTAR Nantes Ten WIM sensors, including piezo-ceramic sensors, two types of piezo-quartz sensors, and piezo-polymer sensors have been evaluated on the fatigue test track. Figures 5 and 6 show the different sensor positions on the test track. 25
Boucles magnétiques 20 Piezo-polymère
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0 -25
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Figure 5 - Positions of the WIM sensors on the fatigue test track
Figure 6 – View of the WIM sensors installed on the test track -6-
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The experiment involved: - the 10 WIM sensors previously described, - vertical displacement transducers and temperature sensors placed in the pavement, - 8 accelerometers installed on the 4 arms of the traffic simulator, to measure the dynamic load variations. Three different data acquisition systems have been used in parallel to record the different measurements: 2 ground based systems, and one on-board system installed on the traffic simulator, for the accelerometer measurements. To synchronize these 3 systems, four detection cells have been placed on the four arms of the traffic simulator, to measure precisely the time of passage of the loads on the WIM sensors. The tests have been carried out in 3 phases: (1) a first phase with the 4 arms equipped with single wheels, loaded at 45 kN. (2) a second phase, also with single wheels, but with variable loads (45 kN and 55 kN) and variable tire pressures (7, 8.5 and 9 bars). (3) a third phase, where the 4 arms of the traffic simulator have been equipped with different wheel configurations: single wheel, dual wheels, tandem, tridem. During each phase, different series of measurements have been performed, to evaluate the influence of the loading speed, of the transversal position of the wheels and of the temperature (by making measurements at different hours of the day). All these measurements have been stored in a data base of more than 30,000 WIM sensor signals, corresponding to 300 different measurement conditions. Figure 7 shows examples of response of WIM sensors obtained on the test track, under tandem wheel loading. For the piezo-quartz sensor (Figure 7a), the signal returns to zero very quickly after the passage of each wheel, indicating that the sensor is very little sensitive to the vertical deflection of the pavement. For the piezo-ceramic sensor (figure 7b), a signal is measured well before the wheel comes into contact with the sensor, and the return to zero is also much more progressive, indicating a much greater sensitivity to the deflection of the pavement, which makes the analysis of the measurements more complex.. 7a)Piezo-quartz sensor tandem axle load
7b) piezo-ceramic sensor tandem axle load
Figure 7 - Signals of WIM sensors under the passage of tandem axles The analysis of the results of this experiment is still in progress, but several conclusions can already be drawn: -7-
- the repeatability of the measurements of the different types of transducers, determined for several passages of the same load, under identical conditions, varies between 1% and 2%, and is independent on the type of wheel load; - the piezo-quartz sensors are, by their design, very little sensitive to pavement deformations, contrary to the other types of sensors. The variation of the measurements with the lateral position of the wheels is of the order of 10% to 15% for the piezo-quartz and piezo-ceramic sensors, and reaches 35% for the piezo-polymer sensors. A detailed analysis of the dynamic load variations remains to be done, in order to evaluate the accuracy of the WIM sensors, and the part of the variability of the measurements due to dynamic wheel load variations, and those due to the interaction between the sensor and the pavement. Finally, the response of the piezo-polymer sensors is strongly affected by temperature variations. The difference between two series of measurements, with the same loading conditions, performed in the morning and in the afternoon (with a variation of the surface temperature of about 20°C) can reach up to 60%. The remaining part of the work concerns the analysis of the dynamic load variations of the fatigue test track, principally based on the accelerometer measurements. The objective is to determine accurately the values of the applied loads when the wheels pass on each sensor, and thus to evaluate the accuracy of the measurements of the different sensors. On the basis of these results, suggestions will be made to improve the treatment of the sensor signals, and to optimize the accuracy of the measurements. Table 1 - Relative variation (coefficient of variation σ/m) of sensor measurements under the passage of a single wheel, at different speeds Sensor type Piezo-quartz type F Piezo-quartz type G Piezo-céramic Piezo-polymer
Velocity (km/h) 50.4 1.32 % 1.38 % 1.44 % 1.96 %
32.4 1.21 % 1.12 % 1.30 % 1.57 %
72 1.79 % 1.28 % 1.50 % 2.21 %
3. 3. Fibre optic sensor The use of fibre optic sensors in WIM systems presents many advantages: small sizes, sensibility of fibre optics to physical phenomena in the host medium, immunity to electromagnetic waves interference enabling their deployment in areas where the electronic sensors do not work, finally the electronics for the detection and data processing is simple, compared to the different conventional sensors [4]. Different configurations have been used to realize WIM systems based on fibre optics: amplitude variations of optical signal due to the attenuation caused by the pressure on the optical fibre deformation, measurement using Bragg gratings sensors installed into the pavement [5], or the phase variation of optical wave in the fibre optic sensor [6]. A polarimetric sensor based on the measurement of phase shift between two orthogonal polarizations in the optical fibre has been developed in the project WAVE [7]. The birefringence has been created in the fibre using an external pressure, but the sensitivity to the temperature variations has limited its performance [8].
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Research work is carried out on the realization of a polarimetric sensor with low sensitivity to temperature. The first step was to find and analyse the behaviour of birefringent optical fibre, with low sensitivity to temperature. Figure 6 shows the birefringence variations of different birefringent optical fibres as a function of the temperature. An optical fibre with elliptical core has the smallest birefringence depends on the temperature variations.
Figure 6 - Variation of birefringence as a function of the temperature for 1m sensor length. Currently the realization of the optical set-up is in progress and laboratory tests will validate the choice of the optical fibre. The interrogation technique is in development to obtain a high performance system. 4. BRIDGE WEIGH-IN-MOTION AS MEANS 4.1. State of the art Bridge weigh-in-motion (also called B-WIM) uses the deck of a bridge as a scale in order to assess the weights of the axles and the vehicles. This idea has first been proposed by F. Moses in the late 1970s [9]. In this work, the difference between the recorded stress on a bridge and the calculated ones obtained by convolution of the influence line and the axle weights is minimized with the least squares method. The axle weights are therefore assessed while assuming that the speed of the vehicles are known (measured by sensors embedded in the road). In the frame of the WAVE project a more efficient algorithm has been developed, still based on the least squares but with a global optimization method. It makes it possible to assess at once the speeds, the distances between vehicles and the axle weights [10, 11]. Later, algorithms have been proposed to take into account the lateral position of the loads on the deck of the bridge [12], using influence surfaces. This makes it possible to apply this concept to bridges where the lateral behaviour is not uniform or linear (for example, girder bridges and bridges with orthotropic decks). Recent research works are focused on the accuracy improvement introducing wavelet analysis, use of the entropy of the system or regularization of the signals [13]. 4.2. Improvement of existing systems IFSTTAR uses since 2005 the SiWIM system developed by the Slovenian company CESTELS. It has been tested on integral bridges and on two steel structures with orthotropic deck (Autreville viaduct and Millau viaduct). For integral bridges, the influence of pavement roughness, and of the slope and the bias of the bridge have been shown. -9-
Tests in operational conditions have been undertaken on an integral bridge of highway A9, at Saint-Jean-de-Vedas near Montpellier (Figure 7).
Figure 7 - Integral bridge instrumented on highway A9 for B-WIM The SiWIM accuracy has been assessed through comparison with a static scale, approved for enforcement, located at a weighing station on the same highway a few kilometres further. Precision class B(10) has been reached (Table 2). Tableau 2 - Accuracy of the bridge weigh-in-motion on a integral bridge on highway A9
GVW Group of axles Single axles Axles in groups
x0
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In the frame of the project AOC, work is focused on the improvement and making reliable the recorded on integral bridges signal processing, in order to eliminate measure out of the tolerance for enforcement (sorting of the vehicles), and on the research of a better adapted algorithm for bridges for orthotropic steel decks, or even other types of structures. An instrumentation campaign is foreseen on an integral bridge on highway A1 near Senlis in the North of Paris, in order to validate the coupling of the SiWIM system with a video camera for identification of the overloaded trucks, and in order to test the first algorithms for sorting. 5. TESTING AND TYPE APPROVAL 5.1. Objectives, test plan and trial site The road tests aim at validating by a series of tests in controlled current traffic situations, the metrological and functional feasibility of an AOC by WIM. There are two main steps: (1) to demonstrate the technical and metrological feasibility of the measuring instrument. The measures provided by the WIM systems selected for the AOC should meet the requirements expressed in the chapter I, -10-
(2) to demonstrate the equipment functionality by constructing one or more prototypes of WIM system integrating all AOC functions. A detailed test plan of the road trials and on an open site was written by IFSTTAR and Cerema, in collaboration with the vendors/suppliers participating in the project. It resumed the objectives and organization of the trials, and it outlines the assessment methodology and the presentation of the results. It is based on the background documents: - Méthodologie d'évaluation de nouveaux capteurs de trafic routier (CERTU, 2002); - European specifications (pre-standard) COST323 [3]; - recommandation OIML R134-1 [2]; - French standard NF X06-032 : Traitement statistique des données. Détermination d'un intervalle statistique de dispersion, used as a frame of the data statistical analysis. The chosen trial site is located on the RN4, a 2x2 lanes highway, near the interchange of Maulan towards Nancy to Paris, between the towns of Ligny-en-Barrois and Saint-Dizier (Figure 8). This route is highly trafficked by HGVs and is equipped with a high speed WIM equipment (HS WIM-E) for screening of presumed overloaded vehicles upstream of a control area fitted with an approval low-speed WIM system (LS WIM-E).
Figure 8 – Screening site (Maulan, right) and control site (Rupt-aux-Nonains, left) 5.2. Companies partnership A call for participation have been launched inviting companies involved in WIM, including ISWIM members, to participate to the project, including laboratory tests, accelerated pavement testing facility test and on road trials. Sterela and Fareco (France) joined the project as early as mid-2014 and proposed sensors (piezo-quartz by Sterela and piezoceramic by Fareco) to three types of trials. TDC (UK) and Intercomp (USA) have expressed an interest, above all for the road test, the first company with piezo-polymer sensors and the second company with its own sensor. IRD (Canada) has expressed interest without however confirming its participation to date. Cross Zlín (Czech Republic) was interested but finally declined. Companies marketing mature enough products and technologies to be assessed, and improved if needed, to meet the requirements of the AOC are eligible as project partners. In this case they provide the hardware, software and knowledge required for studies and research related to the tests. Each company installs, calibrates and maintains its devices for the duration of the trial, complying with the specifications of the road site operator and the project managers. It provides to IFSTTAR and Cerema all measurements produced by its device (raw and elaborated) during all measures periods and shall communicate all information useful for the implementation of these hardware and software. IFSTTAR and Cerema will keep confidential all information property of the partners and will not -11-
communicate to third party the raw data gathered by each system. Static or low-speed weighing reference will be provided to partners for all vehicles weighed by their system. IFSTTAR and Cerema will give a feedback to each partner with regard to their own system. They could support improving their systems for the purpose AOC. The partners undertake to carry out the changes and updates, including software (data processing), proposed by or jointly defined with IFSTTAR and Cerema provided that they are compatible with the system and the means available. 5.3 Certification, type approval, initial and in-service verifications One of the key challenges of the project is to develop certification and type approval procedures of WIM systems, adapted to the AOC. The statistical approach proposed in the European specification of WIM COST323 cannot be used for such a legal purpose, as stated in its scope. 100% of the measured vehicles presumed as overloaded and screened by the system must be with the metrological tolerances, i.e. ±5% for the gross vehicle weight, and 8 to 10% (to be defined) for the axle load. The OIML R134 recommendation will be used. However, it is not required that 100% of the checked vehicles are within these tolerances. The empty of partly loaded vehicles may be ignored as they comply with the legal limits. The fully loaded and overloaded vehicles are those targeted, and the scattering and errors of measurements are lower with these vehicles, because of less dynamics (vertical acceleration) and because part of the WIM system error is not proportional to the load. Moreover, to be approved by the legal metrology, the system should not provide any measure outside the MPE (maximum permitted error), and therefore should double check and either correct or eliminates doubtful or uncertain measurements, using any relevant criteria to be developed in this project. The criteria may be based on an analysis of the dynamic behaviour of the vehicle, e.g. identifying large variations of the vertical acceleration and tyre forces, or runs out of the lateral tolerance of the weighing sensor, or even by an in-depth analysis of the raw signal delivered by the sensor compared to a database of reference signals, such as those recorded on the large testing facility in Nantes (section 3.2). The choice of the relevant sensors and system design and architecture will depend on the ability to comply with these requirements. Simulators and models of heavy vehicles will be used to carry out digital simulations and to check these procedures. The certification and type approval procedure should include this sorting algorithm and its efficiency, and ensure that the wrong detection rate is below an acceptable threshold. The type approval test should both check the main parts of the WIM system, WIM sensors, electronics, software, in various environmental conditions, and then the whole system must be tested on a reference test site, with excellent geometrical and mechanical characteristics, e.g. a class 1 WIM site according to the European specification COST323. For the type approval test, the test plan shall be exhaustive and representative of all the potential traffic conditions, taking into account all the influencing factors, e.g. suspension type, tyre, axles, braking, accelerations, velocity, etc. Then each WIM system shall be tested after its installation or any major repair or modification, with half the tolerances through an initial verification. The system in operation shall be periodically tested (e.g. once a year) with the full tolerances through in-service verification. The test plan of the initial and in-service verification shall be lighter than for the type approval, and manageable/affordable for the users.
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The case of B-WIM systems will require a particular attention because until now none of these systems passed type approval and legal verifications. Until now these systems are only used for statistical purposes, traffic monitoring, infrastructure assessment and overload screening. There are all qualified against the COST323 specifications, or similar statistical specifications. The definition of the “instrument” will not be the easiest task. 6. CONCLUSIONS ET PERSPECTIVES The AOC by WIM is a very challenging objective and requires a series of significant steps forwards and progresses, both in WIM technology and in its implementation, operation and certification. This project mainly addresses the technological and scientific issues, but also, as a central issue, the metrological aspects of certification and type approval. To demonstrate the feasibility of AOC by WIM, IFSTTAR decided to re-analyse the whole chain of measurement, from the sensors tested in fully controlled conditions in laboratory and on a large testing facility, to the whole system including electronics and software on real road test sites. Among the key issues to be resolved, the criteria and algorithm sorting the presumed overloaded vehicles weighed within the required tolerances is a major technological barrier. The detailed and partly redundant information provided either by MSWIM or B-WIM systems may be used for this purpose. It will not be critical if the first AOC WIM systems only catch 10, 20, 30 or 50% of the overloaded vehicles, i.e. if the missed detection rate is rather high, because in any cases it will be much more efficient than any human based control. And this rate may increase later on, with further developments and improvements. But the wrong detection rate must remain negligible in order to avoid penalizing legally loaded vehicles. Any mistake of that type could quickly kill the whole procedure and system. A strong partnership with WIM manufacturers and vendors is implemented in this project as the companies already developed their own know-how and have a great field experience. Combining their technology and the scientific R&D efforts of IFSTTAR and Cerema, we hope to successfully address this great challenge, and contribute to a better compliance of heavy commercial vehicles weights and dimensions in the future. International exchanges through ISWIM (international Society for WIM) and European cooperation are also envisaged as a factor to speed up the R&D process and to get harmonized procedures and standards. AOC may be beneficial for the society, the economy, the road safety, the infrastructure and to ensure a fair competition in an open market. AKNOWLEDGEMENT Authors express their thanks to the DGITM (General Directorate for Infrastructure, Transports and Sea) of the French Ministry of Ecology, Sustainable Development and Energy), for supporting this project, to the public road operators (DIR) and to the DREAL traffic officers for installing and operating WIM systems and performing controls. All the AOC project participants are acknowledged for their contribution: M. Bouteldja (Cerema), A. Khadour, J-M. Piau and J-M. Simonin (IFSTTAR), and G. Otto (FAPEU, Brazil/Ifsttar).
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REFERENCES 1. Dolcemascolo, V., Hornych, P., Jacob, B., Schmidt, F., Klein, E. (2015). Surveillance du trafic routier de poids lourds et des surcharges en France et applications. Soumis au 25e congrès mondial de la route, AIPCR, Seoul, 2-6 novembre. 2. OIML (2006). Automatic Instruments for weighing Road Vehicles in Motion and Axle Load measuring. Part 1: Metrological and technical requirements – Tests. R 134-1. 3. Jacob, B., O’Brien, E.J. and Jehaes, S. (2002). Weigh-in-Motion of Road Vehicles - Final Report of the COST323 Action. LCPC, Paris, 538 pp., + French edition (2004). 4. Fang, Z., Chin, K.K., Qu, R. and Cai, H. (2012). Fiber Sensitivities and Fiber Devices. In Fundamentals of Optical Fiber Sensors, ed. John Wiley & Sons, Inc. 5. Tosi, D., Olivero, M., Vallan, A. and Perrone, G. (2010). Weigh-in-motion through fibre Bragg grating optical sensors. Electronics Letters, vol.46, no.17, pp.1223-1225. 6. Verbandt, Y., Verwilghen, B., Cloetens, P., Kempen, L., Thienpont, H., Veretennicoff, I., Vinckenroy, G., Wilde, W.P. and Voet, M.H. (1997). Polarimetric optical fiber sensors: aspects of sensitivity and practical implementation. Optical Review, vol. 4, pp. A75-A79. 7. Barbachi, M. and Caussignac, J.M. (1996). Development of a single-mode optical fibre sensor for civil engineering applications. Proc. SPIE 2718, 398-407. 8. Lesnik, D. and Donlagic, D. (2013). In-line, fiber-optic polarimetric twist/torsion sensor. Optics Letters, vol. 38, pp. 1494-1496. 9. Moses, F. and Ghosn, M. (1983). Instrumentation for Weighing Trucks-in-Motion for Highway Bridge Loads. Final report FHWA/OH-83/001, August. 10. Jacob, B. (1999). Proceedings of the Final Symposium of the project WAVE (1996-99). Paris, May 6-7, Hermes Science Publications, Paris, 352 pp. 11. Jacob, B. (2002). Weigh-in-motion of Axles and Vehicles for Europe. Final Report of the Project WAVE, LCPC, Paris, 103 pp. 12. Quilligan, M. (2003). Bridge Weigh-in-Motion, Development of a 2-D Multi-Vehicle Algorithm. Licentiate Thesis, Royal Institute of Technology, Sweden. 13. O’Brien, E.J., Rowley, C., Gonzalez, A. et al. (2009). A regularized solution to the Bridge Weigh-in-Motion equations. International Journal of Heavy Vehicles, 16(3), 310-327.
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