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For decades, remote sensing technologies and the non-destructive testing (NDT) methods have been used for the assessment of transport infrastructure, highways, railways and airfields. The existence of provisions of multi-source, multi-scale and multi-temporal based information on infrastructure conditions on one hand and the developments of hardware and software technologies in the other, have provided opportunities for the growth of the applications of NDT techniques. The outcome lends itself to be incorporated into existing infrastructure management models. This paper presents an overview of the latest developments in ground-based (Ground Penetrating Radar (GPR) and interferometric radar systems) and satellite (space-borne Synthetic Aperture Radar (SAR) interferometry) remote sensing that applied to transport infrastructures. The applications of GPR to pavements, e.g. multi-layered pavement structure and asphalt concrete (AC) density, and rail-tracks, e.g. ballast assessment are discussed. In addition, the applicability of ground-based radar interferometry and SAR for the bridge structural health monitoring and horizontal transport infrastructure is presented. A novel integrated approach is introduced to form the base of a novel intelligent transport infrastructure management system. The approach is aimed utilizing the structure condition assessment-based information collected using SAR and NDT techniques to prioritize maintenance/rehabilitation activities of transportation assets. For example, analyses of multi-temporal SAR data are used to identify areas of concern at the network level (e.g. differential settlements at bridge approaches or rail track-beds, and excessive deformation rate of pavement surface). The identified locations would be further assessed using ground-based techniques to collect more accurate data. This approach would provide an effective, efficient, and sustainable state of good repair over the life cycle of the transportation infrastructure system.

In recent years, successful applications of the Synthetic Aperture Radar Interferometry (InSAR) have been reported for the monitoring of subsidence and deformation in transport infrastructures. Compared to other non-destructive surveying methodologies, this technique can perform network-level analyses more rapidly and it can provide time-series of ground displacements by multi-temporal data acquisition. However, processing of satellite images by high-resolution sensors (i.e., X-band radars) is demanding in terms of computational resources and specialist skills. This aspect has contributed to partially hinder this technique to become a strategic infrastructure asset management tool. Parallel to this, it is important to emphasise that the use of middle-range frequency SAR sensors (i.e., C-band) allows for the acquisition of lighter datasets and, hence, more computationally affordable analyses. However, due to a lower system resolution and the challenges in identifying features of scattering objects with size below the resolution cell, the C-band imagery is usually not employed for infrastructure monitoring. This limitation could be compensated in rural environment areas, where transport infrastructures are usually the most stable scatterers.\ud This study aims to demonstrate the viability of the medium-range resolution SAR imagery in transport asset monitoring for the preliminary identification of sections affected by subsidence in rural areas. InSAR analyses of high (COSMO-SkyMed) and medium-resolution (Sentinel-1A) datasets are performed on a dual-carriageway rural motorway. A comparison between the Persistent Scatterers Interferometry (PSI) outcomes from data processed with the two resolutions demonstrates the viability of using Sentinel-1A images for multi-temporal subsidence monitoring in highway infrastructure.

El presente artículo integra la línea de investigación que se viene desarrollando desde el Centro de Estudios de Innovación Institucional (CEII-UNCuyo/CONICET), a partir de los enfoques del análisis de políticas públicas, la participación ciudadana y el desarrollo territorial. Se parte de la afirmación de que la participación tiene un rol ineludible en los procesos de desarrollo. En consecuencia, el objetivo del trabajo es reflexionar críticamente sobre cuáles deberían ser las dimensiones de un instrumento orientado a evaluar las prácticas participativas implementadas en procesos de políticas, principalmente las orientadas al desarrollo del territorio. En trabajos anteriores, se avanzó en la definición de un conjunto de dimensiones y criterios que permitieron analizar y evaluar cómo se diseñan, implementan y evalúan los mecanismos de participación ciudadana, así como también la forma en que se trabajan los aportes de política que surgen de los mismos, fundamentalmente en la escala subnacional y local de gobierno. El análisis comparado de diversos casos de América Latina y el Caribe arrojó resultados preliminares que dan origen a la preocupación actual por continuar discutiendo los alcances y limitaciones de las dimensiones y criterios necesarios para evaluar la forma en la que la ciudadanía se hace parte de la gestión de las cuestiones públicas. This article integrates the line of research being developed by the Center for the Study of Institutional Innovation (CEII-UNCuyo/ CONICET), based on the approaches of public policy analysis, citizen participation and territorial development. It is based on the assertion that participation has an unavoidable role in development processes. Consequently, the objective of the work is to critically reflect on what should be the dimensions of an instrument aimed at evaluating participatory practices implemented in policy processes. Mainly, those oriented to territorial development. In previous works, progress was made in the definition of a set of dimensions and criteria that made it possible to analyze and evaluate how citizen participation mechanisms are designed, implemented and evaluated. As well as the way in which the policy contributions that arise from them are worked, fundamentally at the subnational and local governmental scale. The comparative analysis of various cases in Latin America and the Caribbean yielded preliminary results that give rise to the current concern to continue discussing the scope and limitations of the dimensions and criteria needed to evaluate the way in which citizens participate in the management of public issues. Fil: Guardamagna, Melina. Consejo Nacional de Investigaciones Científicas y Técnicas. Universidad Nacional de Cuyo; Argentina. Fil: Benedetto, Andrea. Universidad Nacional de Cuyo; Argentina.

Multi-temporal Interferometric Synthetic Aperture Radar (InSAR) is a space-borne monitoring technique capable of detecting cumulative surface displacements with millimeter accuracy in the Line of Sight (LOS) of the radar sensor [1-3]. Several developments in the processing methods and\ud the increasing availability of SAR datasets from different satellite missions, have proven the viability of this technique in the near-real-time assessment of bridges and the health monitoring of transport infrastructures [2-4].\ud This research aims to demonstrate the potential of satellite-based remote sensing techniques as an innovative health-monitoring method for structural assessment of bridges and the prevention of damages by structural subsidence, using high-resolution SAR datasets integrated with\ud complementary Ground-Based (GB) Non-Destructive Testing (NDT) techniques. To this purpose, high-resolution COSMO‐SkyMed (CSK) products provided by the Italian Space Agency (ASI) were acquired and processed.\ud In particular, a multi-temporal InSAR analysis was developed to identify and monitor the structural displacements of the Rochester Bridge, located in Rochester, Kent, UK. To this extent, a clustering operation is realised to collect the identified Persistent Scatterers (PSs) over the structural elements of the bridge (i.e., bridge piers and arcs). Furthermore, several sub-clusters with a comparable deformation trend were identified and located over the bridge elements. This operation paves the way for an automatisation of the process through a Machine Learning (ML) clustering algorithms to assign each PS data-point to specific groups, based on the structural element type and the trend of seasonal deformation time-series.\ud The outcomes of this study demonstrate how multi-temporal InSAR remote sensing techniques can be synergistically applied to complement non-destructive ground-based analyses, paving the way for future integrated methodologies in the monitoring of infrastructure assets.

A wide range of engineering and geoscience applications today rely on the extensive employment of specialist non-destructive testing (NDT) methods. The standalone use of these techniques has become established in many areas given the research progress achieved in the use of electrical, electromagnetic, optical and acoustic NDT methods. The capabilities and potential of these methods have been comprehensively explored and assessed, bringing research up to date. Research efforts have been mostly focussed on achieving new theoretical developments, the advancement of hardware and software components, and on finding new surveying and data processing methods and interpretations. As a result of this, the standard of quality is excellent, and data can be collected very accurately with available technology.\ud At the same time, the concept of integration between sensing methodologies, in terms of modelling data of different scale domains and resolutions, is becoming a real challenge within the scientific community, and is starting to be recognised as a key research area that could drastically enhance the capabilities of existing NDT technology when faced with new and complex scenarios. This trend is driven by an increase in the demand for more effective solutions for the investigation of non-conventional scenarios. These investigations need to be carried out while maintaining reasonable costs and within feasible time requirements, as multiple methods and equipment and interdisciplinary expertise are involved.

This paper presents a computer-aided multi-stage methodology for the simulation of railway ballasts using the Random Sequential Adsorption (RSA – 2D domain) paradigm. The primary stage in this endeavour is the numerical generation of a synthetic sample by a "particle sizing and positioning" process followed by a "compaction" process. The synthetic samples of ballast are then visualised in the Computer-Aided Design (CAD) environment. The outcomes of the simulation are analysed by comparison with the results of an experimental investigation carried out using a methacrylate container in which real samples of railway ballast are formed. A test of model reliability is carried out between the aggregates number and the grading curves of the synthetic sample and the real one. A validation is therefore performed using the ground-penetrating radar (GPR) non-destructive testing (NDT) method and the finite-difference time-domain (FDTD) simulation developed in a computer-aided environment. The results prove the viability and the applicability of the proposed modelling for the assessment of railway ballast conditions.

El trabajo se centra en el análisis de las trayectorias ocupacionales inter-generacionales de familias que residen en zonas urbanas de Mendoza. Dado que estas trayectorias se explican por cambios en la estructura social, se incluyen indicadores relativos a los efectos del proceso de industrialización, la transformación neoliberal iniciada en 1976 y la recomposición que arranca en 2001. Para una aproximación al análisis de la movilidad social, se aplica el método biográfico. Mediante entrevistas en profundidad se reconstruyen árboles genealógicos de familias y se examina la permanencia o cambio en términos de la posición social, a lo largo de tres generaciones. Fil: Yañez, Lilibeth. Universidad Nacional de Cuyo. Facultad de Ciencias Políticas y Sociales Fil: Lecaro, Patricia. Universidad Nacional de Cuyo. Facultad de Ciencias Políticas y Sociales Fil: Bustos, Rosa María. Universidad Nacional de Cuyo. Facultad de Ciencias Políticas y Sociales Fil: Benedetto, Andrea. Universidad Nacional de Cuyo. Facultad de Ciencias Políticas y Sociales Fil: Gusman, Natalia. Universidad Nacional de Cuyo. Facultad de Ciencias Políticas y Sociales Fil: Yazlli, Julieta. Universidad Nacional de Cuyo. Facultad de Ciencias Políticas y Sociales Fil: Yazlli, Bernardo. Universidad Nacional de Cuyo. Facultad de Ciencias Políticas y Sociales Fil: Staller, Ivan . Universidad Nacional de Cuyo. Facultad de Ciencias Políticas y Sociales Fil: González, Miguel. Universidad Nacional de Cuyo. Facultad de Ciencias Políticas y Sociales Fil: Estrada, Marina. Universidad Nacional de Cuyo. Facultad de Ciencias Políticas y Sociales Fil: Pereira, Natalia. Universidad Nacional de Cuyo. Facultad de Ciencias Políticas y Sociales Fil: García, Sayi. Universidad Nacional de Cuyo. Facultad de Ciencias Políticas y Sociales Fil: Salomón, Malen. Universidad Nacional de Cuyo. Facultad de Ciencias Políticas y Sociales

This study deals with a case report about the planning and the performance of GPR surveys carried out in the town of Amatrice, in the district of Rieti, Italy.\ud As sadly known, the town has been hit by a 6.9 magnitude earthquake in the nighttime of August 24th 2016. The strength of the seism, along with the age and the deterioration rate of the structural asset, have caused the razing to the ground and the critical damaging of the majority of the buildings within the “red zone area”, corresponding to the historical town center.\ud In the early recovery phase taking place afterwards, the strong seismic swarm subsequent the main shake has sensitively slowed down the rescue and rehabilitation operations. Moreover, the main issue was related to the unsafety operational conditions of volunteers and firemen. To this effect, the geotechnical stability of the roads and the large operational areas represented critical issues, as up to 40 tons crane trucks were needed to put in safety the highest buildings, such as three-floor buildings and historical towers.\ud In this framework, ground-penetrating radar (GPR) provided a valuable help in preliminary assessing the stability of the areas where the crane trucks were planned to operate as well as to be parked over. The main objective of the GPR tests was to verify the absence of possible cavities beneath the ground surface that could undermine the strength of the surface under heavy loadings. To that effect, a multi-frequency ground-coupled GPR system was used. This radar system can simultaneously collect data at both the frequencies of 600 MHz and 1600 MHz. Four different sites were surveyed, namely, two sections of the main road passed on by the cranes, and two machinery depot areas down by the towers. In the former case, the surveys were performed by parallel longitudinal scans, due to the significant longitudinal length of the sections, whereas in the latter, two grids with differing sizes were realized and scanned for producing horizontal tomographic maps.\ud In both the cases, useful insights have been pointed out, and relevant critical areas of possible weaknesses in the soil strength, where to focus further and more specialist analyses, have been detected. It is important to emphasize on the details provided about the working procedures in such a complex environment.

The need for effective and efficient railway maintenance is always more demanded all over the world as the main consequence of aging and degradation of infrastructures. Primarily, the filling of air voids within a railway ballast track-bed by fine-grained materials, coming up from the subballast layers by vibrations and capillarity effects, can heavily affect both the bearing and the draining capacity of the infrastructure with major impacts on safety. This occurrence is typically referred to as “fouling”. When ballast is fouled, especially by clay, its internal friction angle is undermined, with serious lowering of the strength properties and increase of deformation rates of the whole rail track-bed. Thereby, a detailed and up-to-date knowledge of the quality of the railway substructure is mandatory for scheduling proper maintenance, with the final goal of optimizing the productivity while keeping the safety at the highest standard. This paper aims at reviewing a set of maintenance methodologies, spanning from the traditional and most employed ones, up to the most innovative approaches available in the market, with a special focus on the Ground Penetrating Radar (GPR) non-destructive testing (NDT) technique. The breakthrough brought by the application of new processing approaches is also analyzed and a methodological framework is given on some of the most recent and effective maintenance practices.

The present work focuses on the application of the Ground-Penetrating Radar (GPR) technique on a flexible pavement structure for the assessment of the layer dielectrics. Two air-coupled GPR systems, with antennas operating at 1 GHz and 2 GHz central frequencies were used for testing and simulation purposes. The effectiveness of the combination of i) the Finite-Difference Time-Domain (FDTD) technique for the simulation of the GPR signal, and ii) the GPR reflection amplitude technique, for the estimation of the dielectrics of the pavement layers, was analyzed. Three steps of processing were proposed and the results compared each to one another. In the first stage, the signal was simulated using design project data for the investigated cross-section and dielectric permittivity values for the (design) construction materials, derived from the literature. In the second stage, the dielectrics were computed by the signal collected within a real-life flexible pavement. Both the two-way travel time and the reflection amplitude techniques were performed. The third step was focused on analyzing the accuracy of the reflection amplitude method combined with the optimized simulation of the GPR signal. The results demonstrated good potential on the use of the proposed approach with respect to the application of the reflection amplitude technique for the assessment of the pavement layer dielectrics.

The first step in the planning for a renewal of a railway network consists in gathering information, as effectively as possible, about the state of the railway tracks. Nowadays, this activity is mostly carried out by digging trenches at regular intervals along the whole network, to evaluate both geometrical and geotechnical properties of the railway track bed. This involves issues, mainly concerning the invasiveness of the operations, the impacts on the rail traffic, the high costs, and the low levels of significance concerning such discrete data set. Ground-penetrating radar (GPR) can represent a useful technique for overstepping these issues, as it can be directly mounted onto a train crossing the railway, and collect continuous information along the network. This study is aimed at defining an empirical model for the prediction of fouling in railway ballast, by using GPR. With this purpose, a thorough laboratory campaign was implemented within the facilities of Roma Tre University. In more details, a 1.47 m long × 1.47 m wide × 0.48 m height plexiglass framework, accounting for the domain of investigation, was laid over a perfect electric conductor, and filled up with several configuration of railway ballast and fouling material (clayey sand), thereby representing different levels of fouling. Then, the set of fouling configurations was surveyed with several GPR systems. In particular, a ground-coupled multi-channel radar (600 MHz and 1600 MHz center frequency antennas) and three air-launched radar systems (1000 MHz and 2000 MHz center frequency antennas) were employed for surveying the materials. By observing the results both in terms of time and frequency domains, interesting insights are highlighted and an empirical model, relating in particular the shape of the frequency spectrum of the signal and the percentage of fouling characterizing the surveyed material, is finally proposed. \ud Acknowledgement The Authors thank COST, for funding the Action TU1208 "Civil Engineering Applications of Ground Penetrating Radar."

This work aims at presenting the main results achieved by Working Group (WG) 1 "Novel Ground Penetrating Radar instrumentation" of the COST (European COoperation in Science and Technology) Action TU1208 "Civil Engineering Applications of Ground Penetrating Radar" (www.cost.eu, www.GPRadar.eu). \ud \ud The principal goal of the Action, which started in April 2013 and is ending in October 2017, is to exchange and increase scientific-technical knowledge and experience of Ground Penetrating Radar techniques in civil engineering, whilst promoting throughout Europe the effective use of this safe non-destructive technique. The Action involves more than 300 Members from 28 COST Countries, a Cooperating State, 6 Near Neighbour Countries and 6 International Partner Countries.

The sensibility towards environmental issues along with the attention on preserving natural heritage, especially ancient trees and rare plants, has greatly increased, and the management and the control of the forestall heritage and the floral system has become accordingly a high-priority objective to achieve. One of the main factors of tree decay which originally gained public attention is the presence of unknown pathogens carried along by the wind, which can lead to epidemic phenomena and often to a quick death of entire forests. In such an emergency situation, two main approaches can be followed, namely, i) active measures (i.e. the avoidance of any contact between the pathogenic spores and the trees by using bio-security measures) and ii) passive measures (i.e. the application of policies for the control and the management of the forestall heritage aimed at identifying the early-stage symptoms of the disease). Since the latest approach is based on the monitoring of living trees, invasive methods of health assessment like cutting off branches or incremental coring are increasingly discouraged, and non-destructive evaluation proves to be the only option to undertake. The applications of non-destructive testing (NDT) techniques in forestry sciences are often self-standing and not integrated with one another. This is often due to a lack of knowledge from the NDT users towards the physics and the bio-chemical processes which mainly govern the life cycle of trees and plants. Such an issue is emphasized by the evident complexity of the plant and trunk systems themselves. Notwithstanding this, the ground-penetrating radar (GPR) technique has proved to be one of the most effective, due to its high versatility, rapidity in collecting data and the provision of reliable results at relatively limited costs. The use of GPR can provide invaluable information about the effective tree trunk assessment and appraisals, tree roots mapping, soil interaction with tree and plants. In addition, the use of simulation can be a supporting tool for the development of a clear understanding of the decay processes in trees.\ud In this study, a demonstration of the GPR potential in the health monitoring of an ancient tree has been given. The main objectives of the research were to provide an effective mapping of the tree roots as well as reliable simulation scenarios representing a variety of possible internal defects in terms of shape and formation. To these purposes, the soil around a 100-years old fir tree, with a trunk circumference of 3.40 m and an average radius of 0.55 m, was investigated. Nine radial scans, 0.30 m spaced each to one another, were carried out all around the tree circumference starting from 0.50 m the outer surface of the bark. A ground-coupled multi-frequency GPR system equipped with 600 MHz and 1600 MHz central frequency antennas was used for testing purposes. In order to reach the maximum penetration depth of the root system, only the 600 MHz frequency was considered for data processing purposes. After the application of a dedicated signal processing scheme, it was possible to produce a tomographic map of amplitudes covering a swept circle with an outer radius of 3.45 m and an inner radius of 1.05 m up to a maximum depth of 1.56 m. By using a set of specially developed algorithms it was possible to extract signal amplitude information reliably related to the position of the tree roots under the soil.\ud In addition to the above objective, finite-difference time-domain (FDTD) simulations of the electromagnetic field propagation through the cross section of a trunk were carried out. To this purpose, the numerical simulator package gprMax 2D was used. The freeware tool E2GPR aided the design of the gprMax models and their distributed execution on multicore machines. The dimensions and the dielectric properties of the simulated trunk were consistent with the investigated fir tree (actual data collected). Furthermore, a variety of defects representing cavities created due to decay was simulated. The results from the simulations demonstrated significant potential for the interpretation of complex decay phenomena within the trunk as well as for mapping and comparison of the actual field data.

The assessment of the underground construction details of a road infrastructure is a problem of great concern in highway engineering. The case becomes complicated especially when damages reoccur after carrying out remedial surface maintenance and repair works over the life cycle of the infrastructure. The challenge will be exacerbated at the presence of underground watercourses, such that the geotechnical stability of the entire road structure could be threatened.\ud In this respect, ground-penetrating radar (GPR) has been recognised and accepted as one of the most effective non-destructive testing (NDT) techniques that could be employed in identifying the cause/s of such problems. The recent advancements and developments made in the field of GPR hardware as well as the current level of understanding of the applications and processing techniques of the GPR data have immensely added to the reliability in the utilisation of this tool in variety of subsurface investigation projects.\ud In view of this, the work presented in here focuses on the assessment of the underground construction details of a road pavement using different frequency GPR antenna systems. In addition to this, the possible presence and location of an underground watercourse was investigated in this work. The existence of the latter problem was perceived due to reoccurrence of longitudinal and traversal road surface cracking as well as subsidence at a particular location of the road. Reoccurrence of this damage was interpreted and related to the possible existence of an underground watercourse. The original design and the construction of the road were as such to prevent this movement. Therefore it seemed necessary to perform a GPR survey to investigate and confirm the underground construction details of the road. To this purpose, the identified area was surveyed using high to low frequency antennas with 2000 MHz, 900 MHz, 600 MHz and 200 MHz central frequencies of investigation. Scans were performed at 1m intervals in the direction of the road started from the reference (first) transversal axis located 5m behind the drain at the side of the road.\ud The results obtained using the 2000 MHz antenna showed that the road construction consisted of an asphalt layer of 10 cm thickness overlaying a reinforced concrete block with two layers of rebar mesh. In addition, significant moisture damage and evidence of subsidence within the road were identified. The 900 MHz frequency antenna confirmed the above results as well as suggesting the existence of subsidence at the lower areas of the road foundation. Furthermore, results revealed the existence of an unidentified object at the deeper depth. This was not detected by the higher frequency antenna. The maximum depth of penetration was achieved by using the 600 MHz and the 200 MHz antennas (maximum of 3 m). To that effect this investigation did not identify or confirm the existence of any underground watercourse.

Ground-penetrating radar (GPR) is one of the most acknowledged and established non-destructive testing (NDT)\ud techniques within the context of the health monitoring and assessment of transportation infrastructures. GPR is being increasingly used for the effective management of infrastructural assets as it weakens the case for using other destructive monitoring methods, such as digging holes, and allows for rapid and reliable detection of many causes of the subsurface damage. Thereby, its usage favours the optimisation of the economical expenditure for the effective maintenance of great infrastructures as well as it improves the public safety by preventing or not raising the risk of accidents.\ud GPR has been used in highway, railway and airfield engineering as well as for the monitoring of critical infrastructures, such as bridges and tunnels. It has found established use in the assessment of the geometric properties of the subsurface, such as in the case of the evaluation of the pavement layer thicknesses, or the size of the rebars in concrete-made structural components. Major physical-based investigations have been focused on the evaluation of the moisture ingress in flexible road pavements and in concrete structures, as well as on the detection of the rebars corrosion caused by the ingress of chloride. The majority of these parameters are evaluated using methods of signal analysis and data processing based on the signal in the time domain.\ud The sophistication of the hardware and software of the GPR systems over the last few years as well as the recent advances achieved in the research have contributed to raise the high potential of this non-destructive technique and paved the way towards new application areas in transportation engineering. In particular, GPR is nowadays finding major application when used with complementary non-destructive testing techniques, although it has still proved to provide reliable results in various self-standing applications.\ud This work aims at presenting the recent advances and the new perspectives in the application of GPR to transportation engineering. This study reports on new experimental-based and theoretical models for the assessment of the physical (i.e. clay and water content in subgrade soils, railway ballast fouling) and the mechanical (i.e. the Young’s modulus of elasticity) properties that are critical in maintaining the structural stability and the bearing capacity of the major transport infrastructures, such as highways, railways and airfields.\ud With regard to the physical parameters, the electromagnetic behaviour related to the clay content in the loadbearing layers of flexible pavements as well as in subgrade soils has been analysed and modelled in both dry and wet conditions. Furthermore, it is discussed a new simulation-based methodology for the detection of the fouling content in railway ballast. Concerning the mechanical parameters, experimental based methods are presented for the assessment of the strength and deformation properties of the soils and the top-bounded layers of flexible pavements.\ud Furthermore, unique case studies in terms of the methodology proposed, the survey planning and the site\ud procedures in rather complex operations, are discussed in the case of bridges and tunnels inspections.

Ground-penetrating radar (GPR) is being increasingly used for pavements maintenance due to the wide range of\ud applications spanning from physical to geometrical inspections, thereby allowing for a reliable diagnosis of the main causes of road structural damages.\ud In this work, an off-ground GPR system was used to investigate a large-scale rural road network. Two sets of\ud surveys were carried out in different time periods, with the main goals to i) localize the most critical sections; ii) monitor the evolution of previous damages and localize newborn deep faults, although not revealed at the pavement surface level; iii) analyze the causes of both evolution and emergence of faults by considering environmental and human factors.\ud A 1-GHz GPR air-launched antenna was linked to an instrumented van for collecting data at traffic speed. Other support techniques (e.g. GPS data logger, odometer, HD video camera) were used for cross-checking,. Such centre frequency of investigation along with a 25-ns time window allow for a signal penetration of 900 mm, consistent with the deepest layer interfaces. The bottom of the array was 400 mm over the surface, with a minimum distance of 1200 mm from the van body. Scan length of maximum 10 km were provided for avoiding heavy computational loads.\ud The rural road network was located in the District of Rieti, 100 km north from Rome, Italy, and mostly develops\ud in a hilly and mountainous landscape. In most of the investigated roads, the carriageway consists in two lanes of 3.75 meters wide and two shoulders of 0.50 meters wide. A typical road section includes a HMA layer (65 mm\ud average thickness), a base layer (100 mm average thickness), and a subbase layer (300 mm average thickness), as described by pavement design charts.\ud The first set of surveys was carried out in two days at the beginning of spring in moderately dry conditions.\ud Overall, 320-km-long inspections were performed in both travel directions, thereby showing a productivity of\ud approximately 160 km/day at 40 km/h speed, on the average.\ud After processing and first-checking, GPR profiles were divided into homogeneous sections according to the combination of different parameters (e.g. route analyzed, long distance conditions of regularity/irregularity in layers arrangement). In such context, a high consistency between surface damages, mismatches from the GPR scans,\ud and boundary environmental conditions was demonstrated. In addition, deep mismatches were detected even for\ud early-stage or unrevealed faults.\ud The second set of surveys was carried out in autumn in high humidity conditions, due to recent rainfalls. 160 km\ud of relevant routes from the same road network were investigated.\ud Results showed a high consistency with those collected during the first-stage of surveys. Minor changes were\ud found in those sections with low traffic loads (e.g. farther away from the biggest town of Rieti), whereas major mismatches were detected in wetlands (e.g. close to rivers), work zones, and nearby those sections already deeply damaged in the past.\ud This work benefited from networking activities carried out within the EU funded COST Action TU1208 “Civil\ud Engineering Applications of Ground Penetrating Radar”.

The overall objective of this work is to contribute to knowledge concerning if, when and how much mobile phone use affects the safety of driving. The work entails analysing driving performance while using different mobile equipment in different road configurations and in the specific case of a critical driving situation. Three different scenarios were implemented in the driving simulator of the Inter-Universities Research Centre for Road Safety (CRISS) at Roma Tre University: an urban road, a two-lane rural road and a highway. Thirty drivers were asked to answer a phone call while driving, using different mobile equipment: hand-held, hands-free and hands-free voice-activated cellular phone. The effects of using the mobile phone were also compared to the baseline condition (no phone conversation). Driving performance, under car-following conditions, were collected and statistically analysed when a sudden braking of the leading vehicle occurred. The main results demonstrated that the driver’s speed generally reduced during the phone call, as a compensatory action to the decrease in the driver’s reaction capability, as shown by the generally increased reaction time, especially under certain driving conditions (urban road, along tangent, using hand-held mobile device). This study provided an investigation on the effects of using a mobile phone while driving; highlighted the worst combinations of the variables investigated; and demonstrated that some reductions in driving performance were revealed under critical road situations, especially in the urban environment, even when using mobile equipment that is permitted by the regulations of several countries.

Ground-penetrating radar (GPR) is considered as one of the most flexible geophysical tools that can be effectively and efficiently used in many different applications. In the field of pavement engineering, GPR can cover a wide range of uses, spanning from physical to geometrical inspections of pavements. Traditionally, such inferred information are integrated with mechanical measurements from other traditional (e.g. plate bearing test) or non-destructive (e.g. falling weight deflectometer) techniques, thereby resulting, respectively, in time-consuming and low-significant measurements, or in a high use of technological resources. In this regard, the new challenge of retrieving mechanical properties of road pavements and materials from electromagnetic measurements could represent a further step towards a greater saving of economic resources. As far as concerns unpaved and bound layers it is well-known that strength and deformation properties are mostly affected, respectively, by inter-particle friction and cohesion of soil particles and aggregates, and by bitumen adhesion, whose variability is expressed by the Young modulus of elasticity. In that respect, by assuming a relationship between electromagnetic response (e.g. signal amplitudes) and bulk density of materials, a reasonable correlation between mechanical and electric properties of substructure is therefore expected. In such framework, a pulse GPR system with ground-coupled antennae, 600 MHz and 1600 MHz centre frequencies was used over a 4-m×30-m test site composed by a flexible pavement structure. The horizontal sampling resolution amounted to 2.4×10-2 m. A square regular grid mesh of 836 nodes with a 0.40-m spacing between the GPR acquisition tracks was surveyed. Accordingly, a light falling weight deflectometer (LFWD) was used for measuring the elastic modulus of pavement at each node. The setup of such instrument consisted of a 10-kg falling mass and a 100-mm loading plate so that the influence domain of the elasticity measure could be comparable to that of the radar signal. Good agreement were found between high Young modulus values and repaved zones, whereas damaged areas were characterized by lower values of E. Tomographic maps of amplitudes along the z axis were extracted up to a depth of z < 200 mm, consistent with the depth domain of the LFWD, and some values on the nodes were randomly selected and thus related to the corresponding elastic modulus both for calibration and validation of the model. Comparison between predicted and measured elastic modulus showed relatively good results. Percentage errors ranging from -44% and +34% demonstrated an overall underestimate of the model with respect to the real truth. Future research activities could be addressed towards an improvement of the model by calibrating in laboratory environment under controlled conditions, and by using different GPR centre frequencies of investigation. This work benefited from networking activities carried out within the EU funded COST Action TU1208 “Civil Engineering Applications of Ground Penetrating Radar”.

This work aims at presenting the first-year activities and results of COST (European COoperation in Science and Technology) Action TU1208 “Civil Engineering Applications of Ground Penetrating Radar”. This Action was launched in April 2013 and will last four years. The principal aim of COST Action TU1208 is to exchange and increase scientific-technical knowledge and experience of GPR techniques in civil engineering, whilst simultaneously promoting throughout Europe the effective use of this safe and non-destructive technique in the monitoring of infrastructures and structures. Moreover, the Action is oriented to the following specific objectives and expected deliverables: (i) coordinating European scientists to highlight problems, merits and limits of current GPR systems; (ii) developing innovative protocols and guidelines, which will be published in a handbook and constitute a basis for European standards, for an effective GPR application in civil- engineering tasks; safety, economic and financial criteria will be integrated within the protocols; (iii) integrating competences for the improvement and merging of electromagnetic scattering techniques and of data- processing techniques; this will lead to a novel freeware tool for the localization of buried objects, shape-reconstruction and estimation of geophysical parameters useful for civil engineering needs; (iv) networking for the design, realization and optimization of innovative GPR equipment; (v) comparing GPR with different NDT techniques, such as ultrasonic, radiographic, liquid-penetrant, magnetic-particle, acoustic-emission and eddy-current testing; (vi) comparing GPR technology and methodology used in civil engineering with those used in other fields; (vii) promotion of a more widespread, advanced and efficient use of GPR in civil engineering; and (viii) organization of a high-level modular training program for GPR European users. Four Working Groups (WGs) carry out the research activities. The first WG focuses on the design of innovative GPR equipment, on the building of prototypes and on the testing and optimisation of new systems. The second WG focuses on the GPR surveying of pavement, bridges, tunnels and buildings, as well as on the sensing of underground utilities and voids. The third WG deals with the development of electromagnetic forward and inverse scattering methods, for the characterization of GPR scenarios, as well as with data- processing algorithms for the elaboration of the data collected during GPR surveys. The fourth WG works on the use of GPR in fields different from the civil engineering, as well as on the integration of GPR with other non-destructive testing techniques. Each WG includes several Projects. COST Action TU1208 is active through a range of networking tools: meetings, workshops, conferences, training schools, short-term scientific missions, dissemination activities. During the first year of activities, a First General Meeting was organized in Rome, in July 2013, a second meeting took place in Nantes, in February 2014, and the Second General Meeting is being held jointly with the 2014 EGU General Assembly. A training school on "Microwave Imaging and Diagnostics: Theory, Techniques, and Applications", held in March 2014, was co-organised with the European School of Antennas. Four Short-Term Scientific Missions were funded, allowing young researchers to spend a period of time in an institution abroad, in order to carry out a research project contributing to the scientific objectives of the Action. The Action’s activities were disseminated in international conferences [1]-[4], as well as in further workshops and meetings. Two volumes were published [5]-[6], and several scientific papers on peer-reviewed journals. A Springer book presenting the state of the art on civil engineering applications of Ground Penetrating Radar is being prepared and is going to be published in summer 2014. A COST Action is a wide bottom-up interdisciplinary science and technology network, open to researchers from universities, public and private research institutions, as well as to NGOs, industry and SMEs. At present, About 100 Institutions from 24 COST Member Countries (Austria, Belgium, Croatia, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Italy, Latvia, Malta, Macedonia, The Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Switzerland, Turkey, United Kingdom) have already joined the Action, together with an Institution from Armenia (Near Neighbour Country, NNC). Beyond European borders, six Institutions from U.S.A., one from Rwanda and one from Australia have joined the Action. Further applications from two NNCs (Egypt and Ukraine) and International Partner Countries (Hong Kong and Japan) are under examination. COST Action TU1208 is still open to the participation of new parties and it is possible to include, in the scientific work plan, new perspectives and activities. Scientists and scientific institutions willing to join COST Action TU1208 are encouraged to contact the Chair of the Action and to follow the procedure described at http://www.cost.eu/participate/join_action. For more information on COST Action TU1208, please visit www.GPRadar.eu. —————————– Acknowledgement The Authors thanks COST for funding COST Action TU1208.

International audience

In many fields of civil engineering, the needs for innovative sensing technologies are growing. Ground-penetrating radar (GPR) is actually one of the most advanced sensing technologies available, allowing a nonintrusive inspection of the materials under investigation. GPR uses radar pulses to image the subsurface, exploiting electromagnetic (EM) radiation and then detecting the reflected signals from subsurface structures. This chapter provides an overview of GPR sensing technologies for civil engineering applications and related research topics. In particular, a number of promising concepts for GPR are introduced and discussed in this chapter, starting from the theoretical EM background of GPR signal propagation in soils and construction materials. Then, we illustrate the applications of GPR to civil engineering fields, from the construction and inspection of transportation infrastructures and hydraulic works, to geotechnical surveys, environmental monitoring, as well as building and bridge structural assessments. We will demonstrate why GPR is currently considered as one of the most effective and efficient sensing technologies and is a potential candidate to become the best available remote-sensing technology for civil engineering applications. Finally, a wide literature review will be presented in order to give the reader all of the sources of information useful for any in-depth study.

Ground Penetrating Radar (GPR) can be effectively used for non-destructive testing of composite structures and diagnostics affecting the whole life-cycle of civil engineering works. Nevertheless, few recognised international standards exist in this field and inhomogeneous recommendations are present in different countries. Moreover, the levels of knowledge, awareness and experience regarding the use of GPR in civil engineering vary strongly across different European areas. The COST Action TU1208 is working hard on leveraging these differences, by sharing and disseminating knowledge and experience, as well as by developing guidelines and protocols for a safe and effective use of GPR in civil engineering. GPR users need to know which is the best way to conduct GPR measurements and what the quality level for the results should be. The TU1208 guidelines will ensure a higher efficiency and quality of GPR services and they will constitute a scientific basis for the introduction of European Standards on the application of GPR in civil engineering. The aim of this contribution is to present an in-depth overview and critical analysis of the existing GPR international and national standards and guidelines. The main documents considered in our work are listed and briefly described in the following. Three standards are provided by the American Society for Testing and Materials (ASTM), to guide the GPR use for subsurface investigation, evaluation of asphalt-covered concrete bridge decks, and determination of pavement-layer thickness: 1. ASTM D6432-11, Standard Guide for Using the Surface Ground Penetrating Radar Method for Subsurface Investigation, ASTM International, West Conshohocken, PA, 2011, www.astm.org, DOI: 10.1520/D6432-11. 2. ASTM D6087-08, Standard Test Method for Evaluating Asphalt-Covered Concrete Bridge Decks Using Ground Penetrating Radar, ASTM International, West Conshohocken, PA, 2008, www.astm.org, DOI: 10.1520/D6087-08. 3. ASTM D4748-10, Standard Test Method for Determining the Thickness of Bound Pavement Layers Using Short-Pulse Radar, ASTM International, West Conshohocken, PA, 2010, www.astm.org, DOI: 10.1520/D4748-10. Further ASTM standards exist, not focused on GPR but including useful information (details are not provided here, for brevity reasons). There are no standards in Europe, instead, guiding the GPR use for subsurface prospecting and regulating the numerous applications of this non-destructive technique. The following Radio and Telecommunications Terminal Equipment (RTTE) directive applies to GPR equipment and allows the placing of a GPR product on the European (EU) market for sale: Directive 1999/5/EC of the European Parliament and of the Council of 9 March 1999, on radio equipment and telecommunications terminal equipment and the mutual recognition of their conformity. Official Journal of the European Union, L 91, 7.4.1999, open access on ec.europa.eu. This document will be repealed, since 13 June 2016, by the following RTTE directive: Directive 2014/53/EU of the European Parliament and of the Council of 16 April 2014, on the harmonisation of the laws of the Member States relating to the making available on the market of radio equipment, repealing Directive 1999/5/EC. Official Journal of the European Union, L 153, 22.5.2014, open access on ec.europa. Although conformance to the RTTE directive allows the placing of a GPR product on the market for sale, it does not give authority for its use. In order to use the equipment, in the majority of EU member countries, a license is required. The license is controlled and issued by the radio administration in each of the member countries. The Electronic Communications Committee (ECC) of the European Conference of Postal and Telecommunications Administrations (CEPT) considers and develops policies on electronic communications activities in European context, taking account of European and international legislations and regulations. There are 48 European countries involved in the CEPT, which cooperate to regulate posts, radio spectrum and communications networks in Europe. The ECC agreed to the decision ECC/DEC/(06)08, specifically referred to GPR and Wall Penetrating Radar (WPR) systems: ECC Decision of 1 December 2006 on the conditions for use of the radio spectrum by Ground- and Wall- Probing Radar (GPR/WPR) imaging systems, 14 December 2006, open access on www.cept.org. This is not legally binding on member countries. It is currently implemented by 25 and partly implemented by 2 of the 48 administrations; 5 further administration are considering and studying the decision. Outside Europe, different approaches exist, ranging from very formal technical approval and licensing conditions to no specific rules. A series of standards and codes, introduced by the European Telecommunications Standards Institute (ETSI), regulate the GPR use and its emissions of electromagnetic radiation in Europe: 1. ETSI EN 301 489-1 v1.9.2, Electromagnetic compatibility and Radio spectrum Matters (ERM); ElectroMagnetic Compatibility (EMC) standard for radio equipment and services; Part 1: Common technical requirements, Sept. 2011, open access on www.etsi.org, Ref. DEN/ERM-EMC-230-32, 45 pp. [7]. This document is a Harmonized European Standard. 2. ETSI EN 301 489-32 v1.1.1, Electromagnetic compatibility and Radio spectrum Matters (ERM); ElectroMagnetic Compatibility (EMC) standard for radio equipment and services; Part 32: Specific conditions for Ground and Wall Probing Radar applications, Sept. 2009, open access on www.etsi.org, Ref. DEN/ERM-EMC-230-32, 12 pp. [8]. This document is currently (May 2015) a Candidate Harmonized European Standard (Telecommunication Series). 3. ETSI EN 302/066-1 v1.2.1, Electromagnetic compatibility and Radio spectrum Matters (ERM); Ground- and Wall- Probing Radar applications (GPR/WPR) imaging systems; Part 1: Technical characteristics and test methods, Dec. 2007, open access on www.etsi.org, Ref. REN/ERM-TG31A-0113-1, 25 pp. [9]. This document is a Harmonized European Standard (Telecommunications series). 4. ETSI EN 302/066-2 v1.2.1, Electromagnetic compatibility and Radio spectrum Matters (ERM); Ground- and Wall- Probing Radar applications (GPR/WPR) imaging systems; Part 2: Harmonized EN covering essential requirements of article 3.2 of the RTTE Directive, Dec. 2007, open access on www.etsi.org, Ref. REN/ERM-TG31A- 0113-2, 12 pp. [10]. This document is a Harmonized European Standard (Telecommunications series). 5. ETSI EG 202 730 v1.1.1, Electromagnetic compatibility and Radio spectrum Matters (ERM); Code of Practice in respect of the control, use and application of Ground Probing Radar (GPR) and Wall Probing Radar (WPR) systems and equipment, Sept. 2009, open access on www.etsi.org, Ref. DEG/ERM-TGUWB-010, 11 pp. [11]. This document is currently (May 2015) an ETSI guide. Few National GPR Guidelines and Standards exist in Europe. In France, the National standard NF S 70-003, Parts 1-3, is concerned with the use of GPR to detect buried utilities. Still in France, Cerema/Ifsttar produced protocols for road inspection. In Germany, the DGZfP e.V. (German Society for Non-Destructive Testing) published a fact sheet called “Merkblatt B10” on the radar method for non-destructive testing in civil engineering (2008). Still in Germany, there is a BASt (Federal Highway Administration) instruction sheet on the use of GPR to gain inventory data of road structure (2003). In Poland, the national regulation of September 24, 1998 (Dz.U. Nr 126 poz. 839) cites ‘georadar testing’ as a method to investigate the soil structure. In Scandinavia, recommendations for guidelines were developed during the MARA NORD Project (2010-2012) on the use of GPR in asphalt air voids content measurements, in road construction quality control, in bridge deck surveys, in road rehabilitation projects and in site investigations. \ud Acknowledgement This work stems from the research activities of COST (European COoperation in Science and Technology) Action TU1208 “Civil engineering applications of Ground Penetrating Radar.” The Authors thank COST (www.cost.eu) for funding the Action TU1208 (www.GPRadar.eu). Part of this work was carried out during the Short-Term Scientific Mission STSM-TU1208-24656 “Comparative study of GPR international standards and guidelines” (Dr Lara Pajewski, Italy, visiting Prof Marian Marciniak, Poland).

Clay content is one of the primary causes of pavement damages, such as subgrade failures, cracks, and pavement rutting, thereby playing a crucial role in road safety issues as an indirect cause of accidents. In this paper, several ground-penetrating radar methods and analysis techniques were used to nondestructively investigate the electromagnetic behaviour of sub-asphalt compacted clayey layers and subgrade soils in unsaturated conditions. Typical road materials employed for load-bearing layers construction, classified as A1, A2, and A3 by the American Association of State Highway and Transportation Officials soil classification system, were used for the laboratory tests. Clay-free and clay-rich soil samples were manufactured and adequately compacted in electrically and hydraulically isolated formworks. The samples were tested at different moisture conditions from dry to saturated. Measurements were carried out for each water content using a vector network analyser spanning the 1 GHz–3 GHz frequency range, and a pulsed radar system with ground-coupled antennas, with 500-MHz centre frequency. Different theoretically based methods were used for data processing. Promising insights are shown to single out the influence of clay in load-bearing layers and subgrade soils, and its impact on their electromagnetic response at variable moisture conditions.

Even though there is plenty of literature contributions related to the non-destructive evaluation of road pavements using ground-penetrating radar (GPR), with several purposes spanning from the layer thicknesses evaluation to the detection of highly wet spots in the subsurface, there is still a lack of highly-reliable results concerning the mechanical assessment of road pavements, by using this technology. This work endeavours to face this topic and proposes a semi-empirical model for predicting the elastic modulus of a flexible pavement, by employing GPR. Data were collected over three different road sections within the districts of Madrid and Guadalajara, Spain. In particular, GPR surveys were carried out at the speed of traffic over the roads N320 and N211 in the district of Gadalajara and the road N320 in the district of Madrid, for a total of 39 kilometers, approximately. In particular, air-coupled radar systems with a 1000 MHz center frequency antenna and two different 2000 MHz center frequency antennas, mounted onto an instrumented vehicle, were here employed. The calibration of the model was then performed by exploiting ground-truth data coming from other non-destructive technologies. In more details, an instrumented lorry equipped with a curviameter, namely, a deflection tool capable to collect and process continuously and in real time the mechanical response of the flexible pavement, was used in the above road sections. Promising results are here presented, and the potential of GPR for monitoring the mechanical performances of a road network is also proved. \ud Acknowledgement The Authors thank COST, for funding the Action TU1208 "Civil Engineering Applications of Ground Penetrating Radar."

This study aims at proposing a model capable to assess the physical conditions of railway ballast, in terms of percentage of fouling within the material, by analyzing its electromagnetic response. For the calibration of such a model, a laboratory set-up was implemented in order to reproduce a real-scale railway environment. In more details, a 1.47 m long × 1.47 m wide × 0.48 m high plexiglass formwork was laid over a metal sheet, to define a proper domain of investigation. The formwork was then filled up with railway ballast, progressively fouled with a fine-grained pollutant material, namely, an A4 soil type according to the ASSHTO soil classification. At each step of fouling percentage, electromagnetic surveys were carried out by employing several ground-penetrating radar (GPR) systems, in both ground-coupled and air-coupled configurations. On the other hand, the validation of the model was performed through a simulation-based approach. In particular, the main physical and geometrical properties of each ballast-pollutant configuration were reproduced by means of a random sequence absorption (RSA) approach. For the representation of the shape of the solid matrix of the ballast, a relatively complex geometry was here adopted. Finally, the developed geometries were processed by the GprMax 2D numerical simulator, employing a finite-difference time domain (FDTD) model capable of generating a synthetic GPR response for the several configurations analysed in laboratory environment. As result, the potential of the combined use of RSA and FDTD approaches is demonstrated, and a model for characterizing such a complex coarse-grained heterogeneous material is finally proposed. \ud Acknowledgement The Authors thank COST, for funding the Action TU1208 "Civil Engineering Applications of Ground Penetrating Radar."

This work aims at disseminating the ongoing research activities and third-year results of the COST (European COoperation in Science and Technology) Action TU1208 “Civil Engineering Applications of Ground Penetrating Radar.” About 350 experts are participating to the Action, from 28 COST Countries (Austria, Belgium, Croatia, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Ireland, Italy, Latvia, Malta, Macedonia, The Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey, United Kingdom), and from Albania, Armenia, Australia, Colombia, Egypt, Hong Kong, Jordan, Israel, Philippines, Russia, Rwanda, Ukraine, and United States of America. In September 2014, TU1208 has been recognised among the running Actions as “COST Success Story” (“The Cities of Tomorrow: The Challenges of Horizon 2020,” September 17-19, 2014, Torino, IT - A COST strategic workshop on the development and needs of the European cities). The principal goal of the COST Action TU1208 is to exchange and increase scientific-technical knowledge and experience of GPR techniques in civil engineering, whilst simultaneously promoting throughout Europe the effective use of this safe and non-destructive technique in the monitoring of infrastructures and structures. Moreover, the Action is oriented to the following specific objectives and expected deliverables: (i) coordinating European scientists to highlight problems, merits and limits of current GPR systems; (ii) developing innovative protocols and guidelines, which will be published in a handbook and constitute a basis for European standards, for an effective GPR application in civil- engineering tasks; safety, economic and financial criteria will be integrated within the protocols; (iii) integrating competences for the improvement and merging of electromagnetic scattering techniques and of data- processing techniques; this will lead to a novel freeware tool for the localization of buried objects, shape-reconstruction and estimation of geophysical parameters useful for civil engineering needs; (iv) networking for the design, realization and optimization of innovative GPR equipment; (v) comparing GPR with different NDT techniques, such as ultrasonic, radiographic, liquid-penetrant, magnetic-particle, acoustic-emission and eddy-current testing; (vi) comparing GPR technology and methodology used in civil engineering with those used in other fields; (vii) promotion of a more widespread, advanced and efficient use of GPR in civil engineering; and (viii) organization of a high-level modular training program for GPR European users. Four Working Groups (WGs) carry out the research activities. WG 1 focuses on the design of innovative GPR equipment, on the building of prototypes and on the testing and optimisation of new systems. WG 2 focuses on the GPR surveying of pavement, bridges, tunnels and buildings, as well as on the sensing of underground utilities and voids. WG 3 deals with the development of electromagnetic forward and inverse scattering methods, for the characterization of GPR scenarios, as well as with data-processing algorithms for the elaboration of the data collected during GPR surveys. WG 4 works on the use of GPR in fields different from the civil engineering, as well as on the integration of GPR with other non-destructive testing techniques. Each WG includes several Projects. COST Action TU1208 is active through a range of networking tools: meetings, workshops, conferences, training schools, short-term scientific missions, dissemination activities. For more information on COST Action TU1208, please visit www.GPRadar.eu and www.cost.eu. \ud Acknowledgement The Authors wish to thank COST, for funding the COST Action TU1208 “Civil engineering applications of Ground Penetrating Radar."

A significant open issue concerning the reliability of geophysical methods and in particular of ground penetrating radar (GPR), both in research and professional context, is a general lack of international standards. This is a major problem to be faced, in order to gain scientific strictness for the GPR practices, and to easily extend to the international community the results achieved within the area of single virtuous countries. Producing international guidelines can represent an important step forward, in this sense. In the memorandum of understanding of the COST Action TU1208 is clearly stated that one of the main purposes of the Action is the “development of innovative protocols and guidelines which will be published in a handbook and constitute a basis for European Standards, for an effective GPR application in CE tasks; safety, economic and financial criteria will be integrated within the protocols”. Of course this is not a simple task to be accomplished. Firstly, survey procedures are highly dependent on the objective of the survey itself. On the basis of the objective of each geophysical test, the GPR system, the antenna configuration, and even the processing procedures may change. Besides, these procedures are also influenced by the environmental conditions in which the tests are performed. This affects several aspects spanning from hardware to software, but including, for instance, also safety issues. Due to these reasons, one of the main goal of the COST Action TU1208 is the development of several guidelines related to the main applications of GPR in the field of civil engineering. In this work, the structure of a guidelines handbook for GPR activities in tunnels is outlined. In the first sections, the principal references in the field are provided, and the most common GPR equipment and complementary technologies are described. Subsequently, the survey methodologies are explained. Particular attention is paid to the preliminary activities to be carried out prior to the GPR surveys, which can cover an important role in such a complex environment. Lastly, the main applications of GPR technology in tunnels are discussed. \ud Acknowledgement The Authors thank COST, for funding the Action TU1208 "Civil Engineering Applications of Ground Penetrating Radar."