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Railway infrastructure managers run dedicated inspection vehicles to monitor the geometric quality of the track (among other aspects) to detect irregularities and ensure safe running conditions of railway lines, in accordance with specific regulations. Unfortunately, these inspections disturb the normal traffic operation, especially in networks with intense traffic; are generally carried out only a few times per year; and, consequently, do not provide prompt identification of critical situations. Considering the recent developments and cost reduction in sensing capabilities of smartphones, the authors present an approach to use these technologies to perform constant acceleration measurements inside in-service trains to complement the assessment of the structural performance and geometrical degradation of the tracks. Cross-correlation values above 0.85 were obtained between the standard deviations of the longitudinal level and the experimental vertical accelerations measured on-board a passenger train on an 11-km railway stretch. The results showed that the approach can be used to identify critical situations that affect the performance of the track, regarding passenger comfort, degradation rates, and risk of derailment. It may comprise a low-cost and crowdsourced complement to the general current practice of track geometric inspection by dedicated vehicles and contribute to an earlier detection of track malfunctions, consequently, to a more efficient maintenance planning and infrastructure management. [ABSTRACT FROM AUTHOR]

Each year, there can be three to six millions of service train axles running over an open plain track. In fact, these trains could impose a variety of dynamic loading conditions depending on the wheel and rail maintenance levels. Inevitably, the risk of high-intensity dynamic loading conditions by wheel-rail interactions due to wheel or rail irregularity cannot be disregarded. Imperfection of rail tracks could lead directly to the exceedance of permissible stress of a track component and later amplify rapid track deterioration rates causing cracking in sleepers and failure of track substructure. Practical railway track irregularities can be typically classified into short wave length (high frequency) and long wave length (low frequency) defects, of which previous researchers had studied each in isolation. This paper is the first to study the influence on railway track inspection and maintenance priorities caused by the coupling of wave lengths between dipped rail joint and differential track settlements. To study the dynamic coupling effects, P1 and P2 forces are evaluated at the track irregularity together with rail/sleeper contact force, ballast pressure and bending moments of sleepers using dynamic multi-body simulation approach. It is found that some patterns of coupling irregularity could cause a significant reduction in dynamic impact factors whilst some are associated with an increase in the wheel/rail impact force. The insight has then been integrated to establish track performance indicators that are paramount for prioritising track inspection and maintenance. [ABSTRACT FROM AUTHOR]

Magnetic Flux Leakage (MFL) method is widely used in non-destructive testing of ferromagnetic specimens such as steel pipes, ropes and rails. Inspection velocity is a critical factor in online rail track evaluation due to specific inspection conditions. As the speed increases the distribution of magnetic induction inside rail becomes inhomogeneous primarily under the influence of eddy currents. This complicates MFL signals interpretation and reduces the ability to detect deep subsurface defects in the rail head. In this paper we explore the speed limitations of the traditional MFL rail inspection and contemplate the ways to overcome the said limitations. To investigate the dependence of flux leakage data on inspection velocity two different methods were applied. The first one is 3D computer simulation of interaction between the fixed rail and the moving magnetizing system. The second method is the set of field measurements in which an experimental setup consisted of electromagnets and sensors moved along rail with artificially made defects. The results of both methods indicate to detect defects located in the center of the rail head at speeds over 80 km/h the distance between magnetizing system poles should exceed conventional 3 m or some alternatives should be employed such as MFL remote field analysis. [ABSTRACT FROM AUTHOR]

Rails are among the most important components of railway transportation, and real-time defects detection of the railway is an important and challenging task because of intensity inhomogeneity, low contrast, and noise. This paper presents an automatic railway visual detection system (RVDS) for surface defects and focuses on several key issues of RVDS. First, in view of challenges such as complex condition and orbital reflectance inequality, we put forward a region-of-interest detection region extraction algorithm by vertical projection and gray contrast algorithm. In addition, a curvature filter equipped with implicit computing and surface preserving power is studied to eliminate noise and keep only the details. Then, an improved fast and robust Gaussian mixture model based on Markov random field is established for accurate and rapid surface defect segmentation. Additionally, an expectation–maximization algorithm is applied to optimize the parameters. The experimental results demonstrate that the proposed method performs well with both noisy and railway images, which enables identification and segmentation of the defects from rail surface, achieving detection performance with 92% precision and 88.8% recall rate on average, and is robust compared with the related well-established approaches. [ABSTRACT FROM AUTHOR]

The aim was the perfection of an analytic examination, which describes the track deterioration process, characterized the correspondences more precisely and better to use in practice. This method was based on the destruction's theory of the railway track geometry and it exploited the possibilities of recent computer technology. More than one million measuring car (FMK-004) data were processed than analyzed and defined by configuring and programming a new method. The results of this method were descriptive functions, which afford interpretable information about the geometrically destruction's occurrences of the different railway lines. [ABSTRACT FROM AUTHOR]

The modern constructions of tram tracks are very various. Presently at construction, repair and current maintenance of the tracks it is important to consider not only economic indicators (capital and operating costs) and technical features (speed, carrying capacity, travel time), but esthetic attractiveness. Lately much attention is given to the ecological factors (noise, vibration and environmental pollution). Especially this is important to consider in historical districts. This article is devoted to choosing of the most effective type of public passenger transport, methods of ground of usable area of tram and ways of their expansion, taking into account the stated factors. For justification of such decisions is proposed the mathematical model and calculation of the integral of the discounted cost of the three designs of tram ways, at different solving these problems. Also in this work identifies the main actions for increase of competitiveness and efficiency of investments into modernization of existing and construction of new tram lines, which allows to significantly expand the scope of its application. [ABSTRACT FROM AUTHOR]

High-accuracy railway track surveying is essential for railway construction and maintenance. The traditional approaches based on total station equipment are not efficient enough since high precision surveying frequently needs static measurements. This paper proposes a new filtering and smoothing algorithm based on the IMU/odometer and landmarks integration for the railway track surveying. In order to overcome the difficulty of estimating too many error parameters with too few landmark observations, a new model with completely observable error states is established by combining error terms of the system. Based on covariance analysis, the analytical relationship between the railway track surveying accuracy requirements and equivalent gyro drifts including bias instability and random walk noise are established. Experiment results show that the accuracy of the new filtering and smoothing algorithm for railway track surveying can reach 1 mm (1σ) when using a Ring Laser Gyroscope (RLG)-based Inertial Measurement Unit (IMU) with gyro bias instability of 0.03°/h and random walk noise of 0.005°√ p h while control points of the track control network (CPIII) position observations are provided by the optical total station in about every 60 m interval. The proposed approach can satisfy at the same time the demands of high accuracy and work efficiency for railway track surveying. [ABSTRACT FROM AUTHOR]

Rail joints are a weak component in railway tracks because of the large impact and wheel-rail contact forces. Every train passage contributes to the deterioration of rail joints, causing visible (e.g., battered rails) and invisible (e.g., loose bolts) damages. The invisible damage cannot be detected by the commonly performed visual inspection, which is labor intensive, unreliable, intrusive, and unsafe. In this paper, a vehicle-borne monitoring system is used to automatically detect and assess the tightness condition of bolts at rail joints. The monitoring method is developed based on field axle box acceleration (ABA) measurements using different bolt tightness conditions. The suitability of the method is assessed by bolt tightness prediction and verification of a set of rail joints in the tram network of Sheffield, UK. The results show that ABA system can be employed to monitor bolt tightness conditions at rail joints. With this information, better planning for selective preventive maintenance actions can be taken over rail joints. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Track inspection is purposely performed to recover tracks from defects and damage and eliminate potential safety hazards. It is scheduled through an exhaustive process that usually integrates many disciplines such as optimization, statistics, risk management, etc. Spending so much of a monetary and an emotional investment in an original schedule (referred to as master schedule hereafter) that the scheduler wants to deliver might be a good excuse not to develop a solid ‘Plan B’. Plan B here refers to scheduler responses or a contingency plan when the master schedule does not go as expected. It is found that there is often low to moderate probability of a crisis occurring when a schedule is executed in a real environment. Nevertheless, its impact can leave transportation services to the mercy of the disruption as shown by the Christmas 2014 incident where a huge volume of passengers using King's Cross and Paddington services experienced both inconvenience and discomfort due to engineering delays and train disruption. Thus, this paper aims to discuss the potential of considering ‘Plan B’ or contingency plan if incidents arise that were not expected during track inspection schedule execution. Benefits, general guidelines and relevant strategies for creating a contingency plan are also discussed. We highlight the rationale to support the claim that an original schedule of track inspection jobs should be adapted to respond to a new context e.g. inspection vehicle machine breakdown, new inspection requests, man-made hazards, terrorist attack, extreme weather, climate change, etc. It is however proposed to develop an appropriate set of performance measure that is used to guide rescheduling in track inspection due to financial, equipment inventory, manpower, safety regulations, time and spatial constraints. [ABSTRACT FROM AUTHOR]

A new method for track inspection is developed to complement traditional geometric methods. An inertial measuring system and a specialized data treatment method is proposed to evaluate railway track safety, observed from the vehicle dynamic performance point of view. System equations for the inverse vehicle dynamic problem, augmented with the suspension torsion equation, are solved to estimate the wheels driving forces that are directly correlated with the vehicle safety traveling over an irregular track. Results of a measuring campaign on a railway wagon are used to evaluate the present system by direct positional comparison with lateral and vertical contact forces (L=V) safety ratio measured with two instrumented wheelsets (IWS) installed on the leading bogie of the wagon. Also, data collected and treated are compared with track geometry measurements. The results of quantified track safety present good agreement with those found using traditional measuring methods. This confirms the ability of the new method to detect the location of the highest potential hazard region, for optimized track maintenance purposes. The new system proves to be a promising method for track safety evaluation. [ABSTRACT FROM AUTHOR]

Information fusion technology based on inertial measurement unit (IMU) and visual sensor unit is a potentially effective solution for fast measuring of spatial alignment of railway track, and the key to this solution is to determine the relative pose between IMU and visual unit with high precision. In this paper, a two-step calibration method is proposed for its determination through a simple process. Firstly, a vertical space vector is adopted, and it can be obtained by the IMU through the acceleration of gravity. Similarly, another vertical space vector can also be fixed by the camera through the corners of a checkerboard, used as calibration board and vertically placed. And the rotation relationship between the IMU and the camera is obtained by using the property of parallel space vector. In the second step, the translation movement amounts of the IMU and camera are taken as the state vectors, where the translation amounts are estimated and determined by using the extended Kalman's filter (EKF). The method is experimentally tested and the results show that the proposed method is capable of determining the relative pose between IMU and camera with a fairly good precision. [ABSTRACT FROM AUTHOR]

The main aim of this report is to review the recent progress in the utilisation of Barkhausen noise and other magnetic testing methods for railway inspection and to provide a basis for follow-on research. This paper reviews the technologies currently employed along with examples of recent field applications. The three main research areas that this review focuses upon are the residual stress determination from rail tracks, the stress-free temperature (neutral temperature) determination with magnetic Barkhausen noise measurements and the study of the corrugation of railroads with Barkhausen noise. The Barkhausen noise features utilised in these studies are also reported. Finally, some preliminary measurements carried out on Finnish rail tracks with commercial Barkhausen noise equipment are presented. [ABSTRACT FROM AUTHOR]

Magnetic flux leakage (MFL) inspection is one of the most important and sensitive nondestructive testing approaches. For online MFL inspection of a long-range railway track or oil pipeline, a fast and effective defect profile estimating method based on a multi-power affine projection algorithm (MAPA) is proposed, where the depth of a sampling point is related with not only the MFL signals before it, but also the ones after it, and all of the sampling points related to one point appear as serials or multi-power. Defect profile estimation has two steps: regulating a weight vector in an MAPA filter and estimating a defect profile with the MAPA filter. Both simulation and experimental data are used to test the performance of the proposed method. The results demonstrate that the proposed method exhibits high speed while maintaining the estimated profiles clearly close to the desired ones in a noisy environment, thereby meeting the demand of accurate online inspection. [ABSTRACT FROM AUTHOR]

Subsidence and geometry deformation monitoring are essential for safe transportation on a high-speed railway. Terrestrial laser scanning (TLS) is able to collect dense three-dimensional point data from the survey scene and achieve highly accurate measurements; therefore, it is considered to be one of the most promising surveying techniques for railway track geometry deformation monitoring. This paper proposes a new approach that uses TLS to detect subsidence and irregularities in a track by fitting boundaries of the cross section of the track. In addition, for a section of local railway, an outdoor experiment was performed to ascertain the feasibility and accuracy of this method. The deformations detected with TLS were compared with the field measurements gathered with other methods such as those from a track inspection car. The results indicate that the subsidence difference between TLS and precise leveling is 2-3 mm, and the difference in the geometric parameters of the tracks is 1-2 mm. Finally, the possible causes of error involved with TLS are discussed. [ABSTRACT FROM AUTHOR]

The main goal of this paper is to model track geometry deterioration using a comprehensive field investigation gathered over a period of 2 years on approximately 180 km of railway line. Artificial neural networks (ANNs) were adapted for this research. The railway line was divided into analytical segments (ASs). For each AS, the following data were collected: track structure, traffic characteristics, track layout, environmental factors, track geometry, and maintenance and renewal data. ANN models were developed for the main track geometry parameters and produced significant relationships between the variables. In addition, sensitivity analyses were performed to compute the importance of each predictor in determining the neural network. The obtained results proved that ANN may be an alternative method for predicting track geometry deterioration. [ABSTRACT FROM AUTHOR]

In this paper, we present a real-time automatic vision-based rail inspection system, which performs inspections at 16 km/h with a frame rate of 20 fps. The system robustly detects important rail components such as ties, tie plates, and anchors, with high accuracy and efficiency. To achieve this goal, we first develop a set of image and video analytics and then propose a novel global optimization framework to combine evidence from multiple cameras, Global Positioning System, and distance measurement instrument to further improve the detection performance. Moreover, as the anchor is an important type of rail fastener, we have thus advanced the effort to detect anchor exceptions, which includes assessing the anchor conditions at the tie level and identifying anchor pattern exceptions at the compliance level. Quantitative analysis performed on a large video data set captured with different track and lighting conditions, as well as on a real-time field test, has demonstrated very encouraging performance on both rail component detection and anchor exception detection. Specifically, an average of 94.67 $\%$ precision and 93 $\%$ recall rate has been achieved for detecting all three rail components, and a 100 $\%$ detection rate is achieved for compliance-level anchor exception with three false positives per hour. To our best knowledge, our system is the first to address and solve both component and exception detection problems in this rail inspection area. [ABSTRACT FROM PUBLISHER]

Metropolitan railway transport has become an efficient solution to the mobility necessities in urban areas. Railway track maintenance tasks have to be improved and adjusted to metropolitan requirements, in particular the few hours available to operate due to the high frequency service offered. This paper describes and proposes an inertial monitoring system to detect and estimate track irregularities by using in-service vehicles. A new maintenance strategy is established, based on the railway track conditions and continuous monitoring is provided to do so. The system proposed consists of at least two accelerometers mounted on the bogie axle-box and a GPS (Global Positioning System). Lateral accelerations have been analyzed to study gauge and lateral alignment deviations. Accelerations have been treated and processed by high-pass filtering and validation has been carried out by comparison with measurements provided by a track monitoring trolley. Measurements were made on Line 1 of the Alicante metropolitan and tram network (Spain). [ABSTRACT FROM AUTHOR]

Railway turnouts are used to guide trains from one track to another and they are usually formed of a switch and a crossing (S&C). They pose both economic and safety issues since they need to be maintained, which is costly, and if not in a good state they can cause fatal railway accidents. The purpose of this research is to improve the inspection process for S&C, which is accomplished by: (1) identification of areas where research is needed and (2) research and development of a laser based trolley for the inspection of railway switches and crossings. The first step was carried out systematically and is described in the second section of this paper. With the output of the first step, as well as the help of Network Rail, it has been concluded that in Great Britain there is a need for a lightweight device that can carry out inspection for specific derailment hazards on switches and crossings as well as advise the welders on how they should be repaired. This research proposes a new approach for this issue by considering a lightweight laser based trolley system. The system is based on the ability to scan and record 2D slices of the parts that need to be inspected and calculate different wear indicators and derailment hazards in accordance with the Network Rail inspection standards. The work and findings of this research will also feed into the European project AUTOMAIN, Augmented Usage of Track by Optimisation of Maintenance, Allocation and Inspection of railway Networks, http://www.antomain.eu/. [ABSTRACT FROM AUTHOR]

Thousands of miles of railroad track must be inspected twice weekly by a human inspector to maintain safety standards. A computer vision system, consisting of field-acquired video and subsequent analysis, could improve the efficiency of the current methods. Such a system is prototyped, and the following challenges are addressed: the detection, segmentation, and defect assessment of track components whose appearance vary across different tracks and the identification and inspection of special track areas such as track turnouts. An algorithm that utilizes the periodic manner in which track components repeat in an inspection video is developed. Spectral estimation and signal-processing methods are used to provide robust detection of the periodically occurring track components. Results are demonstrated on field-acquired images and video. [ABSTRACT FROM PUBLISHER]

In the 1970s, a rolling contact fatigue defect that was christened a squat was identified on the British railway network, primarily at first on the West Coast Main Line. Two productive decades of international research on squats followed, which later contributed to a rapid understanding of gauge corner cracking, which differs in detail but is similar in many important respects to a classic squat. In the last 10–15 years, a rail defect that is superficially similar to the classic squat has appeared on several railways. This has been investigated in some detail, initially in Australia and more recently also in Europe as part of the Innotrack project. These investigations have both assumed that the investigated defect is a classic squat. This paper reviews research on the squat and on its younger cousin. It forms the basis for a companion paper that presents original observations from track and detailed metallurgical examinations of specimens of the more recent squat-type defect. The review in this paper is used in the companion paper to identify features of the two types of defects that are similar and those that are significantly different. [ABSTRACT FROM AUTHOR]

Abstract: With the development and operation of high speed trains, condition based maintenance becomes an important approach for the improvement of reliability and safety of rail transportation. This paper reports a feasibility study using pulsed eddy current thermography for imaging multiple cracks caused by rolling contact fatigue (RCF). After reviewing rail track inspection and RCF cracks, a PEC thermography system is introduced and applied to the imaging of multiple rolling contact fatigue cracks. Potential on-line inspection for rail track is also discussed. [Copyright &y& Elsevier]

With increased axle weight and faster trains, the need for routine inspection of rails becomes much more important. The approaches currently being used in the rail industry are either inspection trains, dual-purpose road/track vehicles or hand-held trolleys using ultrasonic, eddy current, alternating current field measurement (ACFM) or magnetic flux leakage sensors. The vehicle-mounted systems generally provide information on defect locations but less robust data about defect sizes, which can be provided by hand-held systems. In this research, a robotic system has been proposed for the detection and characterisation of rolling contact fatigue (RCF) cracks on in-service rail tracks, which is designed to locate and then systematically scan the defects to provide more detailed data on the cracks. The system consists of a mechanised trolley, an FS02N Kawasaki robot arm and a commercially available AMIGO ACFM system, supplied by TSC Inspection Systems. This paper outlines the experimental results when the trolley is stationary and the robot arm is used to survey the rail head. It has been shown that the proposed system has the potential to improve the quality of RCF crack characterisation and could be used to autonomously inspect the rail tracks. [ABSTRACT FROM AUTHOR]

Understanding track geometry deterioration decisively influences the planning and optimisation of track maintenance and renewal works and consequently the substantial related costs (savings) each year of every railway. To understand this deterioration it must be accurately modelled, paving the way towards its forecasting into the future. The main aim of the present study was to model railway track geometry deterioration using multivariate statistical analysis of the variables involved and to predict the future behaviour of the track geometry deterioration. For this purpose, a track section of about 180 km in length was selected as the base for the model and divided into analytical segments of as uniform characteristics as possible using a special segmentation algorithm. The lengths of the individual analytical segments were not identical, but were also kept as close to uniform as possible. For each analytical segment, the following general information was collected: track structure, traffic characteristics, track layout, environmental factors, track geometry measurements records and maintenance and renewal history data. Consequently, multivariate statistical analysis was performed on the main track geometry parameters: twist, level, alignment, gauge and cant. The coefficients of the independent variables involved in track geometry were found for each parameter in order to predict future behaviour for the purposes of efficient maintenance and renewal management [ABSTRACT FROM AUTHOR]

This paper presents a model simulating rail roughness growth in which the interaction of a wheelset with the track is considered. The aim is to investigate any possible mechanism for roughness growth due to the coupling between the vertical dynamics, the torsional vibration across the axle of the wheelset and the non-steady contact mechanics. The time-domain simulations are carried out for a driven wheelset on tangent track. Both rigid and flexible are considered with parameter variations for moments of the wheelset, vehicle speeds and wavelengths of initial roughnesses. The 2D non-Hertzian and non-steady contact model used in simulations are based on influence coefficients obtained from a boundary element model. The nonlinear development of the rail roughnesses after millions of wheelset passages is also presented. [ABSTRACT FROM AUTHOR]

The article focuses on the use of eddy current test method to detect early the development of fine crack pattern in rails known as rolling contact fatigue (RCF). It says that the rail inspection method is based on induction of electromagnetic that makes it to work without contact. It states that the technique, which is used on grinding trains, eddy current trolleys, and inspection trains in many European countries, is suitable for high speed tests required on test trains.

This article presents possibilities of application of selected geophysical methods in railway engineering. Geophysical methods are used to observe a physical field. The measured data are interpreted in order to provide findings on geotechnical conditions of railway substructure and its surroundings. Geophysical methods have been unsystematically applied on European railways in the past. This paper's text is supported mainly by the measurements performed under the INNOTRACK projects at the sites in the Czech Republic, France, Spain, and Sweden. The geophysical testing has proved that the geophysical methods can reliably, quickly, in detail, and at a relatively low cost, inform about the problematic zones of the track. The effect of the geophysical application can be enhanced by long-term monitoring of track segments. [ABSTRACT FROM AUTHOR]

Recent train accidents have reaffirmed the need for developing a rail defect detection system more effective than that currently used. One of the most promising techniques in rail inspection is the use of ultrasonic guided waves and non contact probes. A rail inspection prototype based on these concepts and devoted to the automatic damage detection of defects in rail head is the focus of this paper. The prototype includes an algorithm based on wavelet transform and outlier analysis. The discrete wavelet transform is utilized to denoise ultrasonic signals and to generate a set of relevant damage sensitive data. These data are combined into a damage index vector fed to an unsupervised learning algorithm based on outlier analysis that determines the anomalous conditions of the rail. The first part of the paper shows the prototype in action on a railroad track mock-up built at the University of California, San Diego. The mock-up contained surface and internal defects. The results from three experiments are presented. The importance of feature selection to maximize the sensitivity of the inspection system is demonstrated here. The second part of the paper shows the results of field testing conducted in south east Pennsylvania under the auspices of the U.S. Federal Railroad Administration. [ABSTRACT FROM AUTHOR]

Abstract: Nowadays, there are no systematic methodologies for evaluating life assessment of the rail, and few systems provide the measures of vertical and lateral forces that train exchanges with the rail. These systems are quite expensive and require the substitution of a portion of the track. In the present paper is presented a simple transducer (MPQY) for measuring, at the same time, the vertical and lateral forces. The easy installation and use of this instrument are its main characteristics. It is sufficient to put it in a hole, made in the rail web in the concurrence of the drilling axis, and connect it to the transmitting station for measuring for each convoy the vertical and lateral forces induced by each wheel. It can be also used for analysing speed and mass of trains and the specific derailment ratio. In addition, by using a damage model, it is possible to estimate the residual life of a rail. In order to do this, a linear model of rolling contact fatigue damage is implemented and tested with same experimental acquisitions. Another application of this transducer can be identified in the variation of the mechanical behaviour of ballast. In fact, by using the information coming from the MPQY and comparing it with the flexural moment measurement, it is possible to evaluate the variation of ballast behaviour with respect to time and set new parameters for ballast maintenance and train safety. [Copyright &y& Elsevier]

Some years ago, two railway inspection trains (RIT) already equipped with ultrasound, had additional advanced eddy current techniques installed. Recently, a new RIT was equipped with a system that was designed, from the beginning, to employ a combination of these two techniques for non-destructive rail inspection. The eddy current technique has been developed to enable identification and evaluation of rolling contact fatigue (RCF) defects. The ultrasound technique is aimed at measurements in the rail bulk volume, which are not feasible using the eddy current technique. Experience gained from application has shown that clear improvement on rail inspection can be achieved. For example, following Deutsche Bahn DB (German Rail) AG guideline, defects which are classified as group 2 using ultrasound testing can be further labelled as ‘distinguished positions’ if, for example, head checking can be identified in the same position using the eddy current technique. In other words, the new technique is capable of identifying two fundamentally different types of defects occurring at the same location. Such defects can then be classified as Group 1, equivalent according to the DB AG guideline. Furthermore, problem cases in the past, such as the decision whether a weld or rail joint is present for a fishing table, can be reliably determined using additional information from the eddy current technique. In this paper, examples will be provided to demonstrate application. [ABSTRACT FROM AUTHOR]

Recent train accidents have reaffirmed the need for developing rail defect detection systems that are more effective than those used today. One of the recent developments in rail inspection is the use of ultrasonic guided waves (UGWs) and non-contact probing techniques to target transverse-type defects. Besides the obvious advantages of non-contact probing, that include robustness and a potential for large inspection speed, such a system can theoretically detect transverse defects under horizontal shelling or head checks. This paper demonstrates the effectiveness of digital signal processing to enhance the damage detection sensitivity of the non-contact system. The method proposed here combines the advantages of UGW inspection with the outcomes of the Discrete Wavelet Transform (DWT) that is used for extracting robust defect-sensitive features. In particular, the DWT is exploited to de-noise the ultrasonic signals in real-time and generate a set of relevant wavelet coefficients to construct a uni-dimensional damage index. The general framework proposed in this paper is applied to the detection of crack-like and internal defects in a railroad track mock-up built at UCSD. The proposed signal analysis approach is general and is applicable to many other structural monitoring applications using UGWs as the main defect diagnosis tool. [ABSTRACT FROM AUTHOR]

Defects in rails caused by rolling contact fatigue (RCF) are of growing concern to the railway industry. Conventional ultrasonic inspection methods are often not reliable in detecting critical RCF defects. The aim of this work was to develop a reliable screening tool that discriminates between critical and tolerable defects and therefore complements the existing inspection methods. The method presented here employs ultrasonic surface waves which propagate several metres along the railhead. They are excited by a local immersion probe which is operated in pulse-echo mode and scanned along the rail; in practice this would be done using a wheel probe. The excitation frequency was chosen to be around 200 kHz at which there exists a suitable surface wave mode with a sufficient penetration depth. A spatial averaging technique is applied to suppress unwanted guided wave modes and reduce signal complexity. The method has been tested successfully on a number of specimens containing artificial and real defects. [ABSTRACT FROM AUTHOR]

Laser-Air Hybrid Ultrasonic Technique (LAHUT) combines laser generation with air-coupled detection of ultrasound. The technique is non-contact and has the characteristic of operating from remote distances. Acoustic wave lasergeneration apparatus can be metres away from the interrogated surface while air-coupled detection standoff can be on the order of several centimetres. The technique has the unique capability of interrogating structural materials in their true industrial environment. Dynamic tests are performed on parts with complex geometry, limited accessibility and curved surfaces. Also, dark and rough finish surfaces, which significantly reduce the efficiency of optical detection techniques, can be interrogated successfully. These characteristics make the LAHUT ideal for many industrial applications including the railroad industry. It was developed for railroad inspections targeting the most critical cracks in rails and wheels. State-of-the-art inspection techniques available to the railroad industry often miss Vertical Split Head (VVSH) and Transverse Detail Defect (TDD), which lie in unfavourable positions and orientations in the rail head. No method exists to perform dynamic inspections of the rail base or any part of the railroad wheel. Laboratory experiments were performed for the detection of TDD and Proof Of Concept (POC) field tests were performed for VSH, rail base cracks, thermal fatigue cracks along the wheel flange and tread and subsurface Shattered Rim Cracks (SRC) along the wheel tread. The results were successful and highly repeatable. The technique lends itself for digital collection and automated processing of data making the LAHUT a very strong candidate for next-generation railroad inspection tzechnique. [ABSTRACT FROM AUTHOR]

Abstract: Nowadays, efforts are being made by the railway industry for the application of reliability-based and risk-informed approaches to maintenance optimisation of railway infrastructures, with the aim of reducing the operation and maintenance expenditures while still assuring high safety standards. In particular, in this paper, we address the use of ultrasonic inspection cars and develop a methodology for the determination of an optimal strategy for their use. A model is developed to calculate the risks and costs associated with an inspection strategy, giving credit to the realistic issues of the rail failure process and including the actual inspection and maintenance procedures followed by the railway company. A multi-objective optimisation viewpoint is adopted in an effort to optimise inspection and maintenance procedures with respect to both economical and safety-related aspects. More precisely, the objective functions here considered are such to drive the search towards solutions characterized by low expenditures and low derailment probability. The optimisation is performed by means of a genetic algorithm. The work has been carried out within a study of the Norwegian National Rail Administration (Jernbaneverket). [Copyright &y& Elsevier]

A box test has been developed to simulate the effects of train loading and tamping on the performance of four different ballasts. The ballasts have each been loaded in the box by a simulated segment of sleeper for up to a million cycles of traffic loading, representing early life behaviour. Simulated tamping has also been performed on the ballasts causing rearrangement of grains. Results from the box tests have been found to be repeatable, and give realistic stiffness and settlement characteristics compared with full-scale tests on trackbeds in the UK. The performance of each of the four ballasts has been determined in terms of settlement characteristics, stiffness and degradation, and the results have been found to agree with results from Los Angeles abrasion tests and water absorption values, and also with petrographic analysis, thus demonstrating the usefulness of the box test for estimating the performance of ballast in the field. [ABSTRACT FROM AUTHOR]

Railroad track accident rates declined substantially since railroads underwent economic deregulation in 1980. This decline has been attributed to any of several factors including more stringent safety regulation, increased investment in physical plant, improved "safety culture" of firms, and improved technology. This article assesses the significance of these factors in the decline in railroad track accident rates for the period 1983-1994. The analysis applies a production function methodology commonly used to assess the productivity of public and private inputs in producing output. The analysis indicates that federal regulation during the 1983-1994 period, whether measured by defect rates, violation rates, or inspection rates, had a statistically insignificant affect on the rate of track accidents. Railroad track investment had a statistically significant affect on the decline in track accidents during the period. There were no statistically significant differences in the rate of change in track accident rates among firms given the level of other inputs. Lastly, while econometric considerations prevented direct testing for the impact of improved technology on the decline in track accidents, there was not a statistically significant acceleration or deceleration in the rate of technical change over the period. [ABSTRACT FROM AUTHOR]