High Speed Trains (HST) face some of the most stringent requirements for ensuring passenger safety and comfort while operating at very high velocities. HST wireless communication systems therefore similarly require special considerations for network design, technology selection and system implementation. For infrastructure-based wireless communications, a handover occurs whenever a radio transitions from the coverage of the current base station to the next base station. The faster the train moves the shorter the time that it spends under coverage area before a handover is required. For HST this can be as short as 10–20 seconds. Furthermore, a HST moving at 220 mph experiences significant fast and small-scale wireless signal fading due to this velocity, but similarly may incur frequent connectivity losses due to the rapid transit across coverage areas. A route consisting of viaducts, bridges, tunnels or hilly regions drastically increases the need for rapid handovers since a large number of base stations are required to provide coverage and achieve acceptable Quality-of-Service (QoS) in such environments. Due to the relatively fixed amount of time needed to complete a handover, and the possibility of failed handovers, this reduces the usable time under coverage, and thus ensuring an optimal handover strategy selection is vital. Most of the routes span rural and suburban areas, which reinforces the need for a comprehensive network planning strategy, as these areas tend to be underdeveloped for cellular coverage. Given the complexity in available radio spectrum resources, detailed studies are required to aid in this technology selection process. However, with the predicted increase in the demand of railroad network data traffic generated by onboard sensors, onboard control and operation devices, passenger Internet services, etc., it becomes apparent that more resources are needed than are provided by current technologies such as LTE. Thus, including 5G New Radio for Railways (5G-NR2) in the consideration does not only provide railways a more cost-effective licensing option for frequencies, but also an opportunity to select the best possible radio access method for a given HST corridor. In this paper, we focus on the metrics related to handover and how they correlate with different radio access technologies for HST. Our results integrate the uncertainty of environmental factors to provide answers on technology selection driven by specific route, inter-site distances, and available bandwidth. Our wireless communication simulation results are driven by well recognized mathematical models that consider a variety of key parameters. The analysis of the handover performance will offer insights vital to future railroad network planning for multivariate radio access technologies, and to answer crucial questions about the potential for using frequency bands above 6 GHz in HST.

Railway track vertical alignment is an important indicator of serviceability condition and thus plays a critical role for maintenance planning. Estimating the rail profile through the vertical acceleration readings provides an efficient alternative to the current practice of optical methods using special vehicles. This paper proposes an algorithm to estimate the rail vertical profile using the vertical acceleration of the vehicle resulting from the train-track dynamic interaction. The algorithm is designed to approximate the inverse of the transfer function from the rail vertical roughness to the train’s measured acceleration. The approximation problem is formulated into an H-infinity optimal control design problem, which can be further transferred into a problem of convex optimization. The proposed algorithm possesses several advantages including easy design, little tuning effort, and low computational cost. In addition, to take into account the model uncertainty, an optimization-based learning framework is proposed to further enhance the performance of the proposed algorithm. The numerical study has been conducted comprehensively to validate the observer’s properties and effectiveness in reconstructing of the rail vertical roughness.

According to the Federal Railroad Administration (FRA) Highway-Rail Grade Crossing Accident/Incident database, more than 12,000 accidents occurred between 2012 and 2017 in the United States with casualties of around 3900. Despite repeated efforts to fully understand the risk factors that contribute to highway-rail grade crossing collisions, there still remain many uncertainties. A machine learning approach is proposed in this paper to find out significant factors, along with their individual impacts of crash severities at grade crossings. One of the most efficient and accurate machine learning algorithms, extreme gradient boosting (XGB or XGBoost), is applied to analyze 21 different accident and crossing -related characteristics per driver severities. The XGB model has been proven in previous studies across many research areas in transportation to outperform other machine learning-based methods and statistical classification methods, such as multinomial logit model, multiple additive regression trees, decision tree, and random forest, especially in prediction accuracy. Thereby, applying the algorithm is expected to provide highly reliable results to identify important factors that have impacts on injury severities at grade crossings. Such application will further aid the discovery of potential crossings with significant factors. The FRA’s Highway-Rail Grade Crossing Accident/Incident database from 2012 to 2017 is fused with the FRA Highway-Rail Crossing Inventory database for the analysis. Observations with missing information were removed from the original database. Crossing position under or over the railroad and pedestrian or other types of highway users were also not considered since they were not specifically of interest in this study. After the database cleaning process, it condensed to the total of 1,250 accidents out of the retrieved 12,630 from the combined database. The results show that adjacent highway traffic volume and train speed are the most significant factors causing accidents and injury severity. They are followed by the driver’s age and the estimated vehicle speed. It also indicated that truck-involved accidents and crossings with gates, flashing lights, and other types of warning devices combined, and highway user’s gender as a male also pertain to the higher injury rate. Through this study, it is possible to provide guidance to decision-makers in recognizing possible risks at-grade crossings that may cause driver casualties.

Tunnel fires are low-probability high-consequence events that could lead to loss of lives, property damage, and long service disruptions. The rapid rise of gas temperature in excess of 1000 °C within the confined tunnel space can affect the structural integrity of the tunnel. Although tunnel fires may not necessarily cause collapse, significant structural damage and disruption to rail services can lead to major economic losses. The objective of this paper is to investigate the expected structural damage in a cut-and-cover tunnel if exposed to a fire event. The analyses are completed by numerical simulations. In the first part of this work, the effects of fire scenario and variability in thermal properties of material, on the potential volume of damaged tunnel lining that would require repair are investigated. In case of tunnels, historical events show that limited accessibility to suppress the fire can cause the fire to burn for days. The fire scenarios considered in this work are defined based on (a) the worst-case envelop hydrocarbon fires such as the Rijswaterstaat (RWS) fire curve and the RABT ZTV fire curve, and (b) the potential heat release rates in railway tunnels. In the second part of this study, the effect of fire scenario on structural performance of a cut-and-cover tunnel is studied. The geometry and cross section of the Howard street tunnel in Baltimore that experienced a major fire in 2001 is used as the case study. The results show that the fire scenario and duration, while contains significant uncertainty, is one of the most influential factors on evaluating response of the tunnel structures.

The variations in the operation timetable or schedule of an electrified transit rail system can lead to substantial fluctuations in power demands of its traction power network. This paper studies the correlation between the maximum power demands and timetable perturbations for electrified transit rail systems. Specifically, the operation schedule uncertainties are quantified as two parameters: headway shift and headway perturbation. A computation algorithm is introduced to illustrate how to use these two parameters to obtain the worst case scenario to obtain maximum power demand of traction power substations. Also a special type of catenary-free light rail system is used as an example to illustrate the algorithm and numerical results.

Extensive research has been conducted by the research team in recent years to determine the prestressing steel and concrete properties that must be provided to ensure that the transfer length of a prestressed concrete railroad tie is shorter than the distance from the edge of the tie to the rail seat. In addition, a significant of amount of data has been collected that indicates high bonding stresses can produce longitudinal splitting cracks along the reinforcement. In a study of how prestressing steel and concrete properties relate to a ties propensity for longitudinal cracking, existing ties that have performed well in track for over 25 years without issues are being evaluated. One parameter of interest that affects the bonding stress is the amount of prestress force in a railroad tie, which is unknown for the existing ties being evaluated. The current paper focuses on a new method that was developed for determining the remaining prestress force in a tie. In a previous method for determining the prestress force, ties were first loaded in four-point bending to initiate flexural cracking. The crack opening displacement was measured in order to determine the applied load required to reopen the crack. Using this load and the cross-sectional parameters at the location of the crack, the prestress force in the tie can be calculated using static equilibrium. The issue with this method is that as a tie is being loaded and the crack propagates, there is a continuous change in the stiffness of the cross-section. This results in the load versus crack opening displacment curve being overly rounded. This increases the error when determining the load required to reopen the crack, and increases the uncertainty of the calculated prestress force. The new test method eliminates the problems associated with flexural testing by loading the ties longitudinally in tension. In the new proposed experimental method, ties that have been pre-cracked in the center are pulled in tension. Similar to the previous method, the crack opening displacement is measured while the tie is loaded. For the crack to fully open, the applied load must exceed the prestress force holding the crack closed. Prior to the crack opening, the applied load is resisted by the composite section of concrete and prestressing tendons. Once the crack as fully opened, the applied load is resisted by the prestessing tendons only. This creates two distinctly linear portions of the load versus crack opening displacement curve, one prior to the crack opening, and one after. The beginning of the linear portion post-crack opening marks a very clear upper bound for the amount of prestressing force in a tie. This method can estimate the remaining prestress force in a tie with much greater accuracy than the previous method, and eliminates the need of the cross-sectional parameters at the crack location. To verify this method, tests were first conducted on a smaller scale with prismatic beams with a known initial prestressing force. Then the method was applied to a full scale existing tie to determine the remaining prestress force. Results are presented for testing of both the prismatic beams, and the full scale tie.

Operational efficiency is one of the key performance indicators for all railroad systems. Infrastructure inspection and maintenance engineers are tasked with the responsibility of ensuring the reliability, availability, maintainability and safety of the railroad network. However, as rolling stock traffic density increases throughout the network, inspection and maintenance opportunities become less readily available. Inspection and maintenance activities normally take place at night, when there is little or no train movement to avoid disruption of normal railroad network operation. In addition, conventional inspection methodologies fail to deliver the efficiency required for the optimization of maintenance decisions, particularly with respect to track renewals, due to their defect detection sensitivity and level of resolution limitations. The fact that critical structural components such as rails and crossings (frogs) are randomly loaded increases the degree of uncertainty when trying to estimate their remaining service lifetime. Maintenance decisions are predominantly based on the feedback received from inspection engineers, coupled with empirical knowledge that has been gained over the years. The use of structural degradation models is too risky due to the uncertainty arising from the variable dynamic loads sustained by the rail track. The use of structural health monitoring techniques offers significant advantages over conventional approaches. First of all, it is non-intrusive and does not interrupt normal rail traffic operations. Secondly, defects can be detected and evaluated in real-time whilst their evolution can be monitored continuously, enabling maintenance to be scheduled in advance and at times where the need for rail network availability at the section concerned is at its lowest. This paper analyzes the potential risks and benefits of a gradual shift from traditional inspection approaches to advanced structural health monitoring techniques.

This paper presents the development and demonstration of an efficient reliability-based tool for the reinforced earth retaining wall design in heavy haul railway. Here, two major internal failure modes, rupture and pullout, are the focus in the demonstration. The First-Order Reliability Method (FORM) is adopted to estimate the probability of failure for each failure mode, and is implemented in a spreadsheet. The reliability analysis is conducted with the consideration of the effect of uncertainty in the reinforcement length, horizontal and vertical spacing between steel strips, tensile strength of steel strips as well as the material property of the backfills. Using this design tool, a few candidate designs can be easily obtained by meeting the acceptable probability of failure and the final design is determined based on cost. The results obtained using FORM are also verified by comparing with those from Monte Carlo simulation. This design tool is shown to be simple to use in the retaining wall design of the railway engineering.

Accurate unbiased assessment of transfer length for prestressed concrete railroad ties requires detailed knowledge of the longitudinal variation of geometrical cross-section parameters responsible for establishing the resulting surface strain profile. This is because the complex cross-sectional shape produces a non-uniform strain plateau region, which makes the accurate evaluation of transfer length more difficult. In particular, human judgment of a “plateau region” for assessment of the average maximum strain becomes subject to large uncertainty, and clearly this procedure cannot be used in any type of automated in-plant transfer length diagnostics. The important geometrical tie parameters include the cross-sectional area, centroid, moment of inertia, and the eccentricity of the prestressing wires. If a CAD drawing is available, this information can be digitally extracted from the CAD model representation of the crosstie. In fact, this digital extraction has been done and has already been in use for some time in assessing transfer length for one of the common crosstie manufacturer designs. However, current research efforts are investigating the characteristics of existing crossties which have been in track for many years, for which CAD drawings of the original designs are unlikely to be available. The objective of the current research is to develop a comprehensive understanding of the material characteristics that have caused splitting failures in prestressed concrete railroad ties, and those characteristics that have resulted in ties that have performed well after many years in track. As part of this effort, a three-dimensional (3D) Optical Scanning System is being used to accurately scan and quantify the surface geometry of previously manufactured ties that have been in service, so as to produce an accurate 3D CAD model for later analysis associated with the above long-term research objectives. For the initial phase of this work, a sample from the CXT crossties of known geometrical characteristics that were subjected to representative long-term loading at the TTCI Facility in Pueblo Colorado, was scanned so as to accurately map out detailed 3D tie surface geometry. These ties were cast using the same concrete materials but with different prestressing wires, and were all subjected to the same extreme in-track loading for a period of several years. A commercially-available 3D Laser-Based Optical Scanning System, having a maximum spatial resolution of approximately 0.1mm, was used to perform the surface scanning operations presented in this paper. The CXT tie provides a useful initial evaluation of the accuracy and general feature capture capability of the scanning procedure, since a 3D CAD model for this tie has been provided by the manufacturer. A detailed qualitative and quantitative analysis is presented which compares the 3D CXT CAD model geometry with the 3D geometry of the experimentally scanned ties. Illustrations as to how this 3D technique can reveal such features as abrasion and wear, along with the longitudinal variation of the above mentioned cross-section parameters associated with longitudinal surface strain and transfer length assessment, are included in this paper.

In current rail inspection processes, following a detection of a suspected internal defect, an additional secondary detailed inspection is required to (1) confirm the presence of the flaw and (2) determine the severity of the flaw to allow for optimal post-detection rail maintenance planning. Current ultrasonic devices in this secondary inspection efforts heavily rely the expertise and experience of the test personnel’s judgement to confirm the rail flaw and to characterize the internal defect by analyzing reflected waveforms. To eliminate the uncertainties in this secondary inspection process and to provide the testing operators with better defect characterization such as the size and location of the flaw, a defect ultrasonic imaging device utilizing synthetic aperture focusing (SAF) techniques is proposed in this paper. These imaging techniques have been successfully demonstrated in medical imaging, providing quantitative characterization of internal components, allowing for a better prognosis. Ultimately, having a quantitative evaluation of the internal flaw can lead to an increase in the safety of train operations by preventing derailments. Thus, in this paper, a preliminary portable rail defect imaging concept is proposed by the University of California, San Diego, to provide three dimensional images of internal defects in the rail. The prototype reconstructs a three-dimensional volumetric image of the rail, utilizing multiple two-dimensional planar ultrasonic images. Improvements to the conventional tomographic imaging algorithms have been made by utilizing a mode-selective image reconstruction scheme that exploits the specific displacement field, respectively, of the longitudinal wave modes and the shear wave modes, both propagating simultaneously in the test volume. The specific mode structure is exploited by an adaptive weight assignment to the ultrasonic tomographic array. Such adaptive weighting forces the imaging array to look at a specific scan direction and better focus the imaging onto the actual flaw (ultrasound reflector). This preliminary study shows that the usages of the adaptive weights based on wave structure improves image dynamic range and spatial resolution, when compared to a conventional ultrasonic imaging technique such as Delay-And-Sum (DAS). Results will be shown both from numerical models and experimental tests of internal flaws in rails.

Freight rail cars may experience high input forces during a coupling event, which could potentially cause damage to the car body and/or lading. The AAR recommended practice states that cars should not be coupled at speeds greater than 4 mph. However, this recommendation is not always followed and cars are often coupled at much higher speeds. As a result, accelerometers on the car body are sometimes used to monitor impact events. Threshold levels may be set to determine if an over-speed or high-force impact event has occurred. However, a single acceleration value can be difficult to interpret because its relationship to impact force is dependent on many factors, including car type, end-of-car device type, lading type, and loading condition. Dynamic modeling and parametric studies may be used to determine these relationships which can be applied in practice. This paper presents a study on the relationship between struck coupler force and car body acceleration for a series of impacts on a tank car in both loaded and unloaded states. For the loaded condition, the tank was filled with water. The simplest change from an unloaded tank to a loaded tank is the decrease in acceleration for a given force due to the added mass. However, there is additional complexity added to the system due to the sloshing liquid inside the tank. When attempting to model this dynamic system there is added uncertainty in struck coupler force estimation because of the non-linearity in low frequency car body oscillations. Several example data sets are presented in the time and frequency domains to illustrate this point. The data is then used to generate an empirical model using system identification techniques. The results show that the proposed model offers improved characterization of the system as compared to conventional techniques by accounting for the uncertainties introduced by the sloshing liquid in the tank. The proposed technique is computationally efficient and can potentially be implemented in real time. The model is used to estimate struck coupler force and is validated with real data.

Automated in-plant diagnostic testing of prestressed concrete railroad crossties is now within reach due to recent progress in robust surface strain measurement techniques. The newly developed non-contact Laser Speckle Imaging (LSI) technique has been shown to provide rapid and accurate surface strain profile measurement, which is a key requirement for rapid transfer length assessment. Accurate determination of transfer length is critical for maintaining continuous production quality in the modern manufacture of prestressed concrete railroad crossties. Conventional assessment of transfer length generally presumes the underlying existence of a bilinear prestressing force distribution and a corresponding bilinear surface strain profile. Furthermore, it is well-known that this bilinear profile is smoothed due to the effects of finite gauge length during the process of measuring surface strain. In addition, recent extensive crosstie measurements in concrete railroad tie plants have shown significant departures from this simple bilinear profile, which bring to question the general validity and reliability of the traditional 95% AMS (95% Average Maximum Strain) method. Deviations from the simple bilinear profile shape were shown to be partially due to the non-prismatic shape of typical concrete railroad ties. In addition, extensive comparisons between predicted and measured surface strain profiles on numerous crossties suggest that the underlying strain distribution for crossties is best represented by an exponential strain profile, with an asymptotic approach to the fully-developed compressive strain. This is in contrast with extensive testing of prisms with fixed cross-section and fixed prestressing wire eccentricity, for which the surface strain appears to be best represented by the simple bilinear strain profile. Clearly, departures from non-prismatic behavior have added complexity to transfer length measurement. If accurate and reliable measurements of this important quality control parameter are to be realized, these issues of transfer length uncertainty need to be addressed. This paper provides an experimental comparison of several possible alternative transfer length assessment procedures, in an attempt to answer important uncertainty questions which need to be addressed if rapid real-time transfer length is to be achieved. It is shown that in spite of considerable differences in the transfer length processing methods, and significant departures from prismatic behavior, the averaged results are in many cases consistent with the simple bilinear underlying strain profile assumption. Bias in the measurement of crosstie transfer length due to non-prismatic behavior will also be investigated in this paper.

This paper describes a numerical procedure to examine the holding forces needed to secure a cut of railroad tank cars staged on a grade during loading and unloading operations. Holding forces are created by applying emergency brake systems and blocking (or chocking) wheels. Moreover, the holding force to secure the cut of cars must be greater than or equal to the gravitational component of force acting on the cars that is parallel to the grade. Engineering statics are applied to examine the forces acting on the individual cars resting on an inclined plane. An equation to calculate holding force is developed that includes two types of factors: constants (i.e. nonrandom or deterministic factors) and probabilistic variables (i.e. factors with inherent uncertainty or randomness). The numerical procedure applies Monte Carlo simulation techniques to study the uncertainties in the engineering analysis. The Monte Carlo approach is well suited to study the uncertainties and inherent variability associated with some of these factors. The factors assumed to be deterministic in this procedure are: steepness of the grade, total number of cars on the grade, number of cars with hand brakes applied, number of chocked wheels, and weight of the tank cars. The factors treated as random variables are: tension in the hand brake chain, mechanical efficiency in the linkages of the brake system, coefficient of friction between the brake pad and the wheel, and the coefficient of friction between the chocks and the rail. Probability distributions are assumed for each of the random variables. In addition, a probabilistic sensitivity analysis is conducted to examine the relative effect of the random variables on the reliability of the braking system to secure the cut of tank cars on a grade.

To adequately satisfy the demands placed on North America’s railway infrastructure through ever increasing freight tonnages and development of its high speed rail program, the design and performance of concrete ties and elastic fastening systems must be improved. As a part of a study funded by the Federal Railroad Administration (FRA) aimed at improving concrete crossties and fastening systems, field experimentation was performed at the Transportation Technology Center (TTC) in Pueblo, CO by researchers from the University of Illinois at Urbana-Champaign (UIUC). This paper details the extensive instrumentation program which includes strain gages and linear potentiometers. Testing was conducted over seven adjacent concrete crossties in tangent and curve track utilizing TTC’s Track Loading Vehicle (TLV) as well as passenger and freight train consists. Measurements taken consisted of the wheel-rail input loads, component stresses (e.g. insulator post compression), concrete tie strains, and displacements of the rail and concrete tie. The data was collected synchronously to provide a means to capture the load path, target areas of uncertainty, and provide comprehensive data for the validation of a multi-tie, 3-D finite element model being developed by UIUC. Varying train speeds, track curvature, and loading types provided a means to assess the loading variability that can be expected within the fastening system and lead to more purposeful and efficient instrumentation strategies. Furthermore, this data can be used to guide future research in further quantifying the field loading demands on system components, ultimately leading to the mechanistic design of the concrete crosstie and fastening system.

This paper presents the research framework and preliminary findings from a recently started Federal Railroad Administration (FRA) sponsored research project at the University of Illinois at Urbana-Champaign on developing and using seismic wave propagation principles to develop a track substructure (ballast and subgrade) condition assessment system. This condition assessment system will be used to evaluate track safety and to predict inspection intervals. This research is needed because there is no tool or system available that quantitatively measures the mechanics based properties of the layers comprising a track system. These mechanics based properties are shear modulus, modulus of deformation (Young’s modulus), and shear strength that can be derived from direct measurement of the shear wave velocity profile. Currently the modulus and shear strength of the track system materials are usually estimated which leads to uncertainty in the numerical analyses and estimates of track safety.

Railroad signaling systems are a vital part of the national railroad that detect trains on the track, identify track fractures, prevent derailments, and alert signal crossing stations when a train approaches. Failures in the signal wire attachments (studs) to rail create uncertainty in the system resulting in reduced train speeds, additional inspection and reinstallation costs, which translate into train delays, downtime, lost productivity and lost profitability for the railroads. Current methods of attaching studs to rails appear to exceed the critical (phase transformation) temperature in the rail material. There have been cases where this has resulted in formation of martensite in the stud-to-rail bond area during cooling. A brittle phase like martensite can produce fractures when stress is applied. Additionally, liquid metal embrittlement has been found in weld joints that involve the use of a brazing compound or solder to attach a signal wire. Methods that involve drilling for a plug attachment through the neutral axis of the rail result in decreased but acceptable fatigue performance. In an effort to avoid damage to the rail, studs have been moved from their ideal location (on the side of the rail head) to the middle of the web, close to or at the rail neutral axis. However, this location for studs causes other problems — wires and studs are highly prone to interfere with maintenance-of-way equipment. Under funding from the Federal Railroad Administration, EWI has developed and patented an inertia friction welding (IFW) process that is a field-portable, repeatable, and reliable solution for signal-wire attachments; in addition, the solid-state bonding mechanism provides advantages over the existing bonding solutions. IFW is used to weld a stud of dissimilar metal to rail, which in turn allows a signal wire to be connected. Several weld stud alloys were chosen for process feasibility trials. These trials identified parameters that produced solid-state welds between the stud and rail with no martensite at or near the bond line. Further experimental trials were conducted to define a range for rotational speed and welding thrust load. Repeatability testing was also conducted to ensure that there is no evidence of martensite at or near the bond line after multiple stud weld-remove-and-repair cycles. A conceptual design of a field-portable rail inertia welder, based on EWI’s patented portable inertia welding technology, has been completed. The welder is lightweight and capable of being powered by a small electric motor. Internal timing and process controls can maintain and deliver weld quality. The simplicity of the process will yield consistent joint performance with minimal operator training and a variety of environmental conditions. Research is being conducted to examine the reliability of the process through a series of bending fatigue tests, corrosion tests and in service testing.

Locomotive planning has been a popular application of classical optimization models for decades, but with very few success stories. There are a host of complex rules governing how locomotives should be used. In addition, it is necessary to simultaneously manage locomotive inventories by balancing the need for holding power against the need for power at other yards. At the same time, we have to plan the need to return foreign power, and move power to maintenance facilities for scheduled FRA appointments. An additional complication arises as a result of the high level of uncertainty in transit times and delays due to yard processing, and as a result we may have to plan additional inventories in order to move outbound trains on time despite inbound delays. We describe a novel modeling and algorithmic strategy known as approximate dynamic programming, which can also be described as a form of “optimizing simulator” which uses feedback learning to plan locomotive movements in a way that closely mimics how humans plan real-world operations. This strategy can be used for strategic and tactical planning, and can also be adapted to real-time operations. We describe the strategy, and summarize experiences at Norfolk Southern with a strategic planning system.

United States (US) Freight and Passenger railroads and transit entities are preparing for the deployment of Positive Train Control (PTC) systems as soon as the end of 2012, and by Federal mandate, by the end of 2015. PTC depends on a reliable and robust wireless data link between train and wayside equipment, train and network access points, and waysides and network access points. While, for the wireless component, some spectrum has been acquired and initial functionality defined, there will be lessons learned and new expectations as systems are rolled out over this period and beyond. Since the average service life of radio equipment in rail and transit applications is in excess of 10–15 years, and a system design may remain in place for 20–25 years, the challenge is to ensure that wireless systems are flexible enough to adapt to technology changes that may occur during the radio system’s long service life. Software-Defined Radio (SDR) is the appropriate approach to deal with this future uncertainty. The worldwide cellular communications standards are a great example: 3GPP established its first 3G specification, Release-99, in the year 2000; there have been 7 full specification releases since then, demonstrating the challenges of predicting future use based on current expectation. Deployment and long-term maintenance account for the majority of system cost: when system deployment is expensive and time-consuming, the needs for flexible design are crucial. The maintenance cost should be added and weighted higher in the calculation for total cost of ownership. One can argue that fixed design is cheaper; however, the total cost of ownership may end up much higher when changes are needed before the end of the product’s expected service life. In Information Technology, the system performance doubles approximately every 18–24 months. Thoughtful radio design can leverage this generational improvement. To address the issue of broad interoperability and a forward-looking specification, radio experts, including transit systems integrators, Federal agencies, end device and chipset manufacturers, and researchers, from around the world have teamed up under the aegis of the Institute of Electrical and Electronic Engineers (IEEE) to establish a Positive Train Control group for the RF/PHY/MAC based upon the well adopted IEEE 802.15.4 standard. The outcome of this effort will ensure the maturity of a PTC specification and long term maintenance of this mission-critical PTC wireless interface protocol. With any new specification development, continuous vetting, modification and upgrade will occur over coming years to improve the functionality and stability. SDR architectures allow the radio system to follow the standard. SDR allows railroads to start system validation and hardware qualification now, in order to meet the required Federal deadline. Since SDR provides a continuous path for interoperability as radios can reprogram and reconfigure on the fly, the hardware can remain unchanged while interoperability and advances in standards can be met through software upgrade.

Internal rail flaws continue to present a significant issue for the railroad industry. Current practices to mitigate the risk of catastrophic failure of the rails involve inspection for internal flaws and cracks using ultrasonic rail flaw detector technology, usually employed on rail-based vehicles. Following the identification of a suspected defect by an inspection vehicle, a detailed inspection of the suspect area is usually conducted to confirm the presence of the defect prior to the remedial action. Current portable or ultrasonic devices require significant expertise to allow test personnel to make a good judgment regarding the presence and severity of the flaw. A new generation of handheld detector is being developed to provide accurate three-dimensional images of the suspected flaw, thereby eliminating uncertainties in the inspection and providing operators with accurate sizing and orientation information. This paper presents a prototype ultrasonic handheld rail flaw inspection device designed and developed through support provided by the Federal Railroad Administration’s Office of Research and Development by ENSCO, Inc., which can produce accurate three-dimensional images of suspected flaws for verification and characterization proposes.