Cambridge, MA, United States
Cambridge, MA, United States

Volpe, The National Transportation Systems Center or simply Volpe in Cambridge, Massachusetts, is a center of transportation and logistics expertise, operating under the United States Department of Transportation .The Volpe Center is named after Massachusetts Governor and U.S. Secretary of Transportation John Volpe, and its work includes a broad mix of projects that cut across traditional transportation modes and technical disciplines including the Federal Aviation Administration's Enhanced Traffic Management System and Safety Performance Analysis System , and the Federal Motor Carrier Safety Administration's SafeStat Online.The Center assists federal, state, and local governments, industry, and academia in a number of areas of consultation including human factors research, system design, implementation and assessment, global tracking, strategic investment and resource allocation, environmental preservation, and organizational effectiveness.Volpe is part of the U.S. DOT's Research and Innovative Technology Administration. However, it differs from most federal organizations in that it receives no direct appropriation from Congress. Instead, it is funded 100% through a fee-for-service structure in which all costs are covered by sponsored project work . Wikipedia.

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Yu H.L.,MacroSys Research and Technology LLC | Jeong D.Y.,Volpe National Transportation Systems Center
Theoretical and Applied Fracture Mechanics | Year: 2010

Nonlinear dynamic finite element analysis (FEA) is conducted to simulate the fracture of unnotched Charpy specimens of steel under pendulum impact loading by a dedicated, oversized and nonstandard Bulk Fracture Charpy Machine (BFCM). The impact energy needed to fracture an unnotched Charpy specimen in a BFCM test can be two orders of magnitude higher than the typical impact energy of a Charpy V-notch specimen. To predict material failure, a phenomenological, stress triaxiality dependent fracture initiation criterion and a fracture evolution law in the form of strain softening are incorporated in the constitutive relations. The BFCM impact energy results obtained from the FEA simulations compare favorably with the corresponding experimental data. In particular, the FEA predicts accurately the correlations of the BFCM impact energy with such factors as specimen geometry, impactor tup width and material type. The analyses show that a specimen's progressive deterioration through the thickness dimension displays a range of shear to ductile fracture modes, demonstrating the necessity of applying a stress state dependent fracture initiation criterion. Modeling the strain softening behavior helps to capture the residual load carrying capability of a ductile metal or alloy beyond the onset of damage. The total impact energy can be significantly under predicted if a softening branch is not included in the stress-strain curve. This research supports a study of the puncture failure of railroad tank cars under dynamic impact loading. Applications of the presented fracture model in failure analyses of other structures are further discussed. © 2010.

Lewis K.C.,Volpe National Transportation Systems Center | Porter R.D.,Environmental Law Institute
Ecological Monographs | Year: 2014

Biofuels are being pursued for their potential greenhouse gas (GHG) emissions benefits, among other reasons. In order to maximize productivity, avoid food-fuel conflicts, and minimize GHG emissions, many advanced biofuel feedstock crops, such as those desired by the aviation community, are under consideration based on traits, such as high biomass and/ or seed production, tolerance of marginal cultivation conditions, and short generation times, that may also be predictors of potential invasiveness risk. Biofuel-related invasion risks can be mitigated through careful feedstock crop selection and cultivation techniques developed from the invasion science literature. Existing voluntary best practices and some state and federal regulatory requirements in the United States recommend and/or require the use of such risk mitigation strategies. However, other policies and programs allow or provide incentives for biofuel production without conditions requiring the use of these strategies. We have synthesized information on the scientific knowledge of invasive species predictors and their use (or absence) in voluntary codes and U.S. regulatory frameworks and incentive programs. We highlight the existing tools and approaches for assessing invasion risk and avoiding the introduction and spread of invasive species as a result of biofuel feedstock cultivation. A wellcoordinated combination of species restrictions, biosecurity requirements, and incentives for selection of less risky biofuel crops may effectively balance the desire for increased biofuel production while minimizing invasion risk. © 2014 by the Ecological Society of America.

Noel G.J.,Volpe National Transportation Systems Center
Proceedings of the Air and Waste Management Association's Annual Conference and Exhibition, AWMA | Year: 2015

The methodology for modeling ground based mobile sources at airports using the Federal Aviation Administration's Aviation Environmental Design Tool Version 2b and the EPA's Motor Vehicle Emissions Simulator (MOVES) is presented. Ground based mobile sources include roadways and parking facilities on or in the vicinity of an airport property. The MOVES runs for airport analyses must include all the vehicle and types fuel types, e.g., gasoline, diesel, CNG, that the analyst wants to model in the project area. Pollutant and emissions processes for roadway links, including HC, VOC, SO2, and PM, are also presented. This is an abstract of a paper presented at the 108th AWMA Annual Conference and Exhibition (Raleigh, NC 6/22-25/2015).

Smith S.,Volpe National Transportation Systems Center | Razo M.,Volpe National Transportation Systems Center
Journal of Intelligent Transportation Systems: Technology, Planning, and Operations | Year: 2016

The Connected Vehicle Safety Pilot Model Deployment is a major test of safety applications that are based on vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) dedicated short range communications (DSRC). Approximately 3000 vehicles in a mid-sized city (Ann Arbor, MI) will be equipped with devices in order to assess safety benefits in a naturalistic environment. To ensure that sufficient data are collected, participants will be chosen so that their vehicles will interact frequently with each other and with the roadside equipment. Since the 3000 vehicles are a small fraction of all vehicles in the city, choosing a deployment strategy requires careful analysis of the network and traffic flows. This research describes the development of a regional traffic microsimulation model that was used to estimate the number and spatial/temporal locations of V2V interactions under various deployment strategies. Steps taken to develop the model included the following: (a) converted the existing network planning model for the Ann Arbor area to a regional microsimulation model, (b) developed a method to identify the numbers, origins, and destinations of trips using equipped vehicles, and (c) developed postprocessing code to track all equipped vehicles from the second-by-second microsimulation vehicle snapshot data and to identify interactions between equipped vehicles. This interaction information was integrated with available Integrated Vehicle-Based Safety Systems (IVBSS) data to estimate the potential number of conflicts among equipped vehicles. The resulting model was used to assess various safety deployment scenarios in a field operational test. © This article not subject to U.S. copyright law.

Yu H.,Volpe National Transportation Systems Center | Jeong D.Y.,Volpe National Transportation Systems Center
International Journal of Impact Engineering | Year: 2016

This paper presents a computational framework that analyzes the effect of fluid-structure interaction (FSI) on the impact dynamics and puncture failure of pressurized commodity tank cars carrying hazardous materials. Shell (side) impact tests have been conducted on full scale tank cars resulting in deformed or punctured tank cars. A finite element (FE) modeling method is applied that explicitly simulates the three distinct phases in a tank car loaded with a liquefied substance: pressurized gas, pressurized liquid and solid structure. Furthermore, an equivalent plastic strain based fracture initiation criterion expressed as a function of stress triaxiality is adopted to depict the fracture behavior of the tank car steel material. The fracture initiation is implemented for ductile, shear and mixed fracture modes and followed by further material deterioration governed by a strain softening law. The force, displacement and impact energy results obtained from the FE analysis show good agreement with the corresponding shell impact test data. The simulations demonstrate that FSI plays a critical role in predicting the correct dynamics of tank car impact. The puncture resistance of a tank car, characterized as limit impact conditions in terms of puncture energy or puncture velocity, is further analyzed in shell impact scenarios. The puncture energy is shown to increase as the initial fluid pressure decreases, the tank car thickness increases or the effective impactor size increases. Quantitative correlations between puncture energy/velocity and each of these factors are obtained using the FE analysis method developed in this paper. © 2015 Published by Elsevier Ltd.

Hastings A.L.,Volpe National Transportation Systems Center
INTER-NOISE 2015 - 44th International Congress and Exposition on Noise Control Engineering | Year: 2015

Auralization of moving sources provides a practical method to generate large and varied stimuli sets that can be used to help one understand the implications of specific sound generation parameters for human subject experiments and for public outreach. A practical approach is described that includes free field propagation, Doppler shifting via interpolation of the time-delayed source signal, and localization through the use of discrete head-related transfer functions with weighted averaging to produce continuous changes in position. The approach assumes a stationary receiver but makes no assumptions on the trajectory of the source. The method is sufficiently straightforward and abstract to allow easy extension, and simulation times are short enough for extensive experimentation. © 2015 by ASME.

Yu H.,Volpe National Transportation Systems Center | Jeong D.Y.,Volpe National Transportation Systems Center
Structures Congress 2014 - Proceedings of the 2014 Structures Congress | Year: 2014

Pretensioned concrete ties are increasingly employed in railroad high speed and heavy haul applications. The bond between prestressing wires or strands and concrete plays an important role in determining the transfer length of pretensioned concrete members, but little research was done to characterize the transfer length in terms of steel reinforcement and concrete factors for railroad concrete ties. The Federal Railroad Administration is sponsoring a comprehensive test program at Kansas State University (KSU) aimed at quantitatively correlating prestressing steel and concrete variables with the transfer length of pretensioned concrete crossties. The Volpe Center has been applying the data obtained in the KSU test program to develop bond models that can be used in transfer length prediction and failure analysis of concrete ties. This paper describes finite element (FE) model development related to the smooth prestressing wire whose dominant bonding mechanisms with concrete are chemical adhesion and friction. The commercial FE software, Abaqus, is employed, and the steel-concrete interface is discretized with cohesive elements. A user bond model is developed within the elastoplastic framework and implemented for axisymmetric and 3D cohesive elements. The bond model defines constitutive relations in terms of normal and shear stresses vs. interfacial dilation and slips. The bond behavior is initially linear elastic, followed by adhesion and friction that are governed by a yield function and a plastic flow rule specific for the smooth wire-concrete interface. The main bond material parameters are normal and shear elastic stiffness, initial adhesive strength, plastic slip at which adhesion first breaks completely, and coefficient of friction. Except for the coefficient of friction, which is determined with reference to the open literature, the bond parameters are calibrated from untensioned pullout tests and pretensioned prism tests conducted at KSU. The calibrated bond parameters exhibit a dependence on the nominal compressive strength of concrete at the time of pretension release. Because considerable concrete creeping has been observed in the periods between pretension release and concrete strain measurement in the test program, an additional concrete material parameter, basic creep compliance, can be calculated and applied to adjust the concrete surface strain data. The user bond model is then validated with transfer length data measured on actual concrete crossties made with a smooth prestressing wire in a tie manufacturing plant. © 2014 American Society of Civil Engineers.

Tyrell D.,Volpe National Transportation Systems Center
2015 Joint Rail Conference, JRC 2015 | Year: 2015

Research is being conducted to develop technical information needed to formulate effective natural gas fuel tender crashworthiness standards. This research is being performed for the Federal Railroad Administration's (FRA's) Office of Research, Development, and Technology, and intended to facilitate industry efforts to use natural gas as a locomotive fuel. Strategies to assure crashworthiness during moderate accidents, such as train-to-train collisions at speeds up to 40 mph, are being evaluated. This research applies the approach FRA has used to develop technical information on locomotive, hazmat tank car, and diesel fuel tank crashworthiness. There are four primary tasks: 1. Definition of collision scenarios 2. Evaluation of traditional designs 3. Evaluation of alternative designs 4. Recommendation of effective crashworthiness strategies The tender scenarios have been drafted from reviews of freight train accidents and of scenarios developed for locomotives, hazmat tank cars, and fuel tanks. From these reviews, five scenarios were selected. These scenarios are intended to bound the range of collisions that a tender may experience, are being used to evaluate the crashworthiness of traditional tender designs, and will be used to evaluate alternative design tenders. The five candidate scenarios are: 1. Train-to-train collision 2. Grade-crossing accident 3. Tender derailment and rollover 4. Impact into tender tank shell during derailment 5. Impact into tender tank head during derailment As part of previous research on locomotives and passenger equipment, a range of crashworthiness analysis techniques were developed. These include simplified techniques, which can be performed rapidly and provide essential results, and detailed computer simulations which provide a wealth of information. The crashworthiness performance of a hypothetical tender design has been evaluated using simplified techniques. Simplified techniques include quasi-static crush analysis of structural elements and lumped-parameter analysis of train dynamics. The results suggest that efforts to enhance crashworthiness should principally be directed toward the trainto-train scenario. Work is ongoing to develop strategies for improving tender crashworthiness. This research is being conducted cooperatively with the Association of American Railroads (AAR). The research results are being shared with the AAR's Natural Gas Fuel Tender Technical Advisory Group (NGFT TAG). The NGFT TAG is developing industry standards, including crashworthiness requirements, for revenue-service natural gas fuel tenders. There is a companion paper which describes crashworthiness research sponsored by AAR, including detailed computer simulations of tender crashworthiness. This paper describes development of scenarios and simplified analyses of tender crashworthiness.

Llana P.,Volpe National Transportation Systems Center
2015 Joint Rail Conference, JRC 2015 | Year: 2015

The Office of Research, Development, and Technology of the Federal Railroad Administration (FRA) and the Volpe Center are continuing to evaluate new technologies for increasing the safety of passengers and operators in rail equipment. The results of vehicle-to-vehicle override, where the strong underframe of one vehicle, typically a locomotive, impacts the weaker superstructure of the other vehicle, can be devastating. Crashworthy components which can be integrated into the end structure of a locomotive have been developed to inhibit override in the event of collision. Recent research has resulted in the development of a design concept, including evaluation with finite-element analysis (FEA), fabrication, and component tests. The design concept developed incorporates two key components: a push-back coupler and a deformable anti-climber. Detailed designs for these components were developed and the performance of the designs was evaluated through large deformation dynamic FEA. Test articles were fabricated and dynamically tested to verify their individual performance characteristics. The tests were successful in demonstrating the required performance of the components. Test results were consistent with finite element model predictions of energy absorption capability, force-displacement behavior, and modes of deformation. Work is ongoing to retrofit these crashworthy components onto conventional locomotives and conduct full-scale dynamic impact tests of colliding cars, as well as colliding trains. Service tests will be performed to measure the impact speed at which push-back coupler triggering occurs. Vehicle-to-vehicle tests will be conducted to demonstrate the performance of the crashworthy components working together as an integrated system. The vehicle-to-vehicle tests will also allow an evaluation of the crashworthiness compatibility of a modified locomotive with a range of equipment, including conventional locomotives, cab cars, and freight cars. Train-to-train tests are planned to demonstrate incremental improvement, increased crashworthiness, compatibility, and serviceability. This paper describes the tests that are planned to demonstrate the behavior of these components when they are integrated into the end structure of a locomotive. The tests will demonstrate the in-service and crashworthiness performance of the modified locomotives. This research program endeavors to advance locomotive crashworthiness technology and develop the technical basis for generating specifications for push-back couplers and deformable anti-climbers.

Van Eikema Hommes Q.,Volpe National Transportation Systems Center
SAE Technical Papers | Year: 2012

ISO 26262 is the first comprehensive automotive safety standard that addresses the safety of the growing number of electric/electronic and software intensive features in today's road vehicles. This paper assesses the standard's ability to provide safety assurance. The strengths of the standard are: (1) emphasizing safety management and safety culture; (2) prescribing a system engineering development process; (3) setting up a framework for hazard elimination early in the design process; (4) disassociating system safety risk assessment from component probabilistic failure rate. The third and fourth strengths are noteworthy departure from the philosophy of IEC61508. This standard has taken much-needed and very positive steps towards ensuring the functional safety of the modern road vehicles. SAE publications from industry show a lot of enthusiasm towards this standard. This paper suggested a number of items to be considered further strengthen the standard's ability to provide safety assurance. First, the Automotive Safety Integrity Level (ASIL) assessment may want to consider only the severity level, so that the subjectivity involved in likelihood assessment is eliminated. The ASIL assessment also needs to be standardized across manufacturers in order to address the tension between safety and business competitiveness. Government, industry consortium, and research institutions may want to work together on ASIL standardization efforts. Second, this standard provides little guidance on how to eliminate hazards in the design, but rather provides details on how to design and evaluate the effectiveness of component failure detection and control mechanisms. This paper identifies research that could be conducted on how to adapt the System Theoretic Accident Modeling and Process model during the design phase. Third, this standard gives detailed guidance on reliability engineering methods for component failures, but little on system safety design methods. Reliability and safety are different attributes of the system. This standard can be improved by further research on adapting system safety engineering methods to this standard. Fourth, the standard also substitutes good software systems engineering practices for software safety, although this is on par with other industry standards. Further research is needed to address software safety assurance. Fifth, the need for more detail in the safety assurance process and plan for product and operation phases of the product are discussed. Last, the needs for better design methods and safety assurance plan concerning driver/vehicle interaction design are also presented.

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