Swamidas Punwani

Next Generation Locomotive Cab

This paper discusses the development of a user-centered control stand for the Federal Railroad Administration’s (FRA) Next Generation Locomotive Cab (NGLC) demonstration program. A “modified” Association of American Railroads (AAR) 105 side-mounted control stand was used as a starting point to facilitate bidirectional locomotive operation. Researchers applied a variety of qualitative human factor methods, including literature review, naturalistic observation, computer modeling, and heuristic evaluation, to design the improved control stand. The final design included a decluttered side control stand, a short desktop with three-panel front touchscreen displays that can accommodate and integrate current and future locomotive train technologies, and an overhead ceiling panel that replaces, in part, controls and displays traditionally located behind the engineer on the back wall. A mockup of the revised control stand design was fabricated as part of this program to demonstrate the human factors and ergonomic improvements. Researchers conducted structured interviews with locomotive engineers to validate the user-centered design approach. The engineers engaged in interactive scenarios that assessed the functionality of the workspace. The usability results provided the opportunity to improve upon the initial NGLC user-centered design. Changes included minor relocation of controls because they were in the reach path of other controls. Certain frequently accessed controls required relocation to more accessible locations. The LCD displays were redesigned with respect to information groupings and visibility issues. Feedback revealed that the transition from mechanical operations to electronic operations will result in the loss of auditory cues inherent in mechanical operations. The researchers suggest simulating auditory cues to promote personnel transition from mechanical to electronic operations. The results of this usability assessment identify the opportunity for future R&D cab integration efforts and demonstrate the importance of user-centered design and usability assessment in these efforts.Copyright

Feasibility of a Variable-Directivity Locomotive Horn

It is estimated that up to 9.3 million persons may be impacted by locomotive horn noise and up to 4.6 million of those may be severely impacted.1 In 2009, there were over 1,900 incidents, over 700 injuries and over 240 fatalities at highway-rail grade crossings.2 The National Academy of Engineering Committee on Technology for a Quieter America has indicated that the public would benefit if train warning horns were more directional and has recommended that research and development be undertaken to better understand the effects on safety and benefits to the public.3 A directive train horn has the potential to focus audible warning signals to desired locations including pedestrians and motorists at highway-rail grade crossings while minimizing noise to the surrounding community and employees in the locomotive cab.As a part of an ongoing Federal Railroad Administration (FRA)-sponsored research and development effort, the authors have examined the feasibility of and recommended an acoustical specification for an optimized train horn that would improve the detectability of the warning signal for motorists at critical positions along the crossing road while reducing the area of environmental noise impact. The detectability, noise impact area and occupational noise exposure have been compared for the optimized horn and several typical standard horns.Near the beginning of most sounding events (1/4-mile from the grade crossing) the optimized horn reduces noise exposure because a narrow beam of sound can be generated and focused at the grade-crossing. As the train approaches the crossing, the beam width must become wider. It is found that detectability could be improved and noise impact area reduced by up to 57%, but the optimized horn must have a directivity pattern and amplitude that dynamically changes as a function of train position relative to the crossing.Current acoustic source technologies which generate directive sound were examined including “acoustic hailing devices” (AHDs) which are recent technological advancements typically used for naval communications. Capable of focusing high amplitudes of sound within a narrow beam and dynamically changing the directivity pattern through electronic beam steering, AHDs have been identified as a feasible means of meeting the required specifications. A critical design issue for the optimized horn is controlling the directivity pattern at low frequencies. Development and testing of a prototype is in progress and actual improvements to detectability and reductions in noise impact will be analyzed. The paper briefly discusses the feasibility of the optimized horn and general information on cost and implementation.Copyright

Improving Crashworthiness of Railroad Rolling Stocks with New Generation Shock Energy Absorbers

This paper describes the results of quasi-static and dynamic tests of a new shock energy absorber (SEA) capable of high energy absorption while limiting peak dynamic force magnitude in the event of an impact or collision. The SEA utilizes the unique reversible phase transition behavior of Ultra High Molecular Weight Poly-Ethylene (UHMWPE) material under pressure. A prototype drop hammer test confirmed the device’s high energy absorption as well as high damping capabilities at a relatively high deformation rate. The results of the test were used to calibrate a finite element (FE) model that enabled scalability of the SEA for practical applications. Preliminary design and FE simulations were made under a Federal Railroad Administration (FRA) sponsored program toward using a set of SEA as a part of a crash energy management (CEM) system to improve locomotive crashworthiness. The main objective of the program was to prevent locomotive override in the event of an inline collision with a hopper car consist at a closing speed of 30 mph. The FE model, without CEM, was validated to a previously performed full-scale locomotive crashworthiness test at Transportation Technology Center, Inc. (TTCI), Pueblo. The FE simulation results with added CEM system showed successful prevention of locomotive override up to 32.1 mph collision speed. Further scope of using suitably tailored SEA units as buffers to the ends of passenger coaches and tank cars with the objective of enhancing their crashworthiness is discussed.Copyright

Computer Simulation and Validation of Fire Hazards in Fuel Tanks

Flammable materials such as gasoline, ethanol, and diesel fuel are commonly transported in bulk via rail. In many cases, pockets of vapor can be generated inside the tank that can present a hazard if spilled during a collision or other catastrophic accident. Vapor conditions above the Lower Explosive Limit (LEL) if exposed to an external ignition source can result in an explosion or fire. Alternately, residual vapors within a tank present an explosion hazard if not properly vented or inerted prior to maintenance activities. This paper summarizes a generalized study of hazards associated with flammable liquids using computation fluid dynamics (CFD) to predict vapor conditions within a tank or following a spill. The analysis was verified in laboratory testing using scaled tank geometries. A demonstration case was developed using diesel fuel in a locomotive fuel tank. Typical road locomotives carry 3000–5000 gal of diesel fuel during normal operation. As the locomotive consumes fuel, large volumes are available for vapor generation within the tank. In a post-collision scenario, under ambient temperatures over the flash point of the fuel, the vapor that vents to the atmosphere presents a significant fire hazard. Further, flammable mists can be generated by the sprays that develop due to fuel leaks from a moving train. Studies of accident cases over a 10 year period indicated that a fire occurred in 80% of the accidents in which fuel was spilled. A CFD analysis was applied to the geometry associated with a locomotive fuel tank. The analysis models the two phase flow using the “volume of fluid” formalism in Fluent, and using a user defined diesel fuel evaporation algorithm. The tank and environmental parameters included fuel volume, fuel temperature, and air flow within the tank, and critical values of vapor content, temperature and velocity were plotted. The analysis predicted ignition of the external vapor cloud at temperatures relevant to a spill in a summer environment in the southwest, and propagation of the flame into the fuel tank. Laboratory testing confirmed the analysis: Once ignited, a flame propagated into the tank, causing an explosion and fire. The analysis methods developed can be applied to a variety of geometries and fluids, providing a basis for full scale testing. The overall intent of the analysis is to aid in the development of fire mitigation approaches for fuel and flammable material transport that would be practical for railroad use.

A New Approach for Noise and Vibration Control in Locomotive Cabs

Noise and vibrations in locomotive cabs can significantly affect crew performance and cause long-term ailments, such as hearing loss, fatigue, and low back pain. Methods to reduce noise and vibrations have been implemented for the high frequency range but resulted in low frequency resonances. These resonances can exacerbate low frequency vibrations (<0.5 Hz), which can cause motion sickness. In addition, a tonal noise exists in the 50 to 200 Hz frequency range, which is more annoying than broadband noise, and which is not addressed in current noise reduction methods based on A-weighted noise metrics. To reduce vibration, the innovative approach proposed here will consider isolating only the floor of the cab rather than the whole cab as was previously reported in the literature. The isolation is achieved using nonlinear springs and dampers that provide isolation at high frequencies while avoiding resonances at low frequencies. The smaller inertia of the floor, controls, and crew, as compared to the entire cab, makes the necessary components much less expensive. To reduce the tonal noise in the range 50 to 200 Hz, active noise control is used in the vicinity of the crew seats. Analyses have shown that this new approach is very promising, and demonstrations are planned for mockups of locomotive cabs.Copyright

Innovative Design of Secondary Emergency Egress Systems for Railroad Locomotives

In a locomotive cab structural damage due to collision, derailment or rollover may often block the normal egress routes. These situations require suitable emergency egress systems that provide access both from interior by the crew and from exterior by the rescue team. After incorporation of a removable roof hatch as the primary egress system, a removable windshield and emergency hinge release of the rear door were selected as potential secondary emergency egress alternatives. Simple innovative concepts and cost-effective hardware systems have been developed at Foster-Miller laboratories and installed on mockup assemblies to provide viable solutions to the above two secondary egress systems. Proof of concept demonstration and functionality evaluation were successfully carried out. This paper presents the salient design features and functional evaluation of these novel emergency egress concepts. Feasibility of incorporating these secondary egress systems into new railroad locomotive cab design is briefly discussed.© 2004 ASME

Advances in the Railroad Locomotive Crashworthiness

The paper describes locomotive and fuel tank crashworthiness research being conducted by the Federal Railroad Administration for improved safety of the locomotive crew under collision scenarios. The research involves static and dynamic impact strength evaluations of locomotive structural components. These evaluations which are based on full scale tests and simulations using finite element analysis are described in this paper. Correlations between the test and simulation results are also presented in some cases.Copyright

Design of an Emergency Egress System for Locomotive Cabs

Improving the survivability of a locomotive crew in the event of an accident has been a concern of the Federal Railroad Administration in the past decade. Locomotive crashes can injure the crew as well as deform the locomotive cab. Exiting from a deformed cab can be difficult, particularly for injured crewmembers. Egress becomes an even greater challenge if the locomotive is toppled. From an initial list of emergency egress concepts, the following three were chosen for further development: 1) hand/footholds to aid climbing inside a toppled locomotive, 2) roof-mounted escape hatch, and 3) externally removable windshield. As the potential users of the egress system, train crews and emergency rescue workers were interviewed to provide feedback on the design concepts. Focus groups with locomotive engineers and conductors provided information about train crew perceptions of the three concepts. Interviews with rescue personnel provided a perspective on the concerns of emergency rescue operations. Based on the user feedback, the roof-mounted escape hatch with hand/footholds was selected as the preferred concept. Construction of a system mockup facilitated evaluation of this concept. The utility of the overall concept was evaluated using untrained personnel in the full-scale mockup of a toppled road locomotive cab. A preliminary examination of the cost implications of incorporating the hatch system into new locomotives indicated that the initial engineering costs, rather than the recurring manufacturing costs, are the issue. As such, the overall cost for implementing the hatch is likely to be low.Copyright

Progress in Railroad Freight Car Engineering

Every year the Rail Transportation Division (RTD), American Society of Mechanical Engineers (ASME) conducts a survey to document progress in the design, construction and use of freight cars and components. This paper describes the new developments. Some information was obtained from web sites. The industry continued to focus on the evolution of freight equipment in 2002 by adding flexibility and versatility to designs developed in the recent past. Due to a slow down in new car building fewer responses were received.Copyright