Developing Guidelines for Crashworthiness of Light Rail Vehicles in Mixed Fleet Operations

Abstract

As new passenger rail cars are introduced into existing rail fleets, the potential structural for incompatibility between cars in a collision is a safety concern. Crush damage that occurs when dissimilar strength vehicles collide is concentrated in the weaker vehicle. In a serious collision the deformation of the weaker vehicle could be sufficiently large to intrude into the occupied volume of the operator or passenger compartments. As a result, the strength incompatibility has the potential for increased risk of injury for passengers in the weaker vehicle. The design strategy of many modern rail vehicles is to reduce vehicle weight and incorporate crashworthiness design features to improve safety. This is in contrast to an older design approach where strength requirements, such as a high buff strength, were included to ensure structural integrity. The objective of this study is to assess the collision risk for a mixed rail fleet of different vehicle designs. Collision safety is investigated for three different vehicle types. The crash scenarios investigated include vehicle to vehicle collisions between newly designed cars, between older designed cars, and between a mix of new and old designs. To quantify risk, parameters such as cab crush strength, occupant volume strength, and collision speed are varied in computer crash simulations to uncover potential safety problems associated with mixed car operation. Results from these parametric analyses are presented and utilized to guide the development of new crashworthiness specifications for mixed fleet operation.

Developing CEM design standards to improve light rail vehicle crashworthiness

“…In a contrary fashion, some structures may harden at such a high rate once collapse begins that minimal energy is absorbed and deceleration of the light rail vehicle occupants is severe [8]. Figure 2 illustrates the concepts of structural softening and hardening [8]. Application of a prescriptive metric such as th static strength without specification of the de behavior is a shortcoming of this approach.…”

“…Structural behavior can be unpredictable and in some cases the crush load after initial collapse drops in magnitude, potentially leading to rapid structural collapse of the operator compartment or the passenger compartment. In a contrary fashion, some structures may harden at such a high rate once collapse begins that minimal energy is absorbed and deceleration of the light rail vehicle occupants is severe [8]. Figure 2 illustrates the concepts of structural softening and hardening [8].…”

“…Dynamic simulation and testing of vehicles designed with 2-g buff strength have shown that the dynamic load causing incipient crush is often above the static load. Testing and simulation of a 2-g designed vehicle shows a crush load of nearly 4-g in this example [8]. Structural behavior can be unpredictable and in some cases the crush load after initial collapse drops in magnitude, potentially leading to rapid structural collapse of the operator compartment or the passenger compartment.…”

“…Given a static strength (buff strength) specification of 2-g for example does nothing to specify the car-body crush characteristic once the 2-g force is exceeded which can be expected in a dynamic collision even at speeds as low as 12 mph [8]. Dynamic simulation and testing of vehicles designed with 2-g buff strength have shown that the dynamic load causing incipient crush is often above the static load.…”

Explore the collision safety of tram and passenger vehicle under disparate right of way

“…Due to the large difference in shape between trams and passenger vehicles, some scholars have considered introducing the concept of collision compatibility into the study of collision safety between urban rail vehicles and passenger vehicles. Steven W. Kirkpatrick et al found that the mismatch of tram quality, shape and strength will bring risks to trams and passengers by studying the collision accidents of different types of trams [8] . Robert T. Bocchieri, combined with the research results of Steven W. Kirkpatrick, studied the front-end protection energy absorption device of the tram and found that adjusting the contour of the energy absorption device can effectively improve the safety of tram operation [9] .…”