ASME RT-1-2015 pdf – Safety Standard for Structural Requirements for Light Rail Vehicles.
4.6 Crashworthiness
The carbody shall be constructed in such a way as to
(a) minimize the possibility of injury to occupants during a collision from such causes as parts detaching from the carbody or equipment falling from the ceiling or roof
(1) minimize the loss of occupant volume resulting from structural collapse or structural penetration
(c) provide for a progressive controlled collapse of energy absorption zones of the carbody structure while limiting the average longitudinal acceleration
Structural energy absorption zones typically located at the outer ends of the carbody structure shall be activated prior to crush of other carbody structures, following the sequence and magnitude of collapse as specified in Tables 3 and 4. Tables 1 and 2 further specify required strengths for structural elements such as collision posts and corner posts, to protect passengers and operators from structural penetration and loss of occupant volume in the event of a collision with another vehicle or obstruction. Other requirements in Tables 1 and 2 specify design criteria for vehicle anticlimbing protection in vehicle- to-vehicle collisions.
Collapse shall not commence until the end sill compression load identified in Item 2 of Tables 1 and 2 has been exceeded. The end sill compression is the minimum allowable value for the initiation of crushing, with the exception of the energy absorption in Zone 1. The design end sill compression load shall be selected based on the CEM and collision survivability plan per section 8.
The performance of the energy absorption zones shall be validated through the collision scenarios specified in Tables 3 and 4. An LRV carbody shall be designed with three sequential energy absorption zones, and a streetcar carbody designed with two. Vehicles shall have geometric compatibility to enable performance of the designed crush and energy absorption mechanisms. The structural energy absorption zones shall function in sequence (i.e., the initial impact energy shall be fully absorbed by Zone I prior to the absorption of impact energy by Zone 2).
— Zone 1. The first zone is designed to absorb impact energy in the event of a relatively low-severity frontal collision with another LRV or streetcar. This energy absorption zone can be designed with a replaceable or recoverable element.
— Zone 2. Having consumed the energy in Zone 1, this zone is intended to accommodate collisions between two single like LRVs or streetcars with a closing speed up to 24 km/h (15 mph). Crush shall be limited to the vehicle cab section, There shall be no loss of survivable volume in the passenger and operator compartments. Proper functioning of this zone requires that the anticlimbers in both LRVs or streetcars engage to prevent override or telescoping of the vehicles.
— Zone 3 (Applicable to Light Rail Vehicles Only). Having consumed the energy in Zones I and 2, this zone is intended for higher-speed collisions to absorb the additional energy associated with collisions between two single like LRVs at a closing speed up to 40 km/h (25 mph). The crush damage in this zone shall be limited to the front cab sections of both colliding vehicles. Inelastic deformations in the passenger compartment are allowable only if a survival volume is maintained.
After all the energy absorption capability in the three zones has been exhausted in a collision, the crush behavior of the vehicle shall continue to occur in a controlled manner progressing from the cab end in a rearward direction.
The operator’s cab door and seat shall be designed to allow quick emergency egress of the operator into the passenger compartment. Armrests on the operator’s seat shall fold back or be easily movable to permit easy egress, and the cab-to-passenger compartment door shall open outward from the cab.