photobug56 wrote: ↑Fri Oct 08, 2021 10:21 pmUS commuter trains tend to be fairly slow so higher center of gravity might not be as much of an issue.
Metra and NICTD South Shore run bi-levels at 79 MPH and their design may be more "top heavy" than the superliners (placement of heavy air conditioner units in the center of the car above the entrance foyer). Without checking I'd say the cars weigh less (empty) but "top heavy" refers to where the weight is placed, not the total weight.
Focusing on the topic of this thread: Did using superliners cause the incident? I do not believe the use of superliners was the cause. Did using superliners cause the crash to be worse? To be determined officially, but I would lean toward "yes" not because the "top heavy" accusations but because of the NTSB noted window size issues.
It is harder to keep people protected inside the aluminum can train when the walls are made of glass and hitting the ballast shatters the glass and turns the glass and ballast into damaging if not deadly projectiles. Compared to aircraft design both single level and superliner cars have huge windows. One of the selling points for traveling by rail is the view. But the windows offer less protection than a heavy frame.