Do you mean that two Rotem cars, or say a Rotem and a covered hopper, should have been crashed?
Or just a Rotem and hiway vehicle of some sort?
And surely there has been more than one Rotem v Auto on Metrolink by now ???
There have been a bunch of crash tests over the years.

The idea was to establish design criteria instead of 'proof tests' to destruction.
That said, I did look up the tests that were done a few years before Chatsworth.
Apparently the reasoning behind those tests was that a 60 mph++ crash was
so improbable that such test would be of little value, albeit expensive.
As aside, on this day of remembrance, IIRC the designers of the WTC towers DID consider an airplane collision- a 707 of that era. In WW2 a B25 hit the Empire State Bldg
It will be interesting to see the report[s] and compare the design [ or actual construction]
with typical locomotive pilots.
Perhaps a wrassle with the FRA/DOT website will turn up reports of interest