[dredmorbius]

Yes, underride or "Mansfield bars" (after actress Jane Mansfield who was killed in a similar accident).

Those are only rated for impacts to 35 mph. From the position of the Tesla in the image, it may have been travelling substantially faster.

The Tesla is also a deceptively massive automobile for its size, with much of that mass being low, in particular below the position of an underride bar, which might otherwise engage with the engine of a conventional vehicle. Effectively, the Tesla has a longer lever arm to apply force to the undderride bar. Whether or not that is a factor in Tesla-trailer collisons isn't clear, but might be something that warrants investigation and testing.