The American Trucking Association says that they prefer that DOT would focus on collision avoidance technology rather than things like improved underride guards:  https://annaleahmary.com/2014/12/the-passion-of-this-safety-advocate/

I now have a new response to that tiresome attitude toward vital truck safety measures–thanks to this Truckinginfo.com article:  http://www.truckinginfo.com/article/story/2015/10/behind-ups-decision-to-make-collision-mitigation-standard.aspx

“The National Transportation Safety Board recently recommended that all passenger and commercial vehicles use collision avoidance technology. The suppliers of the technology prefer the term ‘collision mitigation,’ because it’s impossible to avoid all accidents, but it can lessen the severity.”

In other words, because we know that we cannot prevent all crashes, it is unimaginable to me that we would not do everything that we could to make those crashes survivable!  https://annaleahmary.com/2015/10/rear-ending-a-truck-should-be-a-survivable-crash-why-isnt-it/