Overpasses become clogged with cars when hail starts as it is, so what happens when 50 cars stop to jump in the shelter? Who's going to close the door last?
The public needs to be educated on what to do in severe weather... but that generally goes out the window when panic sets in. People don't leave their mobile homes/cars to seek substantial shelter as it is, especially in places where tornadoes don't occur on a regular basis i.e Tuscaloosa/Springfield, MA. Unless the event is predicted and warnings are issued with enough lead time people will likely die in any large scale event. As far as highway safety, Texas has built Safety Rest Areas with large parking areas and reinforced buildings. Problem is these stops are few & far between and mostly rural.
In the recent OK event on May 24, the early warnings made a difference. State offices were closed early and many people left for home or a shelter by mid-afternoon. Of course OKC and more populated areas were spared but the public was informed days in advance of the potential of severe weather and being prone to it the public listened. There were 10 fatalities and atleast 3 occurred on I-40 near Calumet. The count would have surely been greater without the lead time.The real issue is the disconnect between the public and traditional media. Many radio/tv stations no longer interrupt programming with weather info. Then again many people no longer tune-in. Social media can be used to pass the message but more & more I just think we've about reached the mark on getting the message out there... it's simply common sense and reaction time and not everyone is going to heed the warning much less hear it.