East of Indianapolis, I-70 has been under much (and needed) construction the last several years. Most all of it has finally been completed, but the reduced speed limit signs remain. That's 55 mph and if you exceed it there are dire warnings about consequences. So what is a motorist to do? Drive that speed and get run over or go your regular speed?
Going a regular speed over 55 mph could cause an encounter with a police man and you have to worry about a Barney Fife who would be a stickler for the law. "I know there is no construction, but you have to do what the sign says."
As I drove through Indianapolis, I was seeking local stations to see what they had. Today is evidently the agreed upon testing of the emergency broadcast system with that grating noise. Sadly, not all the stations do it at once. I must have heard the test five different times.