HOUSTON—For most U.S. drivers it has been a consistent threat to their safety for almost 40 years without them ever even knowing it.

And the problem has gotten worse in the last 15 years with the growing popularity of SUVs and other light-weight trucks.

In fact, safety advocates have told the Department of Transportation and the industry time and time again about this alleged danger as other foreign automakers fixed the alleged defect long ago.

So what is it? Why has it been allowed to stay in place for so long? And what do automakers have to say about it?

Watch Jeremy Rogalski’s investigative report tonight at 10 p.m. It may save your life.