Audio Systems: AM Car Radio, rf interference, radio waves

Question
QUESTION: I have the same problem in my Toyota 4 Runner and Prius.  The FM radio works fine.  The AM radio has significant interference, I believe RF interference, when I am in the proximity of high voltage transmission lines, bridges or overpasses with steel in the concrete structure, etc.

Could this be caused by a condenser failure?  Or is it some other problem?  When I am out in the country with no steel ro metal around the radio works fine.  

Paul

ANSWER: do you have window tinting in both vehicles ?

---------- FOLLOW-UP ----------

QUESTION: Only the slight tinting recommended with AC.  

What does this have to do with my radio?

Answer
toyota is using the antenna in the back window  next to the defroster lines
if you have window tinting with metal film ,it will stop the radio waves

we have remove window tinting from at least 100 cars for the same radio reception problems
good luck