Autos and trucks are electromagnetic "boxes". Most cars/trucks are electronically controlled. The new "smart cars" have wireless built into the car, and anytime you are travelling with your cellphone on, you are also picking up cell phone radiation as well.
EMF Protection Solution for your vehicle: Hang a Room Shield anywhere in your car where it's convenient for you. Most people hang it from their rear-view mirrors, very close to the mirror so it doesn't provide a visual distraction.