Doh! Doh! and Doh!

I have to keep repeating this plea until everything comes clear to me.

RE: IRAQ:

Cars and trucks, including ambulances, can be outfitted with deadly explosives.

Cars and trucks, so outfitted, can be driven into Iraqi areas with civilians, politicians, the military forces, and police.

Such outfitted cars and trucks can be detonated, thereby killing and maiming many personnel within the scope of the explosive.

It happens over and over and over and over and over and over and over and over, again.

CONVERSELY.

When cars and trucks cannot enter areas with all of the previously cited personnel, their explosions cannot harm those personnel.

PLEASE HELP ME TO UNDERSTAND WHY CARS AND TRUCKS ARE ALLOWED INTO THESE URBAN TARGET AREAS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

I guess I am just too stupid to get it.