Border security

As a broker and consultant, I am very familiar with the vagaries of crossing the U.S.-Canadian border at several posts.  For the most part, the guards on both sides are compentent and alert, however, I wonder how secure even this border between two of the friendliest nations of the world can be.   I recently read a document from U.S. customs directed at exporters from Canada to the U.S.  Everything contained in the text was unexceptionally thoughtful and intended to help the exporter tighten the security around his packing shed and associated buildings.  However, once the truck leaves the compound, it is totally independent until the driver makes delivery on the American side.  Literally thousands of tractor trailers cross the border each way every day.  Just saying.