cgmarine...
You think bad publicity is going to prevent Mexicans from coming south and bringing gifts to relatives? Better separate Mexicanos from extraneous. Bear in mind cars with FRONTERA Mexican license plates go through exactly the same procedure as extraneous. Tens of thousands of them line up at the Banjercito windows. Tens of thousands have to pass through ADUANA and argue with aduaneros about the value of their gifts.
It was absolutely just as bad in the early 1970's. Why? Usually one single ADUANERO to write car permits and inspect luggage. Two lane potholed roads. As far as delays are concerned it matters not if there is a single line or 8 parallel lines to yours each with 64 people waiting. Four lanes of clogged traffic is every bit as frazzling as two.