Most effective answer to still allow box trucks would be a laser-triggered traffic light. They have these in a couple of places, Lincoln Tunnel in NYC springs to mind. Set it at, say, 9' high. Any vehicle over 9' tall sets off the traffic light, and the big fuck-off flashing red lights on a sign that says road unsuitable for tractor trailers, tight turns and rocks, $5,000 fine, turn around here, call xxx-xxx-xxxx if you need assistance. Box trucks can then proceed.