Upon a brief and, apparently, unfruitful examination of the sign in my previous post, a co-worker of mine remarked that the sign "obviously" means that no explosives should be transported on the road. "Not to take away from the humor".

That is in no way the "obvious" meaning of the sign. I put forth that any such sign would look similarly to this (although it may be rendered in some more high-tech application than MS Paint):



As you can see above, there is a stick of dynamite painted on the side of the truck, and the red crap indicates "NO". Hence, "no transporting of explosives" is indeed the obvious meaning.

The Chinese sign features a car where the roof is actually exploding. This is a key part of the sign's meaning. Since trucks carrying explosives are rarely in the process of, themselves, exploding, it would seem odd that the sign would focus on such an unlikely scenario. So it must be that the sign is against cars that are exploding at the time that the sign is observed.

One may also find it interesting that, although the car is pictured to have an explosion eminating from it, the car itself is unscathed. If a car was indeed carrying explosives that exploded, it would appear as follows:



I hope I have only deepened the mystery, all humor aside.