I don't know... I like my highway and the funny things that happen on it. I like knowing it happened because i built it that way, I made it possible.
I built a highway of smoothed stone from the edge of my map to the trade depot. It is just over 4 wagons wide. Shortly after its completion caravans and immigration primarily use the road to reach the fortress. Migrants seem to prefer walking on it. Wagons travel faster and in a straight line from edge to trade depot.
Now, you all know how nicely the caravan guards help out if a siege occurs or a thief is discovered.
As a caravan is leaving a kobold thief is found out, typical warning announcement "Thief! Protect the Hoard!" and the camera centers on the thief and the person it is adjacent to who made the discovery.
The man who found the kobold was the wagon driver of the lead wagon. With everything stopped and with no knowledge of just how tightly the game is made, I figured the wagon was stopped and the caravan guard has to take care of it. As soon as I unpause the wagon slams into the kobold at top speed, knocking the kobold back a few spaces before running him over. The wagon did not even slow down. The kobold left behind some blood and a chunk, and was only knocked unconscious. Then the second wagon runs right over him. Sending more pieces away and killing him. Then the third wagon spreads the carnage. Then the 4th wagon spreads the carnage. Then the mounted riders and caravan guard make a brisk march over him like he isn't there. Then the liaison jogs over him, catching up with the caravan after his trek out of the fortress. Then all the previously idle haulers from trade goods hauling duty swarm over the area like ants, picking up the pieces and all of the kobold inventory for storage. The highway has pretty gnarly blood smears over it for a couple days, until it rains and washes the blood away for a nice clean highway again.
...I did that. It is because of me that happened. I made a kobold into roadkill on the highway, and scraped him up and took his stuff. That is my Fortress! That is Ontak Deler, The Arm of Steel!