No, wagons do run things over - I've had them discover and take care of kobold thieves in the same instant.
Was it perhaps the attendant guards that "did for" the kobold?
Which is not to say it might not have beent he wagon, but they do seem to occupy the same space as other things quite easily.
Case in point, last night I had an interesting time, with several things that surprised me. The Dwarf trading contingent came along, with four wagons and associated accompanying peoples. Now, I have the main entrance to my compound on its north side, but the wagons come from the south, so they started up the cutting up the centre of my map, just to the west of my area, which I'd specially dug so that they didn't try to encircle the eastern-central segment 'deep cut' area where I'm megaprojecting at the moment, and take too long to get to me.
To continue in the general theme of this thread... An ambush suddenly occurs (to the SE, too far from the wagons to matter, but bothering an animal trainer who'd gone out in the field to tame one of the chimpanzees who'd been caught in my cage traps), I set to activated the bridge/barrier at the compound entrance without thinking, and one of the wagons that had nearly reached it ended up with its horses 'on' the gate. The other three eventually started to turn around (blocky-wise) and I ended up with three wagons on top of each other in the cutting. And assorted merchant-types, all taking the long route around the deep-cut. Continuing even when I lowered the bridge. (As of making the Save last night, they were still wandering round the edge, untroubled by the various battles recounted and still to come.
Anyway, after dealing with the ambush (I placed High and Restricted traffic zones so that the Animal Trainer ran away from the goblins straight across a number of traps I'd put along that narrow border of the map between deep-cut and edge, they followed him and got swallowed up one by one
), and dealing with another attacking force from the western hills of my map[1] (shooting down upon my compound from the rise across from the cutting) by setting up another High Traffic zone along the leeward side of the western compound wall so my military could get to a good battle-position without being hit by potshots, and the fortuitous use of some more traps I have set up in the vicinity), I started looking at the trading possibilities.
I now have an awful number of caged POWs (encaged Hostiles and Invaders of various kinds) who I hadn't yet properly dealt with (I'm still perfecting my Death Pit), and I decided to send some up for trading. Of course, I did it wrong, and suddenly the Elf Guard (one of the Goblin Hoardes, and highly skilled in all three aspects of physicality) is disturbing one of my workers, deep in the depths of my fort where I'd (B)uilt his cage the previous year. Worrying that all my military are out and about, and wondering who inside I can conscript to dea with him, suddenly there's a red Splat! and he is no more. He'd hit a 10 (no-modifier) crossbow Weapon Trap that I'd set up early on in the fortress's life (to use up the first few low-quality crossbows made by the budding bowyer, and some of the bone bolts) and instantly died.
Then I notice that my Mayor/omni-Noble guy is wandering back across the deepcut (on a "Give water" task for one of the injured military guys) followed by a white "g". Not a gazelle (different colour) so I check, and it's a "Goblin..." ARGH! "...hamlet liaison". Ah, yes. He's a friendly. Forgot about him. Elsewhere in this forum I mentioned him and attributed him to the Human traders, but I'd misremembered the season, and he comes with the Dwarfs.
And the wagons were still trundling round, when I last saved.
[1] Not entirely sure if they're associated with the other lot. I have two neighbouring goblin civilisations, and the ones from the west seem to come along with archers whereas the ones from the SE never do. They often appear in quick succession, but other than that I can see no similarity or coordination.