It might just be an artifact of the cheap-n-cheaty way in which I made it through this level, but it seems there is an invisible tank-sized object behind the actual tank, which is somehow connected to those two traffic cones up near the light pole. If I run into it, I’ll be pushed back slightly and one of the cones will make a large cloud of collision dust like a stuck prop. Eventually (by the time I took the screenshot) the cone wiggled itself free, and the area behind the tank suddenly became passable.
