Move to Yorkshire, no hedges, it's all dry stone walls.
I beg to differ. I can assure you that the Vales of York and Pickering are full of hedges, most of them hawthorn, whose thorns are just the right length to remain intact but be detached from the hedge by a flail mower and prop themselves point-end upwards in the road.
Some flail mowers are equipped with a big fan which effectively blows most of the cuttings off the tarmac and into the verge, so no sweeping is required (although on windy days, the clippings may simply blow back into the road).
Other flail mowers are not so equipped. It's vanishingly rare for a farmer to actually sweep anything up with a broom or another machine; so much easier to simply allow motor traffic to do it for you.