I have done more than my fair share of galloping on roads, as a member of the field, as a whipper-in, and these days on the annual Pony Express reenactment. As you might imagine, much of the original Pony Express trail is paved these days, including interstate highway and metropolitan Salt Lake City. This means, for each two-mile relay, pavement the whole way- and no I won’t flat out gallop, especially when one has traffic lights to obey, but a nice steady canter does the trick, I won’t go faster than a trot on the steeps in the canyons, though. But I can tell you I HAVE gone flat out on Route 15, south of Gilbert’s Corner, passing a VW beetle and playing chicken with an oncoming semi, to get to a spot to ensure that hounds wouldn’t be harmed on the road.
Shoes and borium are essential. The wear on a barefoot horse’s feet would be unacceptable to me. I can tell you that I have yet (knock wood) to have ANY ill effects on any horses from speed on hard surfaces. The one that had the highest hard surface mileage was also one that hunted pretty hard from ages 6 to 26.
Two things are, I think, essential. First is as J Swan noted, conditioning. You should, in the course of getting any horse fit for hunting or other strenuous activity, do a fair amount of walking and trotting on hard surfaces, good conditioning for those tendons and ligaments. Second- though I was originally, as a kid, taught to never gallop on roads, I’ve since learned that the risk for injury isn’t so much the consistency of the footing (rock hard to knee deep in mud) as the SUDDEN CHANGE in footing. IOW you are as likely to risk injury to the horse going at speed into deep plough as you are from soft surface to hard. The key, therefore, is where a significant change in the footing is encountered- trot the first little bit of that to allow the horse to adjust.
As gothedistance notes, whether it’s paved roads or a number of other hunting possibilities, the idea is not to risk life and limb, slow up for a bit. Caveat though- if you find yourself constantly having to fall back and then catch up, that might be a sign that you’ll want to drop back to a slower flight. You are supposed to be enjoying the day, not fighting constantly with issues outside of your comfort zone.