Wow, that is really lucky there was no accident. I hope the horse will be fine. That much galloping on pavement can't be good for feet / legs.
My sister's 1/2 Tb mare made the news like that, years ago. She was out in a pasture, another horse chased her and she went right through the fence and kept going straight and ended up downtown.
She hit a cyclist on the way, a mentally challenged young guy who went home and said he was ran over by a horse - of course no one believed him, until they watched the local news that night!
The mare was caught by the fire department and when we got her back, she had some abrasions and cuts from wiping out on the road, but she healed fine, and never was lame. She was never turned out with that bully horse again, lol.