I don't do paved roads (I have a serious phobia regarding asphalt and horses!), but I do hack quite a bit on the miles of gravel roads around me. Depending on the time of year and how much time I have, I do it at least once a week (this time of year, when the fields and woods might be too mucky for much hacking, I may do it every time I ride out of the ring). With my horse (prelim-ish level, small TB that gets fit very easily), I am averaging about 45min to an hour right now. We mostly just walk, though I do in-cooperate some trotting, some rides more than others(I only trot on the flat and up hill. I know people who just trot up or down, but I just feel that that puts FAR too much pounding on his feet). As he gets fitter and we get closer to competition season (and during competition season) we'll go for more like 90 minutes (our usual route is 7 miles out and back). Like I said, mostly walking, as I think the long, slow mileage over the hard surface is what is the very best thing for the soft tissue that I am trying to make strong and resilient.
This time of year, I really don't worry too much about the frozen ground and the roads. He's not jumping and galloping on hard going like he could potentially be doing in the summer months, and he's not out stomping at flies on the hard ground like he would in the summer months. Out in his pasture, he moves around, mostly at the walk with occasional bouts of hooliganism. I rather he be on the frozen than the mud (our other state of being!).
I am trying to add in shorter cool down walks along our drive, too. It is 15-20 minutes from ring to back to gate to barn (basically traversing the drive twice).
If you are looking to add it in, start slow. Just 20 or so minutes to start, gradually adding in a few minutes every week or two. I would also suggest sticking to the walk until you can march on the road for 45 minutes to an hour. Then just add the trot in a little at a time, as well. I never canter (unless he bolts...which happens ).
I love using the road and I'm always kinda surprised more people don't use it if they have it available. It can be a little too exciting sometimes (traffic, dogs, cows), but the benefits outweigh the risks. *Knock wood* I think the long, slow hours on the road this past year is why my horse's legs have been so cold and tight all year. My farrier whines about the wear I put on his shoes, but he can shove it! I much rather have strong, cold legs and feet than shiny shoes.
I don't really put conscious thought into paved vs not. I ride on some roads because if I want to condition for endurance rides, that's about all I've got. I won't canter on pavement, but I will walk and trot on it. My guy is barefoot for what its worth.
We do 10-15mi a night, 2-3 nights a week, that includes gravel (which I will trot and canter on), pavement, grass and farm fields (during parts of the year). I don't really say I will trot for X amount of time on the pavement. Its more a we're trotting here regardless of what happens to be underfoot. My Arab is trained to break gait to a trot or walk if we are cantering and come to pavement.
We use the paved road across from us almost all winter. Though we do not ride (we drive our ponies) and we do mostly walk, with a bit of trot mixed in. I find it really gets them used to things as we go through sub divisions. This way they see people mowing lawns, dogs barking, kids running around etc and they have all taken it in stride. Through the summer they are shod all around with corks and in the winter they are bare foot. Its a nice and easy pull for the ponies and they do seem to enjoy getting out, especially since its really hard to drive anywhere in the winter! We only go out for about 30 mins in the winter (as it gets really cold when you are not riding!!) and we incorporate it into our summer work outs. We do a bit of ring work, then field work, then cool out across the street. It has worked really well for us for the past several of years and we have even won conditioning awards after we have done our marathons. We have even completed our section A, D and E (about 12km total, 5ish km of trot, 1km of walk and the 6km of the hazard part of our marathon) and we came to our final vet check, they told us we were good to go to start our section E of the marathon!! They were so suprized when I told them "We have to go again!??". They couldnt believe we were finished....
Barefoot and endurance ride training would make a huge difference. My horse is shod all around and, unlike the foxhunters in the area who will gallop down roads, is not studded. So, I am careful regarding pavement (I have fallen on pavement and I am the first to admit that I am overly terrified of it!). The barefoot horses I've ridden on pavement were far more solid on it than the shod horses.
Also, like hunting, in endurance, you go where you need to go at whatever pace you are going at. We don't need to do that in eventing (yes, footing may change, but not from grass to pavement....and every time I've been at events that cross roads, the organizers go to great length to cover the pavement or gravel with dirt and/or bluestone).
My point being, I am conscious as to how I use my road work because it isn't typical for what he goes on to compete or train. I use it to make him stronger for his job, but it isn't PART of his job, if you understand my meaning.
I do road work ... it's normal in the UK. My ponies are barefoot. Over there, as a kid, we were pretty much stuck on roads the majority of the time, and everything was shod. (This was 30+ years ago). There was a significant amount of sliding and falling. It's MUCH better barefoot. We use it as part of a conditioning program that aims to gradually build up solid bones, ligaments, muscles.
I will work on dirt roads, packed screenings or frozen ground at walk or trot for long periods riding out. It very much helps strengthen soft tissue . I don't do asphalt, simply because all of ours has a lot of traffic on it. I think it's an excellent and important component of conditioning -- I also work in mud, sand, and anything else I can find so when I get to competition, LOL, bring it!
I ride on the roads a lot. I do occasionally even canter on pavement, although you should be careful about slipping - driveway sealant is like ice with horse shoes, but regular road asphalt is not. I don't know that it's any harder than a hard-packed dirt road, and it will have fewer irregularities (divots and rocks).
Start slowly - lots of walking is great for the soft tissues, and build up to trotting. Depending on the horse, trotting can be more concussive than cantering. While I don't set out to canter a mile on pavement, I don't panic if we have a few strides on it.
I am more careful about up/downhill and unevenness than I am about which surface I'm on, as long as the horse is fit. I do try to find different footings so when I get to something different, whether at an event or just out riding, the horse is accustomed to it. If all you do is work on a harder surface, deep going is potentally damaging.
My guys walk out on the road at least twice a week - approximately an hour + of walking each time (as we get closer to the season, the Prelim horse may add a third hour each week and/or combine a walk with flatwork; the BN/N horse will hack only on hack days). If the weather's bad and/or the outdoor ring is frozen, they will hack more often. We also have access to primarily gravel roads, though I've walked out on asphalt before and been fine with it. I actually don't trot or canter on the roads unless absolutely necessary, since I have access to big fields and great footing, I figure it's not worth the concussion. This time of year, they both get quarter sheets or coolers while walking out and I bundle up like an arctic explorer.
Rules for our guys are that they have to walk, not jig, and while they don't usually walk on contact, they have to walk straight and with purpose - no flinging themselves around. We try to set the groundrules early in their lives for that, as it makes hacking out so much more pleasant even when they are fit.
Most of the winters on average around here, SE PA, aren’t too bad. But when we get snow or our gallops get “greasy” from a freeze-thaw we road work our fox hunters and steeplechase horses. Keep in mind these horses are already pretty fit. Our standard “around the block” is a bit over 3-5 miles which we trot then about a mile cool down. All of the horses have steel shoes with borium “tacks” spread around the shoe. Gives them excellent traction on cold hard blacktop. Some farriers are stingy on the amount and number of “tacks” and not very good at “welding” them on. Our guy isn’t and doesn’t charge much extra compared to some we have had in the past. We are blessed with access to quite country roads with mixed flat and hilly areas. We will do a bit of short controlled cantering up some hills. As others have said it good for their minds. Exposing the young ones to lots of different sites. Trash days makes for an interesting outing on the young ones. The big blue monsters take a little getting used to.
Just one thing to add--knee boots! Many years ago I had a horse fall on rough pavement--the knee he landed on was pretty seriously shredded (but fully recovered thanks to a vet with amazing needlepoint skills). Since then I put knee boots on if I know we'll be riding on pavement for any length of time. Won't trot on pavement without them. Shires Westropp are my favorites, as they are quick on/off once adjusted for a particular horse (each of mine has his own pair).
I walk my guy on the pavement. I'm like Yellowbritches, it makes me nervous, but I have to do some pavement to get to our gravel roads. He's shod in front with studs in winter, barefoot behind. I only trot on the gravel, he's a bit older so I'm protective of his back and joints. I put him long and deep and make him walk with his back up, up and down hills, which is doing awesome things for his fitness and his dressage as well as hardening the soft tissues. My favorite trot workouts are in the spring when the gravel roads are a bit soft--we'll trot for 10-20 minutes at a stretch then.
We hack out once the weather cooperates (has been consistent -20s celsius since early November...) along the gravel and field roads, and when crops are off or fields aren't seeded, we hit the fields. The closest paved road to the barn is about 8 miles.
We do mostly walking, try to get out 2-3 times a week once the spring thaw comes, throw in a few long steady trot sets.
I don't do fast work on the pavement but I will walk out on it with tiny bits of trot, my horse is barefoot and has pretty good traction. Right now all my work is pretty much 'road work'. There's no indoor at my barn so with the cold and no snow, (boo!) the ground is pretty much concrete. I can, however, go pretty much any weather and footing. I have hoof boots with ice studs in them so if it's really icy, I can put them on and walk out with a purpose.