I'd venture that you are going to get many opinions on this; here's mine--
To me, it's impossible to give a simple answer to your question, just because there are so many variables to consider-age and fitness of horse, weight of passengers, weight and balance of cart, suitability and proper fit of harness, terrain and ground surface the horse will be asked to pull over, speed you desire to go...are some of those variables! I believe there is general agreement that many miniature horses ARE, pound for pound, able to pull more weight than bigger horses; however, I also see lots of evidence that many people are prone to overestimate how much a miniature should fairly be asked to pull-and I caution against that. Your best guide should be good old COMMON SENSE.
All that said-a stout 36" or so horse, in good health and fit, should be perfectly able to pull two average-weight adults in a "Frontier" brand or comparable EE pipe cart (which weighs around 80-85 lbs. and can be properly balanced), with a proper and well-fitting harness, for a pleasurable 30 min. to an hour, perhaps, drive on reasonably level, reasonably smooth and firm, ground, combining periods of a pleasure trot and a walk.
Some will think this an overly-complicated answer-but the fact is, to be fair to your horse, ALL of these factors should be considered.
ENJOY driving your miniature!
Margo
