Is it really ok to make a Berner pull a cart and, if so, what kind of cart and how do you train them?

I am asking because my 13 yo can't take the long walks anymore, but it breaks her heart when we leave her. Maybe I could get Duncan to pull her along?

Well I do know that we looked into joining a club for carting with Bernese and we could go along and they would give you a trial go with your dog to see if it would take to it, if it did they were advising that you could only join seriously once hip scoring had been done. So I would make sure his hips are ok if you are thinking of doing it.