Aren't postcards fun? I can only assume the driver was feeding them something, but what a concept for a town's promotion!
You do see that sight these days though the car will probably be more modern. :) It's supposed to be an offence to feed the ponies. The same for New Forest ponies, they roam free. There is a strict speed limit in the New Forest to avoid accidents and I'm sure that's the same on Dartmoor. In reality, the ponies tend to keep well away from the roads but you can never be sure.
Thanks Sheila, it's nice to know that the scene still happens, I know if I'd seen this postcard as a child I would've wanted to go on holiday there :)