So here's my set-up. Four characters need to get out of Dodge—essentially, they need to travel the equivalent of 35-40 minutes by car, along roads that are paved but unused for several generations and probably not in the greatest condition. They've got a horse, which is fairly healthy, and a mule, which is undernourished and old.
The characters themselves aren't carrying much, if anything, on them. I've got one very big guy, one slighter guy, a verging-on-skeletal young woman, and a scrawny teenage girl. Can I believably get all four of them riding out of there, how far can they realistically get without killing the animals, and who should be riding what?