If you can't walk 13 miles in one day...
then you deserve to die. How this group isn't able to wake up when the sun comes up and walk 13 miles to the checkpoint is beyond me. Yes the one guy is injured and can't walk at all, then leave another person there with him for company and safe keeping and START WALKING. Even if you go in intervals of walking 2 miles and jogging 1 mile, you're going to get to the checkpoint before night falls.
Personally I didn't like this movie. I didn't care for the characters at all, and when they died I didn't feel any remorse for it either. If anything I was rooting for them getting killed just so it would end and I could leave.