A 35 pound 5 month old careering around at 30 mph can be very dangerous. I have been knocked over a couple of times, thankfully no damage to him or me. He seems not to make any effort to avoid me or my wife, who has become scared of going out when he is near bye. Any ideas how to stop this ?
Depending on the breed, some breeds mature slower than others. In either case, this is something that puppies do as they haven't quite learned how to coordinate themselves well.
Many times when training recall, calling a puppy to me, the puppy will be coming with such a speed that he will have trouble stopping when he gets to me and thus crashes into me.
So I would try the same method that I use for teaching recall in those situations: Basicaly, make sure you have an immovable object behind you (like a wall) and call the puppy to you.
You will have to get out of the way the first couple of times, but he will quickly learn to judge distance and avoid crashing into you.
I would not worry about the puppy getting hurt, as they start braking quickly when they realize that there's nobody there to break their crash.
Hope this helps.