i always travel with people that are slower than me.  In the event of an unwarrent attack like a crack head knife wealler, I throw my slower freind in the knife attacker's path and run like hell. 

I like that. You could throw some thing and tell him it was crack. Then run !

hi im new here but i might have an idea. I just started taking tae kwon do classes and the most effective thing to do if someone stabs at you is to do a Knife-hand block, grab the upper part of their wrist firmly, turn the wrist counter-clockwise which will cause them to turn, and as they turn grab the back of their neck with your other hand and keep holding their hand so that the knife is either facing their throat or abdomen. i practiced with my sister holding a pen lol.