Tackle him and go directly for the weapon hand as soon as possible. Bruce Lee once said that the person with a knife is at the disadvantage because he has really only one point of attack, while the person unarmed has many(fists, knees, elbows etc). Obviously the guys one form of attack is deadly but he will be focusing on trying to stab you and not hit you with his off hand for example. So you trying to neutralize the attacking hand should be your top priority.
The thing is in the street everyone waits for someone else to take care of the problem, and only when the others see someone doing something will they jump in to help. The second someone gets control of the situation even for a couple of seconds others will join in and swarm. Trying to restrain him is best IMO because if you succeed for a few seconds others will help join, however if you attack him then it becomes a one on one if your attack didnt daze him enough, and others will most likely not join.
Last edited by Soakked; 08-31-2010 at 02:27 PM.