Martial arts is still the best preparation (after you get that bike in good working order). With martial arts, you never have to worry about whether you remembered to bring your weapon, or whether you can reach your weapon, or whether you can remember how to use your weapon... Because you are the weapon. A basic instinct animals follow is to avoid injury when they can; this applies to human animals as well. A human "victim" who appears weak or afraid will present an opportunity with a low probability of injuring the attacker; the attacker's strategy will be to scare you into giving up what they want-- in this case, your bike, most likely. If you have the confidence to stand and fight, and are ready and willing and to take the attacker down, they have to reevaluate the situation, because their number one imperative is still to avoid injury. That's why guns are so effective-- because the attacker doesn't want to be killed. With martial arts, you're still presenting them with the possibility of serious bodily harm. And just like with the gun, the key is your ability to harm them, and your willingness to follow through on that. That doesn't mean that some idiot will always back down-- that's why you need to be prepared to follow up on the threat you present-- but most people want easier pickings. Finally, with martial arts, all these other self-defense with weapons options are still available, only you can use them effectively. Imagine the difference between an untrained cyclist using a bicycle chain/padlock combination as a weapon, and martial artist who has practiced using the bicycle chain/padlock combination as a weapon. Put one martial artist on the street, armed with a chain he has practised with, and put him up against those two guys who chased you last night, and watch them **** bricks when the martial artist stands and fights.