Thanks for all the advice and commiseration everyone. I've finally been able to put into words why I feel more vulnerable on the bike than I do on foot. On a bike, your hands aren't free (since you have to hold onto the handlebars), you can't change direction quickly like you can on foot and you can be knocked over easily. The advice of "abandon the bike and take off on foot" feels like Russian roulette. If you do that, the attacker can then either take your bike, destroy it or hop on and chase you down with it.
After lots of thinking yesterday I opted for a few safety measures:
- a personal alarm. It's in a little pouch on the strap of my messenger bag so it sits in the center of my chest and is easily accessible. It makes an insanely loud sound of a woman screaming.
- a kuboton on my keychain. However this will be of no use on the bike, since I don't carry my keys and when riding my hands are already occupied because I have to hold onto the handlebars.
- A frame pump that pressure fits into the frame, just below the top tube. It will do double duty as a backup to my CO2 pump and a baton
- a helmet cam as soon as I can either find the one that @Ottawa suggested locally or get it online.
- I'll also be taking some self defense classes
I opted against pepper spray. I'm pretty sure I'd get it in my own eyes and lungs. I already have asthma and the idea of my lungs closing up seems like a bigger risk. I also have two young children and I really, really don't want them to accidentally spray themselves. They won't be able to hurt themselves with any of the items I've chosen.
Good for you TrMama on taking some active steps to be prepared! I hope you're already feeling better by having some defenses ready.
As far as being on your bike, you have both advantages and disadvantages there. It's a reasonably fast method to flee and outpace someone on foot, and when you're moving you're not a particularly easy target. But you're correct that you're vulnerable to being knocked over on it if someone surprises you. Your best defenses are to:
1. Avoid dangerous areas in the first place (less populated areas where attackers could be looking for victims, and where you are away from help if needed -- places like jogging/biking trails without a lot of traffic, emptier streets/sidewalks/alleys, far reaches of parking lots or garages, campuses, etc.).
2. Be aware of who is around you, and keep a safe distance away from anyone who is potentially threatening.
3. As mentioned by others, maintain eye contact with others near you -- just give them a brief look that says, "I see you there."
4. If you can't keep away from someone threatening you, then dismount and be ready to run to safety or fight. Don't think twice about your bike, give it up and seek safety or fight. Worry only about protecting you. Don't worry about someone taking it and chasing you down, then they'll have the same disadvantage of not being able to get you with their hands, or you knocking them off it.