The lone individual utilizing a primary 180 degree observation window which is supplemented by a intermittent 360 degrees( at eye level) is likely to be extremely limited in regards to detecting danger within an active public space which they do not control. Badguys have a substantial advantage which they will undoubtedly exploit. Still, it is prudent to put a realistic effort towards general awareness. Just don't let your solo efforts develop into a false sense of security. You may only have about a 30% handle of what is actually developing in your "situation".If you are watching and paying attention to what is going on around you when you are carrying, as you very well should be doing anyway, you should see anyone that comes around acting suspiciously or paying too much attention to you.