Every woman you know who goes out alone...
Every woman you know has held her keys in her hand
Every woman you know has locked the car as soon as she gets in it
Every woman you know watches out for males when walking alone
Every woman you know has done a detour to check if she is being followed
Every woman you know has done the "safe home" phone call
I could go on...
As women, we automatically are aware of our surroundings when alone, we look for threats. We have done it all our lives. And I am sorry to say there is another level to this now in an "integrated" society.
I saw some men commenting that they too are sometimes scared alone at night. Yes, you are scared of other men, not a single woman walking down the street.