When you ride a bike on Pittsburgh roads, you are acutely aware of what is going on around you. Unlike driving in a car, you can't take your environment for granted or allow you mind to wander too far from the task at had, that is, keeping from getting run over by some asshat talking on his cell phone.
It's not paranoia if they really are out to get you.
That having been said, you cannot afford to get tunnel vision. Focus only on the the road and the vehicular denizens that troll there and you can miss out on other things that are going on around you. Things that can be vitally important. For example, had I not looked up I would have missed this sign:

There was no panic in the streets as one might expect from a zombie outbreak, but in all honesty, with Pittsburgh being the Zombie Capital of the World™, zombie-ish cubicle drones, faux-zombies and zombie cosplay are common enough that an actual zombie might be able to go unrecognized for a considerable amount of time. Even so, I would not expect the authorities to allow people to freely come and go from the building involved if, as the sign said, there really were "Zombies Inside." The news did not have any recent reports of missing persons, mysterious illnesses, violent insanity or other characteristic symptoms of a zombie outbreak. There have been no black helicopters. No upsurge in the numbers of out-of-state or government vehicles. With this evidence (or rather, lack of evidence) it only took a few moments to conclude that I did not have to continue with implementation my Zombie Plan beyond step one or two.
It's comforting that these thoughts and conclusions flowed smoothly and without panic in the time it took me to ride half way around the building and take the above photograph. Vigilance, a broadening attention and an organized plan lead to natural and effective action. Not security theater as is practiced at airports and by those overly concerned by terrorism but actual intelligent safety.
It did remind me that there is a gun show in two weeks and I haven't been to the shooting range in too long. I should buy some ammo and get some practice in.