Not to be any sort of jerk, but until you've spent enough time cycling in traffic to be comfortable, your intuition regarding the safety of that activity is suspect. Several factors are involved. First of all, there is the risk compensation phenomenon (http://www.ncbi.nlm.nih.gov/pubmed/21418079), which is also seen for seatbelt-wearers etc. and causes users of any "safety" device to behave less safely to compensate for that use. This phenomenon also applies to other road users, so that when they see a cyclist they perceive to be "protected" by a helmet they don't give her as much space, they drive faster, etc. (http://www.sciencedirect.com/science/article/pii/S0001457506...) Other factors are follow-on effects from the fact that requiring helmets reduces cycling rates (http://www.nber.org/papers/w15658): fewer cyclists make for more dangerous roads for everyone (http://www.ctc.org.uk/campaign/safety-in-numbers) and cyclists who cycle less aren't as good at cycling. There is a "rhythm" to riding in traffic, and after I've taken some time off, I have to be more careful until I sharpen up. With regular practice, you know:
- exactly how close the damn delivery truck is going to pass, just by the engine
sound
- which car is going to change lanes without signalling, not from its brakelights
but from its slight pause in acceleration
- how fast you have to pedal to intimidate an entering SUV into waiting for you
to pass instead of turning left completely across all lanes
- the distinct whine of a BMW (the official car of assholes) that's going
to attempt a right hook from 50 feet behind
- etc.