I believe in the GHB (get home bag) concept of preparation for this scenario and many other mass destruction urban scenarios.

IMO:

1. 'Fallout' consists of fine radioactive dust particles, and it travels on the wind like any other dust that size. Travel upwind to avoid it

2. There will be no consensus on the bus. The most agressive/armed person will take it. Get out and walk back to your car

3. The bus doesn't matter anyway as the roads will quickly become impassible, again; get out and walk to your car and turn on the radio

4. Get to your GHB with it's water, heavy clothing, boots, poncho, tarp etc and walk home if home is upwind. If it is late afternoon, prepare to hide at night.

5. If home is downwind, consider staying with your parked car, moving it slightly for shade, security, etc, or walk to find safe shelter (large store, office building, etc) upwind depending on circumstances.

6. Don't depend on a police officer to stroll by and inquire as to your well-being. It's not going to happen anytime soon.

7. You will be responsible for your own security. Ally with someone, trading the shelter of your car for the security of two or more. There is a tradeoff here. Do not think that just because you own the car, they will submit to your direction. Choose your ally carefully.