A few further thoughts on the "Car as Shelter" theme. Most of this will be obvious to folks on this forum, but it is probably worth stating anyway. Looking at someone else's suggested list of what to carry in your vehicle is a starting point, but everyone needs to evaluate their own situation, and decide what is appropriate for them. Some things to consider:

What sort of kit are we planning?
Is this a general kit that will stay in your vehicle all the time? Or are you planning a kit for a particular trip such as a vacation? Or is it a getaway kit for a particular scenario like Florida in hurricane season?

What sort of environment will we be in?
Obviously Alaska or Canada in winter involves some different considerations than Tucson in the summer. What is the likely worst case? What is the worst case you can possibly immagine? Is it an area I'm familiar with, or someplace where I'm not sure what to expect?

What sort of roads are we likely to be on?
Interstate highways? Dirt roads in the mountains or desert? Populated areas with lots of potential help around? Or a long way between help with little traffic?

What are the most likely problems?
Are you concerned about a "carmegeddon" scenario on the DC Beltway? Or a breakdown out in the desert? Both could be a bad situation, but require different preps.

Aside from what's in the kit, how will I be dressed and what else will I be carrying?
If you are heading out on a hike you are probably dressed for the outdoors. If commuting between home and office, you may want to consider some weather appropriate outdoor clothing in your kit.

What sort of vehicle are you driving? How much extra space do you have?
If you are driving a Ford Expedition you have room to take most anything you want. If you drive a Smart car, you need to plan very carefully.

What is your level of skill and confidence? Your level of health and fitness?
No point in carrying stuff you don't know how to use, or are physically unable to use.

What is your tolerance for discomfort? Your tolerance for risk?
Are you comfortable with minimal preparations for only the most likely problems? Or do you feel the need to be ready for even the most highly unlikely scenarios?