What if as you are sitting there you blow a hose or get a flat?
Your thoughts?
I'm not that kind of guy, M.
Seriously, very good question. I'll mention a couple of related considerations that have occurred to me, and what I've done about them.
For starters, I've realized that our family cars are natural and great places for survival equipment, because our cars are ALMOST ALWAYS WITHIN A COUPLE HUNDRED YARDS OF WHERE MY FAMILY MEMBERS ARE. For years, I kept my survival gear in a closet at home. Not too useful when I'm at work miles away from home--or in law school 2,000 miles away from home. Now, I keep layered and redundant survival gear all over.
Experience has taught me three unique problems about cars.
1. They are easily seen-into, and broken-into, even if locked.
2. They need to be affirmatively locked each time one exits, or the contents are there for a thief's taking.
3. They are subject to SPECTACULAR variation in temperature, which needs to be taken into account in stocking survival gear in cars.
Here is what I do in response to each of these problems.
Problem 1: Visibility.
Anything I leave in a car within sight, I try to make look as unattractive as possible. I approach this from what I imagine would be a thief's mindset. That means that I even remove bags that I know to be diaper bags, containing nothing of stealable value, from the car, to avoid having someone smash my window. Even if they only get half a dozen Pampers and a box of baby-wipes, I've still got to vacuum broken glass out of the car's rug. Also, I think what would be thief-tempting will vary somewhat from place to place. A box of food might be relatively safe in front of my house in the suburbs, but it might be a real temptation out in a remote trailhead.
For cars with large amounts of concealed space--like a trunk--visibility is less of an issue. For cars where there is not a lot of concealed space, I deliberately scatter survival gear throughout the space that IS there--under seats, in the glove compartment, etc. I try to keep the thief-interesting stuff under the seats, but an old pair of boots, etc. might go somewhere more visible. Not only does this let me keep the more-valuable stuff out of sight, but it also makes it harder for a thief to grab my entire survival kit in a 60-second smash-and-grab. Downside: if I have to abandon the vehicle, I will also have to pick around and collect stuff. Good idea to keep a list of what you have and where it is, maybe on an unusually-colored piece of paper, in the glove compartment. That way, when your wife has your car and needs the tire inflator and you're not around, she can pull out your inventory list (keep it current, guys!) and go right to where it is. (This is also relevant in that your survival stuff will, as a practical matter, get used twenty times for non-emergency purposes for every one time it's used for emergency stuff. The Leatherman will get used to cut apples far more often than to skin that deer you hope to bag with your homemade bow after the SHTF, etc.) Another good idea is to keep some kind of carryable bag somewhere, so you can have something to put your scattered gear into for a little trek. (If you have, say, a cheap daypack for this purpose, you can keep it under the spare tire, or under a seat, and just load it up and expand it to non-concealable size if and when the need truly arises.)
Problem 2: Break-in-ability of cars, and problem if car is left unlocked
If someone wants into your car, he can usually get there. Cars themselves are desirable objects of theft, and even if your bugout bag doesn't draw a crook, your car itself might. Wives and kids have a way of leaving doors unlocked.



Thus, anything you keep in the car is potentially more subject to theft than what you keep in your bombproof vault at home. Answer: I tend to keep my more-replaceable, second-string survival gear in the car. A car is also a good place for stuff that is a little heavier than what you'd carry on your person.
Problem 3: Vast temperature variation
I live in the Sonoran Desert. Every summer, guaranteed, the temperature will rise to 114 degrees, and usually more, on at least one day. That is the AIR temperature. Measured in the SHADE. At an altitude about 6 FEET OFF THE GROUND. In my town, that temperature has been recorded as high as 122 degrees Fahrenheit--or 50 degrees Centigrade. Temperatures inside a closed car, where the glass traps in the heat, can get MUCH HOTTER THAN THAT. I think a low-oven temperature of 150 degrees is not at all unrealistic.
In the winter, it will predictably freeze. Every year.
This means that whatever I keep in my car is going to have to hold up to those extremes (unless I'm going to count on regular rotation of stuff--something I don't like to build in a need for, since that's the kind of thing one easily tends to forget. If I'm planning for things like this, I try very carefully to avoid setting things up to require predictable fixes, to the extent possible.) Things like wax candles, I just don't bother with. Food that can dry out, I count on doing so. (Even plastic pouches of jerky have their contents become rock-hard in a year or so of storage in my trunk.) Liquids may expand--so I'm really careful with what kind of stove fuel, etc., I keep. Anything leather needs to be saturated with leather-treatment material of some kind, or it will literally crack and begin crumbling into dust in a period of months. That means spare boots, knife sheaths, leather knife handles, etc. Sometimes I've opted for dive knives and the like for car survival kits, as anything waterproof is unlikely to dry out in the heat.
On a related note, I try to avoid leaving clear canteens full of water where the sun can shine through and be focused on a small area, causing a fire. (Cody Lundin is to be thanked for this warning). Consider covering any clear canteens with a belt-pouch; that'll also let you carry them more easily, if you need to leave your car. Also, everything in a car will vibrate. Keep this in mind if your car kit contains strike-anywhere matches. Also, the car's mobility means that it will end up in places other than where you usually keep it. Good idea to weigh the idea of storing your legal-in-your-state gun in a car that your wife will be driving on a visit to her relatives in an adjacent state where that gun is illegal. If your kit will contain anything that will be illegal to take anywhere, make sure you are very aware of which items need to be removed for which trips, and keep those items where they can easily be removed. For instance, I often go to court. ANY knife is illegal to carry there, so I leave all knives OUT of my wallet survival kit, which goes with me wherever I do, and which would probably get me stopped at the court security checkpoints whenever I forgot about it, if I carried a knife in my wallet. Instead, I keep my knives in kits I won't be carrying when I go to court; anything I am carrying, I will just remove before heading off for the courthouse.
Returning to Mercop's scenario, I have deliberately rethought my planned bugout routes to exclude some otherwise-attractive routes that would leave me in a potential traffic jam with no way out--I've favored routes that go through country with lots of driveable terrain to either side of the road, and which veer away from the obvious out-of-town freeways. As for anyone looking into our stopped car for stuff to take, most of the survival gear is, as stated above, stored out of sight as a matter of course. Any additional stuff can be covered with blankets, newspapers, and/or (I love this) trash. A carful of kids can very plausibly generate a huge pile of hamburger wrappers, paper cups, napkins, etc., and it doesn't take much of this on top of a newspaper to make it look like your car is just brim-full of junk, even if you've got a week's supply of food and a generator underneath it.
Those are just my thoughts. Thanks, Mercop, for suggesting the ideas.
Anyone else?