I would probably be more likely than most to leave my vehicle but I have training in mountaineering and I wouldn't do so without a good plan and sufficient equipment. My car always holds a basic level of backup supplies including: a first aid kit, a bottle of water (which can also serve as a water container), a head-lamp with extra batteries, a multi-tool, matches, a fleece blanket, rain gear (including rain pants), mylar thermal blankets, and a simple drawstring backpack (which holds the blanket and rain gear) in blaze orange.
Even in a worst case scenario where I happened to drive up into the mountains in just jeans and a t-shirt and get caught in a snow storm and nobody knew where I had gone I could easily travel for several days through the back country (let alone alone the roads) with just that equipment. And if I stayed with my car it would definitely extend the amount of time I could survive until rescue arrived. The total cost of all of this stuff is almost nothing, it's worth it to be prepared.
I don't really leave a 2hr radius of SF now (although I guess I drive to Front Sight and Vegas sometimes, but prepare separately for that), and have all that stuff and more. Case or two of water, some tools, often a range bag with items, etc. Mostly worried about responding to someone else's accident, but there's the lingering fear of an earthquake, big fire, or other event like that. This is one of many reasons I like having my own car vs. zipcar or public transit -- it's 100 pounds of things to deal with emergencies (including "server broke, need tools and some network cabling", which is a much more common emergency for me than gunshot wounds...)
I really want to get into bay area amateur radio and get on some repeaters and stuff. An HT in the car seems like it would be a good addition. Maybe 2013.
Even in a worst case scenario where I happened to drive up into the mountains in just jeans and a t-shirt and get caught in a snow storm and nobody knew where I had gone I could easily travel for several days through the back country (let alone alone the roads) with just that equipment. And if I stayed with my car it would definitely extend the amount of time I could survive until rescue arrived. The total cost of all of this stuff is almost nothing, it's worth it to be prepared.