The concept of the bag is fairly simple and the items in it are relatively inexpensive.
It can usually be assembled with a lot of items that most drivers already possess, but more importantly can really make a difference in times of need.
-Small backpack/old book bag
-Brightly colored plastic rain poncho
-Walking boots in the winter, tennis shoes for summer — better for long walks than dress shoes or high heels
-Thick wool socks
-Four bottles of water
-Four granola bars
-Small homemade first aid kit in a zip-top plastic bag
-Basic map of the city you live and work in
-LED flashlight with spare batteries — for night time travel and vehicle repair
-Cell phone charger, vehicle and regular outlet capable if possible
-A written list of emergency numbers and addresses — remember cell systems may go down for a period of time and there may not be access to that information off of a phone
-Wool cap, gloves, scarf
-A few chemical hand/foot warmers
-Blanket or sleeping bag
-Ice scraper for a windshield.
A two-gallon gas can — an empty gas can will be hard to buy when hundreds of people are trying to get gas at the same time. Consider that one gallon of gas may not be enough considering heavy traffic, but that a five-gallon can will weigh 40 pounds when full.
This list can be expanded to include more items, but this may be enough to get out of a tight spot. A credit card, cash and a prepaid calling card should be able to pay for a ride, buy more food and water and to call loved ones for help.
Pay particular attention to specific medical needs and pack enough for a few days — such as insulin kits and seizure medications.
Do not forget fuel will be important so when there is a potential for the weather to get very cold or icy, gas up all the way before the event strikes.
In the wintertime refuel to have a full tank when the half-full mark is hit in the gas tank.