This is an interesting and worthwhile question I think, better than the usual MacGuyver scenario anyway. Let's start with handwarmers, those 99 cent doohickeys you might keep in your pocket for a cold day - a definite comfort for 24 hours on a stalled train, and it would make you look like Prince Valiant to hand them out to your neighbors. A couple hand warmers kept near your core can keep you comfortable for a considerable period of time - which is good for you, but a godsend to the mother of three who otherwise is stressed and worried about her cold, shivering kids. Then consider something that alot of us keep in our BOBs - heat cells (www.heatcell.com) are inexpensive and an easy way to generate a lot of heat, particularly in an enclosed place such as a stalled car, or here maybe in a stalled train. Now if I was travelling anywhere except to/from the airport, I might have one of these in my daypack, and a lighter to ignite it, for hours of safe and relative comfort. But given that I'm coming from a TSA zone aka airport, I lack matches or a lighter, and most likely the heat cell too - although if I was shunted onto the train from my car, I take my BOB from the trunk while I make my way home, and I have a heat cell with me then. I'm convinced a functioning heat cell would make yours the most popular circle on any train. Those will burn for about 12 hours.

With or without sources of warmth, this scenario is a good one to work on your social networking skills, talking to and taking care of people around you - you never know when a bit of social cohesion might be required should the situation become more dire. And alot of folks can be away from their meds (diabetes, anti-psychotic etc) - rally help for them. You want people around you talking and listening and contributing to solving problems like food to eat, warmth, and a bit of safety to get a few winks sleep etc.