A huge part of the on-train segments of The Final Station is keeping your passengers alive. Doing so is quite easy, but the game does not explain how you do it at any point.
Whilst exploring the zombie infested outposts, you will find survivors that want a ride on your train. When you return to your method of transport, they will be waiting for you and as you move to the next area you, need to keep them alive and the train moving.
Each passenger has a hunger and health meter that can be replenished by food and medkits. The supplies you find around the world can be used on yourself or on passengers. You have to decide whether to keep everything for yourself of help the survivors.
To heal them, head to the front of the train and pick up food or medkits from the relevant place and take them to the correct passenger. As long as the health and hunger meter of the passengers don’t deplete completely, they will stay alive.
You probably won’t be able to save them all due to low supplies, but learning how to save them early will help in the long run of The Final Station.