Not only will these things be useful to you if you are stuck in a less than ideal situation, these items will allow you to aid another motorist if they are in distress with their vehicle.
1. First Aid Kit
Generally inexpensive, a good first aid kit should be kept handy in your vehicle just in case of an emergency. Included in this kit should be the materials needed to patch up a wound, cover a burn, or create a sling in the event that it is needed. Having a first aid kit on a road trip can be a lifesaver, and preparedness is the key to surviving an emergency. Many motorists never get one, and this is a huge mistake.
2. Fire Extinguisher
Ideally, your fire extinguisher would be rated for Class B and Class C fires by the NFPA. This would ensure that the extinguisher could eliminate fires involving both flammable liquids and electrical equipment—both of which are present when encountering a fire within a vehicle.
3. Reflective Warning Triangles
Many times, these triangles come in prepackaged emergency kits, but it is advised to have at least 3 in your vehicle. You should position them approximately 50 feet apart to warn oncoming traffic when you have become immobilized for any number of reasons.
4. Foam Tire Sealant
This is an inexpensive way to repair a flat tire without having to replace the whole tire. Its most useful when you get a flat tire while in some remote location. It may save you from an emergency trip to an auto shop till you are able to take the time to find the best place to have it repaired further if needed.
5. Tow Strap
This would be useful to you or another stranded motorist. The strap should have enough strength to tow 6,000 pounds.
6. A Gallon of Water
Because water can serve so many purposes, it is one of the main essentials to have in your car at all times. Water can take the place of a coolant in a pinch, it can be used in the windshield wiper tank, and it can be consumed if you become stranded in a barren place. More than one gallon would be great, as the minimum should be a single gallon.
7. Tire Gauge
Not just for the tires that are being used, but motorists should be periodically checking the air pressure in their spare to ensure that it is properly inflated. It would be awful to realize that you have a flat tire, but your spare is flat as well.
8. Multipurpose Tool
A multipurpose tool will be able to act as a screwdriver, scissors, files, and many other things. A few companies that makes these are Leatherman and Swiss Army Knives.
9. Jumper Cables
These are a necessity just in case your battery dies, or they can be used if you encounter someone in need. The jumper cables should be at minimum 10 feet long and should be coated with no less than 8 gauge rubber.
10. Flashlight and Extra Batteries
A waterproof flashlight would be ideal, and you should keep a few extra sets of batteries to go with it as well.
11. Nonperishable Snacks
These are snacks like dried fruits, nuts, granola, crackers, meat sticks (like Slim Jims), and cookies. Not only will these save money, so that you will not have to stop every so often for food, but they will be handy just in case you have an emergency that renders the vehicle immobile.