When I hit the road, whether I am towing my trailer or road tripping in my truck and staying in hotels, there are certain things that I must take with me. Some are for safety purposes, some in the event of an emergency and some for comfort. Here's my "Must Have Road Trip Essentials" list.

Safety 

Tire pressure tester and tire inflator.  Always check tires when they are cold. 
Car Emergency Kit 
Car Tool Kit 

When buying a tire pressure tester and inflator, make sure that you buy one that runs on a battery. When you need to inflate the tires, you many be someplace where eclectic is not available.

Make sure your car emergency kit has:

Reflective Warning Triangle ,
Reflective Safety Vest,
Tow rope,
Gloves with Gripping Palm ( 1 pair) ,
Safety Hammer and Seatbelt Cutter,   (good for breaking windows if necessary)
Hand Driven LED Flash Light ,
Adhesive Tape,
Jumper Cables,
Whistle

Make sure that you buy a car tool kit and not a home repair tool kit. A home repair tool kit has items to help you hang pictures on the wall and change an outlet cover but won't have adjustable wrenches and socket sets that you will likely need in the event that you have to make a repair or adjustment under the hood.

 

Emergency Items 

WD40 – loosen things, keep things from squeaking,
Electrical tape – to cover LED lights and to actually use on electrical fixes
Duct tape – to keep anything together!!
Wire cutting splicing tool – in case you need to fix your 7 way plug
Phone charger – car battery may be dead
Portable jumping kit – many on the market, can also charge your phone
Spare tire – not just a spare but the tools and know how to get at it
Old school Rand McNally Map – I’ve been in places too remote for GPS and also just like to study the map and see where the backroads are leading me
Firs Aid Kit – VSSL
Snow Supplies (scraper, shovel, lock de-icer, blanket, good gloves)
Fix a Flat – at least two cans - keep them in the car and not in the trunk
Zip ties – endless uses – not good for license plates though
Back up Fluids – washer fluid and anti freeze
Lighter – may need to start a camp fire or, God forbid, a signal fire
Emergency flashers – More than just the triangle one that comes in Emergency kit. Several for highway.
Luci Light
Flashlight

I have used almost all of the things I carry "just in case." Over time, even if I don't use it myself, I have had the occasion to loan it to someone in need. Most of the things in my Emergency list don't take up very much room and are

Comfort Items 

Cauldryn hot water boiler 
Tea, coffee, instant soup,
Protein (nuts, dried fruit, peanut butter, crackers)
Car pillow
Two gallons of water
Blanket
Umbrella
Rain coat