Since this is set in America, this should have one of the most iconic things America has, and it is its long nosed Diesel semi trucks. These trucks would have a lot of use for players that wants to live the travelling nomad life, they would be safe in a large truck with a Sleeper behind.(A Sleeper is a the part of the truck where Truckers sleep, eat and entertain themselves). It would also give a lot of utility to communities if the time ever comes to Multiplayer where large groups of players have banded together with NPCs. These trucks could be their lifeline in supplies themselves or blockading a street. The challenge in having a truck in the Apocalypse would be:
Repairing it and up keeping it. Trucks have larger tires than normal cars, so after a while, finding replacement wheels would be extremely hard(Trucks usually have 22.5 tires).
Refueling a truck could take a lot of effort. For example, a 1980s Peterbilt 359 with a Sleeper and 6X4 Chassis would need at least 300 Gallons per Football Field to be fully refueled.
Maintenance would be a nightmare as trucks do not have usual parts that you could use on cars and you would need to find a Truck shop to get the proper parts for it.
Space, trucks need a ton of space to be stored, so unless you have a warehouse as a Safehouse, you would have to park it in the open, for everyone to see.
Lights, trucks have a TON of lights, from the roof of the cab to the sides of the Cab and Sleeper, some would even have Spotlights, old time trucks in the 1980s would have Spotlights and Long Reverse lights attached to the top of their chrome driver and passenger side windows.
These bad boys uses 4 car batteries, good luck with that.
Majority of trucks use 12 Speed or 18 Speed Eaton Fullers, so the player has a lot of shifts to do to get it up to speed. Some like logging trucks has High and Low gears for Hills and Mountain roads.
There are different types of trucks too, Day Cab, Flat top, Cabovers, Logging, Military and Sleepers.
Day Cab: A truck that only consists of the Cab, it is shorter and used for local trucking industries as it could fit in almost anywhere and has a smaller turn circle
Flat top: One of the most famous types of trucks in the 1980s and early 90's. These trucks has sleepers that has flat roofs.
Cabovers: A very old design of trucks used way back then in the 80s and 90s when road regulations on truck length wasn't harsh one many states.
Logging: These are the types that could plow through large hordes with ease, they are city trucks equipped for the harsh muddy roads of the Mountains. Large bullbars and headache racks. Mostly seen in Day cab with the headache rack behind the cab to protect the driver from the Logs his hauling.
Military: The military uses many types of Civilian trucks converted for military use like the M915A5. A Freightliner converted for Military transport.
Day Cab 1978 Peterbilt 359
Flat Top 1984 Peterbilt 359
Cabover 1994 Freightliner FLA
Kenworth T800 Logging truck, the thing you see behind the cab is what truckers call "Headache" rack.
United States Military M915A5 with a M1015 Flatbed Trailer (If this is too modern, there is always the M35 Semi used way back in the 70s)
The benefits would be great for anyone. A truck could travel a thousand kilometers in a single tank, large hordes would be nothing as you just plow through them with a trailer, and it would be good as an intimidation to players on the road or walking along it. But one should always remember that trucks have air brakes, so you cannot just be constantly be tapping the brakes since it would lock and would take a lot seconds of revving up the engine(It is to pump air into the brakes) to unlock. They would also be noisy, and more noisy with the trailer jumping on and on in tight turns or just from speed.
In terms of trailers, the usual 48ft Fontaine Flatbed and 53ft Wabash Dry Vans and 48ft Refrigerated Reefers you see everyday should be scattered on Industrial areas, these are their Pros and Cons:
They would have large utility, but are hard to use since if you do not have a Semi truck, they cannot be moved.
Replacing their tires would also be hard after a Month into the survival since they also use the same size as the Semi trucks.
Hooking up a trailer would also be a hard thing if you do not know which airline to attach and how to hitch the 5th wheel.
Though the creativity that could spark if you have a 48ft Flatbed, you could turn it into a house, towed battlewagon, and car/parts/object carrier while the Dry Van would serve the same purpose just excluding the battlewagon but instead as troop carrier or a more enclosed house or moving storage facility.
The Dry Van could be used as a temporary or permanent blockade since 53ft is a very long length and could block off Highways and entire entrances to towns.
The Reefers(Basically large fridges) could be used to freeze captured players to death or store large amount of foods. But it has a Generator and would need to be attached to a Truck to work properly.
These trailers has the ability to "slide" their axles to balance out the weight, but since this is the Apocalypse, they'd be just there as an option if you want to slide the Axles backward.
Wabash 53ft Dry Van trailer
Velocity Fontaine 48ft Flatbed. The one on top is a Dropdeck with Spread Axles
Here is a link to how Axles slide on Dry Vans:
Now for the more complex trailers like Bulk tankers and specialized trailers, these should only appear in specified areas like construction sites and Gas stations. There are multiple types of Bulk Trailers and you'd see. I'll just post a picture since it would be complex to explain it all. The examples I'll use are from a Tanker Company named Polar Tanks.
I don't know all the liquids they carry but the examples I could give is:
Petroleum: Used to store Diesel and other types of Gasses. Up to 80,000lbs.
Dry Bulk: Used for Cement and other types of Construction materials that are in liquid form.
Chemicals: Used to haul dangerous chemicals from factories and is often called as the most dangerous type of trailer as if one could leak, an entire town could die.
I cannot explain the others as my American Truck Simulator knowledge on tankers ends there, you guys might have to ask actual truckers on what they do.
Here are more types of trailers:
Wilson 42ft Grain Trailer, these should be found in large farms.
There is two types of Dump trailers, one that is called "Side" Dump trailer and "Full" Dump Trailer, here are examples:
EAST Full Frame Dump Trailer
JET Side Dump Trailer
And here is an example of a "Lowboy" trailer:
JET Tri Axle Lowboy trailer, these are used to haul Construction equipment or just heavy vehicles in general.
Thanks for looking into my suggestions! Keep doing great Devs!