I drove an expedited box truck, border to border and sea to shimmering sea from 2012 to 2017. (forced to retire when BP was too high" to pass DOT physical Yes. I was regulated, and under the same DOT rules as them piloting the 18 wheelers.)
All the companies the truck was contracted with (owner changed it 3 times) and the truck owner, had a simple driver's knife policy:
"As long as it can't be confused with a "weapon", we don't care what it is."
I carried a Old Timer 7OT or Buck 110 on my belt, and a large stockman, or sunfish and a "Demo Knife" in my pocket.
There were (still are?) some locations where I had to leave the 7OT/110 in the truck, because the then current usually local regulations demanded a blade no more than 3 inches. Also, some shippers and receiver's don't allow sharp/pointy objects on/at the dock. They could see if I had one on my belt, but had zero clue about the ones in my pocket. I left the 7OT/110 in the truck at those locations, too.
"Hidden" in the box, I had a Cold Steel "Heavy Machete" to break down abandoned pallets.
Obviously, you want to follow whatever the knife policy of the company and owner you're driving for.
I'd recommend keeping the blade length at or under 3 inches. Unfortunately, I was dispatched to Metro NYC area quite a bit, including, Jamaica, New York. (AKA: "JFK INTERNATIONAL AIRPORT")
Blades over 3 inches were banned at the time.
California was also knife (and everything else) restrictive.
For self defense, unless you have significant training and constant practice, forget a knife for that use.
It is still illegal in most jurisdictions to carry a knife with the intent of using it as a "weapon" be it offensive or defensive.
If a LEO asks "Why do you have that knife?" and you tell him or her "for self defense." you "win" a trip to the local and/or county jail house, and an added "bonus" of your truck and whatever you are hauling, being towed to the impound lot, and the headaches fines, and hassle of getting them back.
Seriously: If you're concerned about being attacked and self defense:
Number ONE: DON'T stop at the TA, Pilot, or any other truckstop at the East end of Dallas, for any reason... even though they have pay to park.
Their armed security guards have threatened, shot at, and robbed drivers at that TA. and Pilot.
The TA 18 miles closer to Louisiana is safe to stop at, and reset your clock, if necessary. Last time I was there, they didn't charge for 'parking, either.
Number TWO: (I'm not joking) Get a CCW from whatever state your drivers license was issued.
Most if not all states have a CCW now, (even Kansas!) and have reciprocal agreements with the other states to honor their CCW in both directions. The other state won't arrest or ticket you, so long as you are following the regulations of the issuing state.
If your resident state is one of the ten Constitutional Carry states (no CCW required. I remember Texas, New Hampshire, and Idaho are among their number), you can get a CCW good in other states under the reciprocal agreements.
It isn't illegal to have a firearm in your truck. Check with the company who's DOT number you are running under. It might be against company policy. (companies I drove under, including Panther, didn't care so long as you had a valid CCW to show any LEO and weigh station DOT officer.)
Good luck out there. Invest in a dash cam, if the truck don't have one or two, so you can prove you were brake checked, and it was the car that made a lane change into you, and not the other way around. (never hurts to have one looking back on both sides of the truck)
Thankfully, Paper logs are history, although you need a paper log pad in the truck in the event the electronic logs (Qual-Com, or other) go down. (very rare)
