It has got to be a special person whom you would willingly trap yourself in a car with for hours at a time. Road trips can make for a special kind of hell on wheels.
The dream: Someone who shares your taste in music, can handle the car you're in as well as the traffic around you, and can navigate without exhausting their data plan when you're driving.
The nightmare: Someone who sings all the notes wrong, gets triggered by every other car on the road, and snores from the passenger seat when they aren't correcting your driving technique. Also, body odor that could stun an elephant.
Of course, since we're pulling candidates from television, we're also looking at individuals of certain skills, temperament, and luck. Many of them come armed.
Tripper - Red Reddington - The Blacklist
Red would probably have a driver to do all the driving and upgrade the car to boot. Only drawback would be the very real danger of ending up in a shoot-out or having the car blow up.
Tripper - Lt. Cdr. Bortus - The Orville
Bortus would be the most reliable road buddy to have co-piloting even if he probably wouldn't have much to say. Also, since he can eat literally ANYTHING, he's never going to complain about your choice of pit-stop restaurant
Rager - Sydney Barrett - Legion
Although she's super smart and would totally have your back in a pinch, extended up-close and personal time with Syd Barrett means an increased chance you'll accidentally make physical contact with her and end up switching bodies which, by all accounts, is disorienting and probably a good way to get into an accident.
Tripper - Mazikeen - Lucifer
With her insane (!) survival skills and an innate ability to intimidate the H*LL out of anyone giving her trouble, Maze would ensure that you feel safe (from threats other than her, of course) on your cross-country jaunt. You may have a few problems crossing a border if she forgets to leave her weaponry at home.
Tripper - Pops Johnston - black-ish
Pops would know ALL the places to go, people to see, and scams to be run. He may gamble the gas money away at the track but he'd probably also know how to siphon some off the SUV parked beside you. Man's got SKILLZ after all.
Rager - Adam Strange - Krypton
Yeah. No. Adam Strange may WANT to be a super-hero but the dude's all sorts of unreliable. He's always got an angle and his sticky fingers are bound to get you in trouble along the way. Furthermore, since he (supposedly) has limited control over that darned Zeta-Beam, he's bound to disappear to Rann or Krypton just when it's his turn to drive or pay.