A two+ hour drive would really take it out of me. I would often have to stop and have a 10 minute nap.
I’ve found meds have really helped, I still feel tired, but I don’t have to sleep afterwards or take naps.
Same with riding motorbike, but double. I think it’s the intense concentration for long periods of time.
Even with meds. Not so much anymore, but when I was commuting to college. And not just when driving. I would get really drowsy seemingly randomly sometimes to the point of having little split-second visual hallucinations (extremely rare though).
Come to think of it, I was also taking Zyrtec (OTC allergy medicine) at the time, and I think drowsiness was one of the side effects. That might’ve been my issue.
Could be drowsiness inducing for you for sure, but in general generation 2 antihistamines are incredibly non drowsy. Only mention it because it is so fascinating. It took us like 30 years after finding Benadryl to find something that won’t put us to sleep.