The side effect I'm apparently experiencing doesn't involve drowsiness. People fall asleep while driving or talking on the phone without being sleepy. My neurologist says taking less carbidopa/ levodopa might make it better or might make it worse. I can't believe nobody has done a study about that.

There is a problem with getting sleepy for a period of time after taking your C/L. Maybe you are taking too much??? I'm not sure. Check with your doc. There is a chance you will get used to this dosage with less sleepiness after a while, I think. At least, that happened to me.

I keep a bottle of Starbucks espresso at hand & also eat energy snack mix one piece at a time. This helps me avoid the sudden dive into the steering wheel, borrow pit, or oncoming Mack truck.

I have no idea. However, they do have those headbands that keep you alert.

It sounds like you need to stop driving until you figure out how to stop the sleepiness. Even if you don't actually fall asleep, your reaction time will be slowed by your tiredness. That's dangerous to you and everyone else on the road.