This is in California.

I saw a young man driving an older Jeep Wrangler (with the fold down front windshield). The windshield was folded down and he was operating the Jeep while wearing a motorcycle helmet. My guess is obviously to keep the wind and bugs out of his eye and there must have been something wrong with the windshield since it was folded down.

California law requires helmets for drivers and passengers of motorcycles and all-terrain vehicles, but mentions nothing about passenger vehicles.

Just curious if anyone knows if it is perfecty okay to drive a passenger vehicle with a motorcycle helmet on.