Water Moccasin. Or Cottonmouth? I think:
I am travelling a low-traffic highway in Louisiana in 1990.
Ahead of me I see a large snake crossing the pavement. This was the biggest snake I had ever seen. Roughly 6 feet long and 4 inches around or so.
It disappears into the woods just as I come to a stop. I'm gonna check this out! I get to the edge of woods. Trying to peer in I realize that the bush is just too thick to find anything in there. I left begrudgingly.
I stopped at the next town to buy some chain lube for my bike. I mentioned the cool snake to the locals at the bike shop:
Apparently the Big Black Snake I saw was a water moccasin. Apparently it was a big one. Apparently they are territorial and will chase you down and kill you. Apparently I am an idiot and had a near-death experience and didn't know it. Thank God for impenetrable bush. Lol.
I will continue to pick up every garter snake I find. But I have been way, way more careful when being outa my 'hood regarding local wildlife.