What I didn't see in advance was the guy who slipped through traffic, ducking and dodging around cars that sped past him too fast to notice him until they'd already missed him.
He slipped right up and picked up the paper cup.
I honked in surprise and then pulled over to call the police. He slipped through traffic and got to the call box before I did.
"Please don't call traffic? I'm just trying to pick up litter," he said plaintively.
"You're going to get yourself killed!" I objected.
"No, I'm fine!" he said, flashing me a little ID card, "I'm a ninja. Well, a reformed ninja. I got busted and so I'm doing ninja highway cleanup for community service hours."
"They let you do community service hours for ninja-style assassinations?" I marveled.
"No, of course not. I had an expired registration tag, repeat offender."
Remember, ninjas: keep your car registration up to date!