A British woman driving home from a shopping trip captured dashcam footage of someone driving a mobility scooter on a 40 mph highway.
Miller said the scooter appeared to be going far below the speed limit.
She sent the video to police.
"It didn't have a license plate," Miller told the BBC.
"It just looked so dangerous. It's a bit of road where you've got a lot of cars coming on, and going off, across five lanes."
"It's bad enough when you're in a car -- it's a horrendous bit of road," she said.
The Highway Code allows motorized scooters that reach at least 8 mph to drive on roads, but only with a flashing amber light signifying the slow-moving vehicle's presence.