How do you judge that number to be a lot? Are you comparing it to something else you're already familiar with?
That's like finding 20 empty two liter bottles just lying there. (Based on a bottle using 50 grams of plastic.)
So yeah, seems like a lot to throw out every year from every car.
Put another way, if every driver threw an empty two liter bottle on the side of the road every two weeks, you'd have an equivalent amount of plastic being shed into the environment.