Courtesy or Money Saving?

I've seen trucks with what looks like fringe over their trailer wheels. What is that fringe called and what purpose does it serve?
Terry

-----
Response from Mike Simons:

Most commonly seen on UPS trucks, this fringe (I believe) is used to reduce the amount of spray that comes off the trailers' tires when roads are wet.

Additionally, this move to help nearby vehicles improve their visibility is a good one, because it can help reduce the number of accidents.

We wish all professional truck drivers safe travels and lots of money saving opportunities on the road.

Best regards,
Mike Simons

https://www.truck-drivers-money-saving-tips.com/