The red & white reflective tape is a federal DOT mandate on trailers over a certain weight...think it is 10,000 pounds it becomes mandatory to be on the trailer sides, back as it is reflective.
School buses are also covered in reflective yellow tape down the sides, around emergency escape windows, around the back door and outlining the bus rear section and special stuff on bumpers...not sure we can use what is on school buses as they are under special federal mandates for some things no other vehicle is permitted to have..
All reflective tape can come in rolls, but realize that if you use the long strips and for some reason it lifts or gets pulled loose, you just unmarked a larger area where you are now vulnerable till replaced/fixed.
If you want just the strips of about 12" long and place them along the bottom of the trailer sides and rear go to a truck shop accessory store or truck stop and they have the good stuff.
I would suggest you place it on your rear doors and over the dual axles fender area so you mark the trailer in the dark...it reflects back easily to following drivers.
When you are pulling across a dark road at night, most trailers have only front side markers are reflective often and rear top clearance light, center of the trailer is dark.
..reflective tape makes you seen and alerts a driver of the dark hulking shape is indeed something to not
The reflective signs that say "HORSES ONBOARD" "CAUTION HORSES" for trailer rear...not a bad idea to make you seen...just make sure they are placed at legal heights as there are laws for such things many not know about...it has to do with federal regulations.
Make sure the size of reflective you pick will fit your trailer application as what works on a commercial tractor-trailer is not going to fit as well on your narrower 2-horse trailer 6' wide that may have rear doors that open, not a 8' wall of solid to affix that to...sizing can make a difference.