About 10 years ago, freight cars began to appear with these 4"x18" reflective strips. Its an effort to make cars more visible to improve grade -crossing safety. I've tried in the past to use striping from auto parts shops to replicate this effect and never got the results I wanted, until now.
I found Smokebox Graphics of Reese, MI sells a complete line of these strips, already cut and sized for O gauge cars. Best thing is there is almost no wrong way to locate these on a car. The main requirement on the real car they must be at least 42" above the rail and 12' maximum spacing. [ 7/8" and 3" in O gauge].
Smokebox also makes yellow and white striping for sides on modern day diesel loco's some roads use a solid stripe the length of the loco, others [bnsf- wle- some csx ] use the 4x18" stripes with spacing .
All my loco's and about 1/2 of my 500 freight cars have these highly light- reflecting stripes applied. Here are a couple of before and after photos to help show the difference in car appearance.