Like most things in life, the yellow cap on a guard rail gets unnoticed. It's not particularly fancy, but it does do something completely awesome. That's right, I said the yellow cap-thingy is awesome. Hard to believe, I know. Basically, what it does is stops you from becoming a kabob when your car hits the end of the rail. So instead of the rail going right through your car, the yellow cap goes with your car and starts to peal off the rail, potentially saving your life.