Whats with the bridge in map "breaker"?

I just noticed at the end of the lazer beam theres a bridge that randomly raises and lowers so you can drive over it or perch on it it folds like a collapsible chair. when its up you cant drive around the lazer you have to jump the p’it. any ideas? cant find out what determines it going up and down. not sure if its score in ctf that triggers it or if it just goes up when the lazers out. thanks.