Can somebody ELI5 why trains are so loud in Phoenix? Forgive me, I've only lived in Phoenix a couple years but noticed that the trains blare their horns at all hours of the day/night. Is there a reason why there aren't any noise restrictions for freight trains and railways? Tempe has a "Quiet Zone" ordinance, so I'm wondering why there isn't one in Phoenix? 

I grew up in Toronto, literally lived next door to the commuter and freight rail lines, and the noise was never this bad.