PHOENIX – It can be easy for students to miss a quiet oncoming light-rail if they are skating, texting or wearing ear buds, but it was hard to miss the sign-toting, wings-wearing “angels” next to the tracks. That’s the point of Valley Metro’s guardian angel campaign, which aims to get college students to be more aware of their surroundings around the light rail. Besides playfully delivering a serious message, Valley Metro officials hope the guardian angel program spreads across social media to help prevent accidents.