What is a turn light? Is that like a turn signal or is it like a stoplight. Or us it their bastard love child?
A stop light turn arrow for vehicles turning left across oncoming traffic.
There are two reasons for these. One, to allow turning vehicles the opportunity to turn when oncoming traffic volume would be otherwise prohibitive, and two, to allow vehicles to turn safely where visibility for oncoming traffic is poor (bend in the road, coming over a hill, etc.).
Some regions have a flashing red arrow, meaning turn when safe, after coming to a stop. Sensible for intersections that use an arrow for scenario one described above. There is no reason whatsoever to maintain a solid red arrow when your direction has the green light, with full visibility of oncoming traffic, or the absence thereof. At least five turn arrows in my daily commute do this. Not another car in sight, half a mile of oncoming roadway visible, but I'm not allowed to make the turn. It's absolutely maddening.
I treat them as stop signs now far more often than not. Everyone should. Make them obsolete. It's not like they'll ticket everyone.
"Never half-ass two things. Whole-ass one thing." -- Ron Swanson