This didn't happen to occur near the 2818 overpass did it? If so, I see that quite a bit from northbound traffic making a U at the light (prior to going under the overpass) to head south on 2154 (Wellborn). It can take one by surprise if the car suddenly stops at the green light, no turn indicator and then turns. We call it "the Koppe Bridge maneuver due to witnessing many drivers pull out of the parking lot, cut over to the left lane and then turn. I rather wish it were illegal there because it seems to catch a lot of people offguard.
Edit to add: I have also seen this occur on Southwest Parkway back when the overpass was first built and the onramp for 2818 was moved from the west side over to the east side. Folks would drive through the light and then realize the access they were seeking had vanished. Often they would head up to SP and then make a U turn and head south again.