These are a nightmare at the moment in Cardiff, everyone beware. I've just had a £70 fine for the back of my van being on the end of the box at the Kitchener Road/Leckwith Road junction - heading toward the stadium.
I was aware of the traffic build up but a pedestrian decided to cross causing the car in front to stop prematurely, then a motor bike skipped around me (he can be seen doing it on the two still photos) and squeezed in front meaning I was trapped when the lights changed. Easy money, but I may try to appeal it.