Hello Jeff, I understand what you are going through. You have all the training in place, you have painted the items in a yellow color, you have gone over the safety issues in the warehouse and you have physically taken them through the warehouse and shown them where the hazards are, but you still have drivers running into these obstacles. This is very frustrating not only from a training aspect from from the management side of the house also, and yes the drivers actually get frustrated also. I have never worked in a union shop, but what we do when we have incidents like this is go over refresher, just as you stated you do, but if it continues we first give them a three day layoff with NO PAY....this usually wakes up the people that truly want to keep their jobs and makes them focus more on the task at hand and if that does not work, well termination is next. Another thing that you might try is ask the drivers what they think can be changed to prevent this from happening, get their input and let them be a part of the soultion. One small thing you might want to try, and you might already have done this, but paint a large yellow area around each column and crane and instruct them this is a NO DRIVE area. Who knows, the simplest things might help. Hope you find a solution, keep us informed