It's a common experience. You're in one lane and things are going fine. Suddenly, you realise that the lane you're in has become a turning lane for turning left and you have every intention of heading straight on.
Your pulse increases a bit as you shoulder check for traffic in the other lane. You have to merge quicksmart, as you are approaching the stationary traffic waiting for the turning signal and nobody likes being rear-ended, especially with your big box.
Ahh, there you go. A quick and fluent movement and you slide into the right lane, behind the other person who just passed you.