Driving the kids to school yesterday, we were in the middle lane of a three-lane road (in our direction), behind what looked like one of those rented moving vans, except it lacked any markings whatsoever. Anyway, that was the approximate size and shape of this vehicle. Traffic was a little heavy, as the right lane was blocked due to some road work (morning rush hour being the ideal time to tear up a piece of road, naturally). Up ahead was an intersection with a double left turn. Since traffic in the left lane splits up into people going straight and two lanes of people turning left, the left lane has a tendency to empty a little more quickly. And, since the right lane was blocked off and people needed to merge, the middle and right lanes were moving much more slowly.
I'm usually one who just stays in his lane, because if I try to switch to a faster lane, invariably I end up reliving the opening scene to Office Space, where as soon as I switch lanes, I come to a complete stop as the lane I just left speeds up. And on the rare occasions when I do seem to gain ground, I notice that a car I passed up manages to catch up to me two lights later anyway. So why stress, right?
In this case, this truck in front of me decided he wanted to merge left. Possibly because that lane was moving faster, possibly just to make room for the people in the right lane to merge. Either way, he waited until the left lane traffic lightened a bit. As soon as there was an opening, he'd turn on his signal.
The instant that signal came on, the people in that left lane would hit the accelerator and close the gap, making sure they got across that two or three car lengths of empty space before that truck dared to get in front of them, and then slam on their brakes to narrowly avoid hitting the stopped car in front — but at least they prevented the unthinkable, someone merging into their lane.
I watched this happen two or three times. Different people each time, because it would actually put them in front of that truck, so the next time it was someone else coming from behind to claim the empty space as theirs.
And what did they gain? Despite being two or three cars ahead, traffic as a whole was still moving rather slowly. Whether you are behind a big truck or not, you're still not moving more than 5mph at best, and it's still three light cycles before you get through the intersection.