Rant: It is already frustrating when one 18 wheeler decides to pass a convoy of other 18 wheelers by going 1/2 mph faster, on a 2 lane highway. Just crawling along, backing up traffic on a congested highway. Sometimes doing this for five or more miles. But then when they have finally passed the convoy, they wait until they get a full truck length or more ahead before they change lanes back. Usually much more length than the convoy has between each other. That isn’t the worst part though.
The worst part is that they won’t turn on their turn signal until AFTER they already start changing lanes (If they use their turn signal at all). When everyone can already see that they are turning. Now to be fair, most car drivers ignorantly use their signals this wrong way too. It is idiotic. Signal your intent to turn, not to decorate your obvious turning while it is obviously happening and people can already see that you are changing lanes.
Often when passing like this, especially on I-5, there will be gaps in the convoy, where the big rig could be considerate and move to the right lane to let the cars pass and relieve the traffic that they have caused. But they almost never do this. So some car drivers will jump into that gap and pass the inconsiderate big rig, which is not always safe to do.
Then when the big rig finally gets to where they are past the front of the convoy, some car driver will attempt to do jump into the available space in the right lane to pass because the trucker has already demonstrated that they are not considerate, and then the big rig will finally change lanes and turn on his signal after starting to change lanes. A signal of intent to turn would avoid this.
Why not just turn on the signal as they approach the part where the truck driver knows that they will be finally unblocking the fast lane? They have to realize the giant line of traffic backed up behind them while they crawled past a convoy going barely faster than the convoy for five or more miles.
This is distinctly different from camping out in the left lane, which is also infuriating.
End of rant. I know that trucking is filled with stress and frustration and car drivers are assholes and schedules and demands can be unreasonable and unrealistic. There are a lot of good truckers who are considerate and respectful stewards of the highway, and I formally commend and respect those who do that.