In the last couple of weeks, I have three times faced the same issue.
All the traffic has merged successfully as the left lane ends. Someone, in each of these cases a big van or 4WD, decides to jump in the left lane and floor it. When they have no room left in the left lane/shoulder, they just pull right with no blinker even. Now a sensible driver identifies the DH, and is ready to give way to might just for safety sake, but I have seen drivers caught out when they have been forced onto the wrong side of the road by the DH pulling out when right next to them.
The DH then progresses till the next slow vehicle lane about three places in front of where they could (should) have been.
Sometimes there is justice however. I was driving on Northern Rd recently, when an impatient tradie and a small Hyundai were both trying this and jostling with each other as well. They both pushed past me at well over the speed limit, probably about 30 to 40 k over.Obviously they had somewhere important to be in a hurry. The Hyundai had the upper hand, but the tradie kept looking in and outside for any chance to pass. What for I don't know, and a long line of traffic ahead were progressing smoothly at close to the speed limit. My grandson was in the car, and even he commented on the aggressive behaviour of the tradie.
The next overtaking lane (junction of Elizabeth Drive) started just on a double lane roundabout. The tradie (at this point just in front of me) was quicker and started into the left lane using the shoulder before it actually started. The Hyundai was incensed and blasted his horn and gestured at the tradie. Anyhow, with the advantage and a lengthy overtaking lane, he was off and speeding away. The Hyundai got caught in traffic and must have been annoyed as hell, at least in the short term.
About halfway along the overtaking lane, I rounded a curve to note that the tradie up ahead was at the end on the overtaking lane. The fact that I was on the speed limit the whole way indicates the speed he must have reached. It was dusk, but I noted a vehicle suddenly pull out from a private property driveway up ahead. I thought to myself, "Wouldn't it be good if that was a police car".
Well, next I saw the flashing lights come on. What a great opportunity to discuss safe driving and courtesy on the road with my grandson.
It is also not just merging that could be better done. On a double lane road, how many cars keep an eye on cross roads to see if they can move lanes to allow cars entering from the side a better chance to move. I regularly see drivers do the opposite. Change lanes to block the entrant, and then move back to their original lane.
I have spent some considerable time in a European country where the drivers do all sort of mad things. However, courtesy seems to prevail and because of that it works.