Interesting situation. My question would be why is there one lane with
no one in it? Does that lane end further down the road and merge
to the left to get on the highway or does it go somewhere else?

Either way the engineering group who designed that ramp made
2 lanes so that it could be occupied by vehicles making the left turn
into that lane. Depending on where that lane is headed after the turn
is made the decision on the part of the person occupying the middle
lane has the right to decide to merge safely into the left lane at any
point the merge can safely be done.

In fact it is recommended that the driver make the merge further
down the middle lane so as to not slow down traffic behind the driver.

It is the responsibility of other drivers to be courteous and not
get angry when other drivers legally use other lanes in order not
to get in a line that will clearly obstruct traffic as the diagram clearly
shows would have occurred.

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