I don't understand the question.
If I am driving down the freeway in the right lane and I pass an on-ramp with cars travelling down, I shift into the left lane so the car can get over.
If I am driving down the freeway in the right lane and I pass an on-ramp with cars travelling down and I can't get into the left lane, I continue at my current speed since the onus is on the merger to make a safe transition.
If conditions are poor, I am always more cautious and will drive slower.
I would never ever speed up to "let" someone in behind me.
In congestion while travelling slowly, if I am in the right lane and passing an on-ramp with cars travelling down, I leave space between myself and the car in front.
Regardless of anything, if all else fails, it is 100% the onus of the person who is merging onto a freeway, into traffic, or onto an exit to do it safely. This rule has no exception and is without fail.