Excellent response to my concerns, G. Cornelius.
Much obliged.
I’ve heard these called escape lanes.
No, because they are not directly entering traffic; the ramp opens onto the hard shoulder, so they can match speed there before entering the traffic flow.
Service stations in the UK are now just like airports (but without the planes), incorporating all manner of shops, restaurants and services.
Escape lanes are reasonably common in very hilly areas; there are quite a few of them on the main routes down to the West Country, particularly where there is a steep slope down into a populated area.