Rail, like buses, only really works if one train or bus will do the journey. Changing train or bus adds so much time it makes commutes silly, with the added jeopardy of missed connections if one is late.
When I left an office job in Oxford to become a driving instructor, this left my partner with a dilemma. Not being able to drive (long story, best for all of us that she didn't), she needed to use buses. Bus at the bottom of the road goes direct to Oxford bus station. All good so far, but whilst she worked in the hospitals, with good bus services, timings did not fit well, changing a 40 minute car commute into a 90-120 minute bus journey.
She looked at Swindon. Again the bus at the bottom of the road goes direct, but again, timings did not fit.
So she took early retirement, and filled a few years doing simpler local jobs.
I think the French 'priority a droite' is variable, with signs to show when it is in operation. I'm not sure whether the default 'is' or 'not', would have to review this if I travel there again.
M40 at its northern end, where it joins the M42 below Birmingham, slips in from the right if travelling East. This can be exciting when the traffic is flowing well. When busy, it slows a lot, and joining is a little less stressful, although if heading to the NEC one then needs to get across all 4 lanes quite soon, otherwise you'll be past the back of the queue.
I seem to remember a slip road off to the right on the M8 in Glasgow. Quite enjoyed that one.