Where I live there are no shoulders and often a big deep ditch instead. There are very few passing zones as most roads are a series of short punchy hills. The lanes are also very narrow.
I tried a visibility experiment. The only thing that worked fantastic was an orange jumper suit that looks very much like the local prison garb. Riding a fat bike with flags. I could not believe the amount of room they gave met but ultimately decided not to ride dressed like that. .