When I did Pacific Coast a decade ago, I felt safer on the busy road (below) than on the road in the second photo below because at least the busy road had a good shoulder. The not very busy road was winding and hilly, so traffic behind you might have their vision limited to less than 100 meters, and when you are in and out of shade while the driver behind you is also in and out of bright sun, that does not make for good vision either.



If the driver behind you is at 60 miles per hour, that is 88 feet per second so you do not have very many seconds to be seen.



Some of the brush that was encroaching on the road was thorn bushes, you did not want to get your tires or skin too close.