Accident reduction from self-driving vehicles is more likely than any significant road change/widening. Ever look at where oncoming drivers are focused?
People get distracted and they make human mistakes, forgiveness lies in road width and the time and space it affords. Last year I went to Florence to meet a buddy well before dawn, foggy along an invisible road as yet uncluttered with visible striping by DOT.
Jumping jesus, it was terrifying, it also turned into a crappy day on the river.
I hate 126.