If driverless cars eliminated the need for public transport (in the contemporary sense) you could open up rail corridors to create highways for cyclists, joggers, and walkers - it would open up alternatives to motorised travel.

Or you could turn the theory on its head - use the rail corridors as motorised transport arteries and open up the roads to the bipeds.

(From Sydney where the rail network is extensive - I'd imagine places with less ubiquitous rail wouldn't benefit as much)