Atrios's new bugaboo it seems. He's right that we won't get there so long as there isn't something that forces us to. That is, that last 1% (or 0.1%...) can probably only come from mandated full implementation of autonomous vehicles. The issues/problems he describes are due to human drivers. If all cars are autonomous and speak to each other (via street grid) then all of those things either go away or can be dealt with.
Of course, that type of mandate won't happen until a critical mass of vehicles out there are "Autonomous-ready" and that isn't likely to happen in my lifetime.