I'm a big fan of turning some existing roads into cyclist and local access only roads, and then discouraging extended biking on other roads. Tunnels could certa

I'm a big fan of turning some existing roads into cyclist and local access only roads, and then discouraging extended biking on other roads. Tunnels could certainly be part of that. In general, I don't think it's ever going to be safe for bikes and cars to share the same roadway any more than it would be for cars and pedestrians to travel on the same surfaces. For short distances, sure, but not on big arterial routes where everybody is at war with everyone else all the time.