Why not add a shoulder only on those places where a cyclist would not be visible from 100 yds behind. This would allow a car to pass safely when it comes to a cyclist, rather than having to do an emergency brake if there is oncoming traffic. This would require less construction work, and reduce the impingement on peoples front yards, but would require more survey work and planning.
100 yds visibility would give a 40 mph car over 10 secs to slow down to avoid a collision with a 12 mph bicycle