You're overthinking it. Drivers will just continue to do what they (mostly) already did. If they need to pass a cyclist, or a person walking along the road, or whatever, and there isn't enough room in the lane, they will cross the centerline when it's safe to do so. In fact, the first part of this bill is changing the existing law so that this behavior is now explicitly legal:

>If it is not possible to overtake a vulnerable user, as defined in section 1 of chapter 90, or other vehicle at a safe distance in the same lane, the overtaking vehicle shall use all or part of an adjacent lane, crossing the centerline if necessary, when it is safe to do so.