horns & bells are for pedestrians IME, not cars.

>> properly segregated infrastructure for each class of vehicle.

I ride a lot in traffic and the problem with segregated infrastructure (i.e. bike lanes) is the interfaces and constriction. Pedestrians step off the sidewalk or out of cars into constrained bike lanes all the time and there's no where to go; cars turn across bike lanes with the same problem.

You can't always do it, but if you can eliminate the speed differential I believe riding in traffic is much safer than a bike lane, at least until you get enough bike volume to keep drivers aware. THat's hard to do in most of NA or year round.