To elaborate on this, camera based lane keeping systems are readily available and generally work well if the lane markings are in good enough condition and aren't obscured by snow.

A signal embedded in the pavement wouldn't be subject to wear, but it would make adjusting lanes much more difficult (if you've driven in the bay area, you've probably noticed lane lines moved back and forth for construction pretty regularly) and it would actually be worse in the snow/ice --- a consensus lane appears which may not follow the marked alignment, and following the marked alignment would involve driving over accumulated snow and ice.

I agree completely. Putting a guide wire in the road would be spending a lot of money to (incompletely) solve a problem that’s already been solved.

The point is that (primarily) the road needs to be smart, not the car. There should ideally be a synergy between the car and road, but the road has to be the primary vector to guide the car.