Earthwork must have been computed at least once before baking is available, since the bake reads the computed earthwork sections.
▪
Baking exists for staged, multi-road design: bake road A once it is final, then design road B on the resulting terrain so its earthwork and cross-sections correctly account for road A already being there.
▪
Unbake Road reverts to the terrain as it stood immediately before the most recent bake. The pre-bake snapshot is kept until you bake again or click Make Permanent, which discards it.
▪
Until a road is baked, anything in cut sits below the opaque terrain in the 3D view unless the X-ray option is used.