In Texas, functional obsolescence includes:

Nearby highway noise is an example of external obsolescence (also called economic or locational obsolescence), not functional obsolescence, because the source of value loss is entirely outside the property's boundaries and beyond the owner's control — it originates from the surrounding environment rather than the property's own design.

Deferred maintenance refers to physical deterioration — specifically, the curable type where the owner has postponed necessary repairs — and is categorized under physical depreciation rather than functional obsolescence, because the value loss stems from the physical condition of existing components rather than from design deficiencies.

Economic decline of the area is a classic example of external obsolescence, where broader neighborhood or regional economic forces (such as plant closures, population decline, or rezoning of adjacent land) reduce property values from outside the property — this is entirely distinct from functional obsolescence, which is always an internal property characteristic.