The Road Formation is the surface of finished earthworks on which a road pavement is constructed. It includes the earthworks, the general shaping of the road and basic drainage, but excluding stormwater infrastructure.
Image: NSW State Archives - (CC BY 4.0) licence
The Glossary of Austroads Terms defines the "formation" as "the surface of finished earthworks, excluding cut or fill batters."
The International Financial Reporting Standards require that major parts (significant components) of assets be separately identified and depreciated. This has been interpreted to mean that the road formation should be separately valued & depreciated.
Road formations are typically depreciated over a very long period, but Interpretation 1055 Accounting for Road Earthworks suggests that some but not all road earthworks do not have a limited useful life, and don't need to be depreciated.
The useful life of a road formation will vary considerably due to a wide range of environmental factors.
The table below shows the useful life for road formations adopted by Councils or published elsewhere. At the time of writing a useful life of 1000 years seems to be typical.
| Council | Adopted Life |
|---|---|
| Camden Council | 999 years |
| Hume City Council | 1000 years |
| Muswellbrook Shire Council | 1000 years |
| Wollondilly Shire Council | 1000 years |
| Bundaberg Regional Council | 150 years |
| Whittlesea City Council | ∞ years |