Comparing Gross and Net Additions to Material Stock for Roadways in Japan

The overall material stock of the Japanese economy is growing. Large portion of the stock is invested in construction materials such as asphalt, cement, sand and gravel, crushed stone, and other aggregates. The transport sector, particularly roadways, accounts for a large proportion of the construction material stock. This paper evaulates the Gross Additions to Stock (GAS) and Net Additions to Stock (NAS) in Japan’s roadways using novel measures derived directly from stock. Consistent with previous studies, Economy-Wide Material Flow Accounting (EW-MFA) is used as the conceptual framework. Annual GAS is estimated from data on the improvement, maintenance and new extension of roads and pavements, excluding highways. NAS is alternatively estimated on a five year average using total stock. Calculations show that in 2005, GAS for roadways in Japan is 61m tons, while NAS was approximately half of this amount (33m tons). The results of this paper show that while annual GAS and NAS have reduced, total roadway stock has increased over the study period from 754 million tons to 2 billion tons (1970-2005). The implications of these results and the use of GAS and NAS as indicators of sustainability are discussed.