STUDY ON THE IMPROVEMENT OF THE DESIGN AND COST ESTIMATION SYSTEM FOR PUBLIC WORKS IN JAPAN

Abstract

 In setting the ceiling price for public works, it is important to ensure fair profits for the contractor in addition to the cost necessary to meet the required performance of the construction work. However, inconsistencies between design documents and the site conditions and the client estimates that is not consistent with the actual conditions are cited as major issues. This study focuses on the design and cost estimation of the Ministry of Land, Infrastructure, Transport and Tourism, which represents the client estimates in Japan, and analyzes the relationship between the bidder's estimate and the client's estimate, and the situation in which the client’s cost estimation standards affect construction. It has been confirmed that the tender process for tunnel and dam construction, which compete on advanced technologies, is akin to a "game of guessing the minimum price" determined by the client. In many cases at the construction stage, the construction method described in the client cost-estimation standard was prioritized. To solve these problems, we have considered ways to flexibly utilize the client cost-estimation standards and proposed some cost estimation methods that can accommodate various construction methods including new technologies and ensure construction safety and fair profits for contractors.