Building Information Modeling (BIM) has set up a mark in the construction industry over a decade. In order to gain benefit of BIM in estimating the project cost at the early stage of construction with the limited data available, a new concept of MacroBIM has been introduced in the industry. However, limited amount of research has been implemented to determine how MacroBIM has been accepted in the construction industry. Most research was focused on the accuracy of the conceptual estimation. This research attempted to determine the effectiveness of MacroBIM process applied at early stages of construction for conceptual cost estimation. Experts from the discipline of architecture, contractor and owners were interviewed and their professional opinions on MacroBIM were analyzed using grounded theory. The results show that, compared to the traditional conceptual estimating process, MacroBIM is an effective method for 1) saving labor hours, 2) conveying assumptions with the help of its visualization capabilities, 3) enhancing the collaboration among the project participants, and 4) evaluating multiple design scenarios. However, fear of using MacroBIM and trust in its outcome existed among some contractors, architects, and owners because this technology has not matured yet. Moreover, the need of interoperability between the MacroBIM tools and MicroBIM tools, such as Revit, has also surfaced in the study.

Conceptual cost estimates play a crucial role on initial project decisions although scope is not finalized and very limited design information is available during early project stages. At these stages, cost estimates are needed by the owner, contractor, designer or the lending organization for several purposes including / determination of feasibility of a project, financial evaluation of a number of alternative projects or establishment of an initial budget. Conceptual cost estimates are not expected to be precise, since project scope is not finalized and very limited design information is available during the pre-design stages of a project. However / a quick, inexpensive and reasonably accurate estimate is needed based on the available information. In this study, conceptual cost estimating models will be developed for urban railway systems using data of projects from Turkey. The accuracy of the models and advantages of the study will be discussed.