Time planning and estimating in megaprojects – why do they fail?

Megaprojects consistently face challenges delivering on time, a problem recognized across multiple sectors. This study addresses the persistent issue of inaccurate and unrealistic time estimates during the early phases of megaproject development. Through a multiple-case study of two Norwegian state-funded construction projects, the paper investigates how and when reliable time estimates can be produced in the project lifecycle. Both projects went through the Norwegian Quality Assurance scheme (Concept review, QA1, and QA2) The main finding is that early-stage time estimates, particularly during the Concept and QA1 phases, are often based on rough approximations with minimal documentation and limited analytical rigor. The QA2 stage provides more refined estimates yet remains prone to uncertainty due to the evolving project scope and inadequate contractor involvement. These insights suggest that current quality assurance regimes prioritize cost over time, often neglecting uncertainty analysis for time planning. In this paper, we address the following question: How are initial time estimates in megaprojects developed, and how can their accuracy and reliability be assessed? And at what stage in the project lifecycle is it possible to produce a realistic and reliable estimate of the project’s duration? This research advances prior work by revealing specific weaknesses in the Norwegian QA system’s treatment of time estimates and by demonstrating the value of forward-looking planning models and time-based uncertainty margins. The study contributes to improved governance of megaprojects by underscoring the need for structured time estimation equivalent to that used for cost.