The Construction Industry Institute (CII) characterizes a megaproject as a complex project exceeding US$1 billion in total installed cost.  They usually involve several complexities, including numerous stakeholders, multiple interfaces, a demanding location, limited access to resources, the use of novel technology, strict regulatory hurdles, large-scale infrastructure demands, teams spread across multiple locations, or considerable impact on political, economic, environmental, or societal landscapes.1Carlos Caldas & Ashish Gupta, Successful Delivery of Megaprojects, Report to the Construction Industry Institute, The University of Texas at Austin, CII Research Report 315-11 § 1.1 (Aug. 2016).X1

Over the past few decades, investors, developers, contractors, and suppliers have expressed growing concern regarding the escalating scale and complexity of major capital projects.  These initiatives often demand substantial long-term capital investment.  They are frequently plagued by recurring challenges, including cost overruns, schedule delays, and a persistent inability to mitigate well-known project risks effectively.  Yet, despite these obstacles, demand for large-scale infrastructure and energy megaprojects endures, with increasingly ambitious outcomes that often outpace the industry’s ability to manage them effectively.

A notable example is the California High-Speed Rail project, which was originally forecasted in 2008 to cost US$33 billion for a 500-mile route linking San Francisco and Los Angeles/Anaheim.2California High-Speed Rail Authority, Business Plan: November 2008, available at https://hsr.ca.gov/wp-content/uploads/docs/about/business_plans/BPlan_2008_FullRpt.pdf.X2  Since then, the project has experienced considerable setbacks, with revised estimates now ranging between US$88.55 billion and US$127.93 billion, and initial operations for a 119-mile segment not anticipated before 2030-2033.3California High-Speed Rail Authority, 2023 Project Update Report, Table 3.7 available at https://hsr.ca.gov/wp-content/uploads/2023/03/2023-Project-Update-Report-FINAL-022823.pdf.X3

Similarly, the expansion of Plant Vogtle in Georgia, through the addition of reactor units 3 and 4, has highlighted the formidable challenges endemic to large-scale nuclear infrastructure.  Initially budgeted at US$14 billion with planned commissioning in 2016 and 2017, the project ultimately exceeded US$30 billion, with commercial operations commencing in July 2023 and March 2024, respectively.4Plant Vogtle Unit 4 begins commercial operation, U.S. Energy Information Administration (May 1, 2024),  https://www.eia.gov/todayinenergy/detail.php?id=61963.X4

In the refining sector, Mexico’s Dos Bocas (Olmeca) refinery, intended to bolster national energy independence, was launched in 2019 with a projected cost of US$8.9 billion and a targeted completion date of 2022.  However, cost estimates have since exceeded US$14.6 billion, with full operational capacity now expected in 2026.5Mexico’s Pemex Requests $6.5 Billion More Funding for ‘Dos Bocas’ Refinery – Documents, Source, U.S. News (Aug. 12, 2022), https://money.usnews.com/investing/news/articles/2022-08-12/mexicos-pemex-requests-6-5-billion-more-funding-for-dos-bocas-refinery-documents-source.X5^{,6RBN Energy LLC, Here I Go Again – Pemex’s Dos Bocas Refinery Still Facing The Startup Blues, Apr.  2024, https://rbnenergy.com/here-i-go-again-pemex-dos-bocas-refinery-still-facing-the-startup-blues.X6}

These examples underscore how megaprojects are often launched with ambitious goals, and are often shaped by political, cultural, and environmental imperatives that sustain them.  

This article examines the history of cost overruns in megaprojects, revealing consistent patterns across infrastructure initiatives in the transportation and oil & gas sectors.  It then explores the industry’s leading explanations for the recurring failures of these projects, especially their tendency to exceed budget forecasts and experience significant schedule delays.

Researchers at Aalborg University in Denmark conducted a landmark study analyzing 258 transport infrastructure megaprojects, collectively valued at nearly US$90 billion (based on 1995 figures).1Bent Flyvbjerg, Nils Bruzelius, & Werner Rothengatter, Megaprojects and Risks: An Anatomy of Ambition at 15 (2003).X1  This was the first major investigation to produce statistically significant insights into the prevalence and magnitude of cost overruns in large-scale transportation ventures.  The study encompassed a wide variety of infrastructure types, including bridges, tunnels, highways, freeways, and rail systems (high-speed, urban, and conventional), spanning 20 countries across five continents.  These projects, both in developed and developing regions, were completed between 1927 and 1998.

By including projects from earlier decades, the research sought to evaluate potential progress in cost estimation accuracy over time, possibly indicating institutional or methodological advancement.  Nonetheless, the findings demonstrated a persistent trend of cost underestimation: in approximately 90% of cases, initial projections fell short, resulting in significant cost overruns.  Rail ventures experienced the most pronounced discrepancies, with actual expenditures exceeding estimates by an average of 45%, followed by tunnels and bridges at 34%, and road projects at 20%.  Across all types, the mean cost escalation was calculated at 28%.2Id. at 15-16.X2

Notably, this pattern emerged as a global phenomenon, with cost overruns documented across all 20 countries in the sample.  While universally present, these discrepancies were notably more severe in developing nations compared to those in North America and Europe.3Id. at 16.X3  The absence of discernible improvements in forecasting accuracy over the 70-year period analyzed suggests a lack of systemic learning,4Id.X4 notwithstanding advancements in project planning methodologies and technologies.  The study ultimately attributed the widespread underestimations not merely to technical errors but to deliberate strategic misrepresentation.5Id.X5

Project advocates often attribute underestimated costs and overstated projected benefits to obtaining funding and approvals, leading projects to be authorized based on overly optimistic assumptions.  As a result, budgetary excesses are frequently managed post-authorization, compounding inefficiencies and intensifying long-term financial risk.

In 2011, Edward W. Merrow of Independent Project Analysis, Inc. (IPA),6Independent Project Analysis, https://www.ipaglobal.com/.X6 shared his findings at the Offshore Technology Conference (OTC) that examined the performance of oil and gas exploration and production (E&P) megaprojects during the first decade of the 21^st century.7Edward W. Merrow, Oil and Gas Industry Megaprojects: Our Recent Track Record, SPE paper No. 153695 accepted for presentation at the Offshore Technology Conference, Houston, 2–5 May 2011, available at https://www.spe.org/media/filer_public/de/15/de15f740-fa58-4ca9-9383-ff54030f990f/153695.pdf.X7  He reported that the success rate of these large-scale initiatives had sharply declined, with only 22% delivering results that could be considered successful.  Projects were deemed unsuccessful if they experienced major deviations from the commitments made at the final investment decision (FID) stage.  In the case of E&P megaprojects, these failures often manifested as cost overruns of 25% and schedule delays averaging 22%.  Merrow also considered project failures those where the first-year production averaged less than 50% of planned production.8Id. at table 4.X8

In 2014, Ernst & Young (EY) undertook a comprehensive evaluation of megaproject performance within the oil and gas industry.9EY Oil and Gas Capital Project Series, Spotlight on Oil and Gas Megaprojects (2014), available at https://www.scribd.com/document/251494380/EY-Spotlight-on-Oil-and-Gas-Megaprojects-2014.X9  The study examined projects with budgets exceeding US$1 billion, including upstream facilities, liquefied natural gas (LNG) plants, pipelines, and downstream refining operations.  Assessments were based on original cost and time estimates, with cost data available for 205 projects and schedule data for 242 projects.  The findings revealed that 64% of these megaprojects experienced cost overruns.  When analyzed by sector, the incidence of overruns was 67% for LNG projects, 64% for pipelines, 62% for downstream operations, and 65% for upstream developments.  On average, the final completion costs were 59% higher than the initial estimates, which translated into a staggering additional cost of US$500 billion across the projects assessed.  Schedule delays were even more prevalent, affecting 73% of the projects overall, including 68% of LNG, 50% of pipelines, 79% of downstream, and 78% of upstream projects.

Numerous other studies and datasets further affirm the widespread occurrence of cost overruns and schedule delays in megaprojects.  While these findings are not included in this article, the core issue remains clear: regardless of facility type or infrastructure sector, megaprojects routinely experience significant deviations from the initial budget and scheduled forecasts.  The following section examines the underlying causes of these persistent challenges.

A. The CII Research Report

In 2013, the CII embarked on a research initiative to identify necessary changes in the planning and execution of megaprojects, aiming to enhance their success rates.  The initial objective was to conduct an extensive literature review to gain a deeper understanding of the practices involved in planning and executing megaprojects.1Successful Delivery of Megaprojects, supra note 1, § 1.X1  As a result, in August 2016, the CII research team produced a comprehensive report outlining the factors that negatively impact the success of megaprojects and providing recommendations to project teams on how to manage and mitigate these factors.

1. Identifying Impact Factors

The CII research team identified 34 impact factors and grouped them into 5 categories.2Id. § 4.5.X2  These factors had a significant occurrence and negatively impacted project performance.  The impact factors were prioritized based on a survey conducted across 35 large projects and 41 megaprojects.3Id. § 5.3.X3  The categories and impact factors are summarized in Table 1 below. 

The types of projects included oil and gas exploration and production, oil refining, mining, power generation, natural gas processing, and heavy industrial.4Id. table 5-1.X4  The approved budgets for large projects ranged from US$100 million to US$750 million, while for megaprojects, budgets ranged from US$1 billion to over US$10 billion.5Id. table 5-2.X5

Table 1 – CII Categories and Impact Factors6Id. table 4-2.X6

 2. Using Industry Data to Quantify Risks in Megaprojects Execution

To fulfill the final objective of its research, the CII team developed a comprehensive tool to assist project teams in identifying and mitigating the impact factors affecting megaprojects.8Id. § 7.X8  A significant feature of the tool is its integration of the industry survey findings.  These findings prioritize the 34 impact factors based on their frequency across surveyed projects, and their average effect on cost, schedule, and business performance.  These ratings help project teams understand which factors have historically had minor, moderate, or serious effects.9Id. § 7.1.X9

The CII research team categorized the frequency of occurrence of impact factors into three distinct groups based on survey data.  Factors falling within the 0 to 33^rd percentile were classified as having low frequency of occurrence, those between the 33^rdand 66^th percentiles as moderate, and those above the 66^th percentile as high frequency.  To evaluate the influence of these factors on project performance, the team applied a severity scale ranging from 0 to 3 across three dimensions: cost, schedule, and business impact.  On this scale, scores between 0 and 1 indicated minor impacts, scores from 1 to 2 reflected moderate impacts, and scores between 2 and 3 represented serious impacts.10Id. § 7.3.2.X10

The analysis of the survey research findings11Id. table 7-1.X11 reveals several critical themes that influence project outcomes. Among the most frequently occurring issues are unplanned changes in key personnel (59%), optimism bias (59%), logistical challenges (49%), multi-location challenges (49%), limited capable contractors (49%) and underperforming contractors (46%).  These factors, while common, vary in their severity of impact.  For example, personnel changes and logistical challenges tend to have moderate cost and schedule impacts, whereas optimism bias and underperforming contractors often lead to more significant disruptions.

Planning and execution deficiencies—particularly those in Category C—emerge as the most damaging to project performance.  Factors such as lack of execution input to front-end planning (FEP), inadequate integrated schedules, and poor risk assessment consistently score the highest in cost, schedule, and business impact, with ratings reaching up to 2.7.  Although these issues are less frequent, their consequences are disproportionately severe, indicating that strategic planning and alignment are essential to mitigating high-impact risks.

Contracting and execution-related issues (Category E) also play a substantial role in project challenges.  Inappropriate delivery strategies, underperforming contractors, and unclear scope definitions in contracts are not only frequent but also carry high impact scores across all dimensions.  These findings suggest that early-stage decisions around contracting and partner selection are pivotal to project success.

Optimism Bias stands out as one of the most critical challenges in mega-projects, with a high frequency of occurrence (59%) and notable impact scores, 2.3 for cost, 2.1 for schedule, and 1.6 for business outcomes.  This cognitive tendency to underestimate risks and overestimate benefits contributes to unrealistic planning assumptions, budget overruns, and schedule delays.  The survey data further reveals a strong correlation between frequency of occurrence and cost/schedule impact, indicating that frequently encountered issues tend to escalate project risks.  However, the most damaging factors often stem from inadequate planning and misaligned execution strategies.  Addressing these through disciplined forecasting, clear scope definition, and effective stakeholder engagement, particularly during front-end planning, can significantly enhance mega-project performance.

B. The OTC Paper

In his 2011 publication presented at the Offshore Technology Conference, Merrow examined the underlying causes of failure in oil and gas E&P megaprojects.  He highlighted three core issues: the incomplete execution of front-end loading (FEL), instability in project leadership, and overly aggressive project schedules.12Oil and Gas Industry Megaprojects: Our Recent Track Record, supra note 13.X12

1. Front-End Loading

FEL is the structured process by which oil and gas projects are planned and designed in stages.  These stages include FEL 0, the initial conceptualization; FEL 1, focused on feasibility assessments; FEL 2, where preliminary designs allow for cost and schedule estimation; and FEL 3, the stage for basic design development.  On a typical project, the end of FEL 3 coincides with the final investment decision (FID).  Projects that are approved proceed to the execution phase, which involves detailed design and construction.  According to Merrow, the success of megaprojects is highly sensitive to the thoroughness of this front-end planning.  He noted that as the completeness and quality of FEL diminishes, the likelihood of cost overruns increases sharply.  For instance, if critical deliverables such as design documents are incomplete at the end of FEL 2 or FEL 3, the estimates generated for cost and schedules are often overly optimistic and unreliable.

2. Instability in Project Leadership

Leadership continuity was identified as another key factor.  Merrow found that the replacement of a project director during execution correlates with a substantial decline, approximately 30%, in the probability of achieving a successful outcome.  Even when FEL quality is maintained, inconsistent leadership undermines coordination, accountability, and strategic direction.

3. Overly Aggressive Project Schedule

Lastly, the paper addressed the industry’s tendency to impose unrealistic timelines.  Using a schedule aggressiveness index, Merrow compared schedules established at the time of the FID to benchmarks from equivalent projects.  An index value above one indicated a more conservative schedule, while a value below one pointed to an overly aggressive timeline.  His research revealed that upstream projects had an average index of 0.90 and a median of 0.87, indicating that schedules were routinely shorter than what was realistically achievable.  Merrow concluded that the relentless push for rapid first oil was not only inflating project costs by tens of billions annually but also negatively impacting production performance after initial startup.

C. The Ernst & Young Study

In its 2014 spotlight on oil and gas megaprojects, EY identified a range of non-technical internal and external factors contributing to project delays and budget overruns.13Spotlight on Oil and Gas Megaprojects, supra note 15.X13  Their analysis uncovered 15 distinct impact factors, systematically grouped into five thematic categories.  These factors reflect challenges in organizational dynamics, governance, and external pressures that commonly derail large-scale initiatives.

Table 2 provides a structured summary of EY’s findings, offering a lens into the patterns that influence performance in complex projects.

Table 2 – Ernest & Young Categories and Impact Factors14Id. figure 7.X14

Despite decades of recurring cost overruns, schedule delays, and familiar root causes, owners and contractors have failed to rectify the persistent underperformance of megaprojects.  Projects continue to grow in scale, complexity, and expense, while often replicating the same mistakes seen in notorious past examples, where costs ballooned well beyond initial estimates and delivery timelines stretched by years.

Advancements in project management practices have made only modest headway in reversing this trend.  Tools and methodologies may have evolved, but their effectiveness is often diluted by the sheer complexity inherent in megaproject delivery.  Studies by CII, IPA, and EY consistently highlight critical factors as recurring drivers of failure.  In particular, inadequate FEL or FEP and overly aggressive project schedules continue to impair outcomes.  Leadership turnover further compounds these issues, undermining strategic continuity and accountability.

Adding to the challenge is the joint venture model common to megaprojects, where culturally and professionally diverse teams must collaborate under intense pressure.  While collaboration is unavoidable and diversity brings valuable perspectives, it can also hinder communication, decision-making, and execution. Studies highlight this misalignment as a major vulnerability, particularly when it is not proactively managed.

Given the persistent challenges facing mega-projects, the focus must shift from trying to eliminate complexity to managing it more effectively.  Rather than expecting flawless execution, success lies in effectively responding to unforeseen challenges.  By embracing pragmatic planning, strengthening risk management, adopting adaptive project frameworks, and building high-performing, culturally agile teams, the industry can reduce vulnerability and improve outcomes.  Acknowledging and adapting to these realities is not just prudent, it is imperative for navigating the complexities inherent in large-scale initiatives.