When delivery schedules go wrong: what are the root causes?

Estimated reading time: 4 minutes


The timely delivery of initiatives is a critical benchmark for success. Unfortunately, a pervasive issue across various sectors, ranging from infrastructure to defence projects is the head in your hands scenarios of consistent failure of schedules. This article delves into the causes behind schedule delays, shedding light on the root factors that contribute to projects falling behind their intended timelines.

When schedules go wrong

A study conducted by Ernst and Yong showed that the average Canadian infrastructure project runs 39% over budget and is behind schedule by an average of 12 months. This isn’t just about infrastructure projects; we see the same issues in defence. It’s also not just applicable to large government projects. The same schedule issues that plague these projects are the same ones that are delaying our home renovation projects, that kitchen redo we’ve been wanting to do or building that deck in the backyard.

Root causes of schedule delay

Why do these schedule delays really happen and what are those root causes of those delays? According to Bent Flyvbjerg in his paper, ‘Over Budget, Over Time, Over and Over Again: Managing Major Projects‘, he suggests that the root causes of schedule delays can be separated into three main categories.

1. Bad luck or error

The first category of reasoning is one that we’re certainly all familiar with and we’ve likely heard as reasoning for delays in the past, just plain old bad luck. While an explanation like this is probably all too common, granted once in a blue moon, bad luck really is to blame. For example, COVID-19 was a truly unforeseen circumstance that completely derailed project delivery timelines across the globe. But ultimately bad luck does not hold up to statistical analysis and testing.

2. Optimism bias

What the data tells us is that project planners tend to underestimate the risks of complexity and scope changes during those early project development stages, this underestimation or ignorance of risks is called optimism bias. When we’re in the grips of optimism bias, you make decisions based on a delusional optimism rather than on a rational weighting of gains, losses and probabilities. You overestimate the benefits and underestimate costs and time; this is just part of the problem. The data tells us that optimism bias while explaining some of this doesn’t explain everything. If optimism bias is the psychological explanation as to why schedules can be delayed, then strategic misrepresentation is the political explanation.

3. Strategic misinterpretation

Project planners, politicians and stakeholders can deliberately overestimate benefits and underestimate costs and schedule for strategic purposes, this is to get that project off the ground and get that early approval and funding. There are strong incentives that exist in those early project approval stages to present the project as favourably as possible, really emphasising those benefits and de-emphasising any potential risks. One of Flyvbjerg’s conclusions in this area is that these two explanations, optimism bias and strategic misrepresentation, they work to complement one another. Optimism bias has more merit where political and organisational pressures are low, where a strategic misrepresentation has its merit when those types of pressures are especially high. Both are important to understand when we’re trying to explain bias and schedule delay in procurement projects.

Impact of schedule delays

What are some of the significant and wide-ranging negative impacts that can occur from these constantly delayed schedules? You all know schedule delays almost always result in increased costs, and increasing costs which can damage stakeholder relationships. This includes clients, suppliers, subcontractors, even regulatory bodies. Another impact to consider is negative public perception helping to erode the public’s confidence in the government’s ability to delivery important projects on time and the government’s ability to manage public funds effectively. Think of those that are running these large projects internally that are in the headlines for the wrong reasons and have constant schedule delays, it can be demoralising for hardworking project teams. That constant pressure to meet a deadline coupled with the frustration of knowing that you’re not going to meet that deadline can have quite a negative effect on morale leading to higher staff turnover and potentially the loss of skilled workers. Unsurprisingly, there is a litany of impacts that are negative from delayed schedules.


The challenges surrounding schedule delays in projects can be attributed to an array of different of factors. The first, an occasional victim to unpredictable circumstances, while acknowledged, falls short under the scrutiny of statistical analysis. The second, a more pervasive issue termed ‘optimism bias,’ reveals a tendency among project planners to underestimate the risks during early development stages. Complementing this psychological explanation is the third factor – ‘strategic misrepresentation,’ a deliberate act by planners and stakeholders to paint a rosy picture to gain approval.

As these causes intertwine, their repercussions resonate far beyond the project timeline. Escalating costs strain stakeholder relationships, tarnishing public perception and eroding confidence in the government’s project management capabilities. The domino effect extends internally, breeding demoralisation among project teams and fostering higher staff turnover. Recognising these influences is imperative for effective project delivery and management.

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