Planning

There is a peculiar characteristic shared by almost every project plan ever written: it is too optimistic. Not because the people who write project plans are dishonest, but because the human brain is structurally inclined to underestimate time, cost, and complexity when imagining future work. The psychologist and Nobel laureate Daniel Kahneman called this the planning fallacy, the tendency to predict that our own projects will proceed close to their best-case scenario even when we know from experience that things rarely do (Kahneman, 2011). Understanding the planning fallacy is not a reason to stop planning; it is a reason to plan more carefully and build in the margin that optimism will otherwise eat.

Why it matters

Planning is where strategy becomes schedule, and schedule becomes commitment. A project plan answers the questions that stakeholders, funders, and team members need answered before they will invest their trust, their money, or their time: What are we doing? How long will it take? What does it need? What could go wrong? Without a credible plan, those questions don't go away, they just get answered informally, inconsistently, and often wrongly.

For a small Irish charity managing a funded programme with quarterly reporting requirements, or an SME delivering a contract on fixed terms, the quality of the project plan directly determines whether deliverables arrive on time, whether relationships with funders survive the delivery process, and whether the team emerges with its motivation intact. Planning is not administrative overhead; it is the principal act of project leadership in the early stages of a project.

Core concepts

The most important concept in project planning is scope, the agreed boundary that separates what the project will deliver from what it will not. Scope definition is where most planning failures start, because scope that is vaguely stated at the beginning of a project will be interpreted differently by every person who reads it, and those different interpretations will eventually collide. The Work Breakdown Structure (WBS) is the standard tool for turning a vague scope statement into something concrete: it decomposes the project deliverable into smaller and smaller components until each component is manageable, estimable, and assignable (PMI, 2021). A WBS is not a schedule, it does not show sequence or timing, but it is the foundation on which the schedule is built.

Scheduling connects the WBS components to time and sequence. The critical path method (CPM), developed in the 1950s on US Navy and construction projects and now embedded in virtually every project management software package, identifies the sequence of dependent activities that determines the minimum possible project duration (Kelley and Walker, 1959). Activities on the critical path have no float, any delay in them delays the whole project. Activities off the critical path have float, meaning they can slip by some amount without affecting the final delivery date. For a small project manager, the practical implication is clear: monitor the critical path obsessively and accept some latitude on everything else.

Resources, people, budget, time, and equipment, are the constraints within which a plan has to work. Resource levelling is the process of adjusting the plan so that resources are not over-allocated at any given point. In a lean organisation where three people are doing the work of six, resource levelling quickly reveals that some things need to be sequenced rather than run in parallel, and that the aggressive timeline the sponsor wants is physically impossible without trade-offs. This conversation is better had at planning stage than at week eight.

Kahneman's work on the planning fallacy suggests a practical remedy: the reference class forecast, which involves asking not "how long will this specific project take?" but "how long have similar projects taken in the past?" (Kahneman, 2011). Kahneman and Amos Tversky found that people systematically ignore base rates, the actual distribution of outcomes for comparable projects, in favour of optimistic projections about the specific case in front of them. Simply asking "what percentage of projects like this have come in on time and under budget?" and adjusting accordingly is one of the most evidence-based improvements any planning process can make.

PMI's project planning processes also include the management plan, the meta-document that governs how scope, schedule, cost, quality, communications, risk, and procurement will each be managed throughout the project (PMI, 2021). For a small organisation, writing a full management plan for every project is disproportionate. What the concept provides is a useful checklist of the questions worth asking: How will we communicate? Who approves scope changes? How will we track budget?

The Irish context

Project planning in Ireland has a well-documented and persistent infrastructure challenge. The National Development Plan 2021–2030, which commits €165 billion in public capital investment over the decade, has been characterised by significant cost overruns and schedule slippage in major infrastructure projects, a pattern repeated from Metro North to the National Children's Hospital, whose final cost exceeded initial estimates by a factor of several times (Department of Public Expenditure and Reform, 2021). These are not just government failures; they reflect fundamental challenges in estimating complex, long-term, multi-stakeholder projects that are highly susceptible to scope creep, regulatory change, and optimism bias.

For Irish SMEs and charities operating at a much smaller scale, the planning lessons are the same but the consequences are more immediate and more personal. A community project that runs six months over schedule does not make the evening news, but it depletes the volunteer goodwill that makes future projects possible. A funded programme that exceeds its budget by 20% without warning does not get pulled, but it damages the funder relationship that was years in the making.

Local Enterprise Offices offer business planning and project management training across Ireland, including direct mentor support for businesses developing their first formal project plans (Local Enterprise Office, 2024). Enterprise Ireland's Business Accelerator and management development programmes build planning capability at the level of scaling companies. These supports are specifically designed for the Irish SME context, resource-constrained, often technically competent but operationally informal organisations that need structured planning support rather than enterprise-scale methodology.

Common pitfalls

Three failures dominate. The first is planning to the best case. Schedules built without contingency, budgets with no reserve, and resource plans that assume every person will be available every day are not optimistic, they are fiction. Industry guidance typically recommends a management reserve of 5–15% of budget and schedule for projects with moderate uncertainty (PMI, 2021). The second is planning without the people doing the work. A project plan created by management and handed to a team is likely to be resented and less accurate than one co-created with the team. The people doing the work usually have the best estimates of how long the work takes. The third is treating the plan as finished. A project plan is a baseline, not a prophecy. Regular replanning, updating the plan based on what has actually happened, is not an admission of failure; it is good practice.

Watch / Listen / Read

Watch, The puzzle of motivation by Dan Pink (TED2009, 18 min). Pink's research on what actually drives performance, autonomy, mastery, and purpose rather than traditional carrots and sticks, is essential context for any project planner who wants their team to execute rather than just comply. Planning that ignores human motivation produces schedules that people comply with but don't care about. Available at https://www.ted.com/talks/dan_pink_the_puzzle_of_motivation.

Listen, Projectified® by PMI covers project planning practices across multiple episodes. Available at https://www.pmi.org/projectified-podcast; search "planning" or "scheduling" for relevant conversations with practitioners on scope definition and schedule management.

Read, Kahneman, D. (2011) Thinking, Fast and Slow. London: Penguin. Chapters 23–24 address the planning fallacy, optimism bias, and the reference class forecasting method in accessible detail. The most important book for project planners who want to understand why their plans consistently underestimate.

Quick quiz

1. What name did Kahneman give to the human tendency to predict projects will proceed close to best case even when experience says otherwise?
2. What does WBS stand for, and what is its primary purpose in project planning?
3. What does the critical path method (CPM) identify in a project schedule?
4. What does Kahneman's proposed "reference class forecast" involve?
5. Approximately how much public capital investment does Ireland's National Development Plan 2021–2030 commit?

Answers: (1) The planning fallacy. (2) Work Breakdown Structure, it decomposes project scope into manageable, estimable components. (3) The sequence of dependent activities that determines the minimum possible project duration. (4) Asking how long similar past projects actually took and adjusting estimates accordingly. (5) €165 billion.

References

Department of Public Expenditure and Reform (2021) National Development Plan 2021–2030. Dublin: Government of Ireland. Available at: https://www.gov.ie/en/publication/774e2-national-development-plan-2021-2030/ (Accessed: 27 April 2026).

Kahneman, D. (2011) Thinking, Fast and Slow. London: Allen Lane.

Kelley, J.E. and Walker, M.R. (1959) 'Critical-Path Planning and Scheduling', in Proceedings of the Eastern Joint Computer Conference, Boston, pp. 160–173.

Local Enterprise Office (2024) Business planning and mentoring supports. Available at: https://www.localenterprise.ie/ (Accessed: 27 April 2026).

Project Management Institute (2021) A Guide to the Project Management Body of Knowledge (PMBOK® Guide) (7th edn). Newtown Square, PA: PMI.