Estimating costs accurately at the early concept and feasibility design stages is challenging, especially for transport and civil engineering infrastructure projects. Here’s why:
Limited information: At this stage, the project definition is often vague, with only conceptual drawings and sketches, incomplete technical specifications, and undefined materials and construction methods. This lack of detail makes calculating precise quantities and labour requirements difficult, impacting cost estimations.
Unforeseen circumstances: Early feasibility studies involve exploring various options and configurations. Potential risks and unknowns are high, like geological surprises during excavation or unpredictable market fluctuations affecting material prices. Accurately factoring in such uncertainties at this stage is nearly impossible.
Unrefined design elements: Assumptions and approximations become prevalent due to insufficient data. Structural components, construction techniques, and even the final project footprint might change significantly as the design progresses. Cost estimates based on preliminary assumptions can quickly become outdated and inaccurate.
Estimating methodologies: Traditional cost estimation methods like historical data or per-unit pricing often falter at the early stage. These methods rely on well-defined project details, which aren’t readily available during concept development.
So, what are the best solutions to appraise transport and civil engineering infrastructure schemes at this early stage? Here are some strategies:
1. Range estimates: Instead of aiming for a single cost figure, provide a range with high and low boundaries. This acknowledges the inherent uncertainties and offers flexibility for decision-making.
2. Parametric cost models estimate costs based on crucial project parameters like length, capacity, or complexity. While not as detailed as later-stage estimates, they offer a faster and more dynamic approach for comparing different options at the concept stage.
3. Early contractor involvement: Engaging experienced contractors early on can be valuable. Their expertise in construction methods and material pricing can provide valuable insights for refining the design and making more realistic cost estimations.
4. Sensitivity analysis: Analysing how the cost estimate changes with variations in critical parameters helps understand the main cost drivers and identify potential risks. This information can be used to prioritise design decisions and mitigate cost escalations later.
5. Software tools: Several specialised software tools exist for early-stage cost estimation in infrastructure projects. These tools can incorporate parametric models, historical data, and project-specific information to generate more accurate and informed cost ranges.
Ultimately, acknowledging the limitations of early-stage cost estimates is crucial. The focus should be on providing decision-makers with a realistic range of possible costs, identifying potential risks, and prioritising design choices that optimise value within the expected cost range. By employing the abovementioned strategies, you can navigate the initial uncertainties and make informed decisions for your transport or civil engineering infrastructure project, even at the early design stage.