Mastering the Art of Cost Estimation in Civil Engineering: Analogous vs. Parametric

Analogous and parametric estimating are two standard methods used in civil engineering to estimate the cost and duration of projects.

Analogous estimating?is a top-down approach that compares a new project to similar projects completed in the past. It is often used when there is limited information about the new project, such as in the early planning stages. To develop an analogous estimate, the project manager will identify similar past projects and collect data on their costs and durations. This data is then used to create a range of possible costs and durations for the new project.

Parametric estimating?is a bottom-up approach that uses historical data to develop mathematical relationships between project characteristics and cost or duration. These relationships are then used to estimate the cost or time of a new project based on its specific factors. For example, a parametric estimate for a road construction project might be based on the length of the road, the type of pavement, and the terrain.

When to use analogous estimating:

• When there is limited information available about the new project.
• When the new project is very similar to a past project.
• When analogous estimates have been proven to be accurate in the past.

When to use parametric estimating:

• When there is a significant amount of historical data available.
• When the new project is complex and has many different components.
• When the new project differs from past projects, the mathematical relationships between project characteristics and cost or duration are known.

The extent of applicability to civil engineering projects:

Analogous estimating is widely used in civil engineering projects of all sizes and complexities. It is beneficial for early-stage planning and projects very similar to past projects.

Parametric estimating is also widely used in civil engineering projects, but it is more commonly used for larger and more complex projects. It is also more likely to be used for projects different from past projects but for which the mathematical relationships between project characteristics and cost or duration are known.

Here are some specific examples of when analogous and parametric estimating might be used in civil engineering projects:

Analogous estimating:

• Estimating the cost of a new bridge based on the cost of a similar bridge built recently.
• Estimating the duration of a new road construction project based on the time of a similar road construction project completed recently.
• Estimating the cost of a new wastewater treatment plant based on the cost of a similar wastewater treatment plant that was built recently.

Parametric estimating:

• Estimating the cost of a new highway based on the length of the road, the type of pavement, and the terrain.
• Estimating the duration of a new water distribution project based on the number of miles of pipe to be installed and the type of soil.
• Estimating the cost of a new power plant based on the generating capacity of the plant and the type of fuel used.

In general, parametric estimating is more accurate than analogous estimating, but it requires more data and expertise. Analogous estimating is a good option when there is limited information available or when the new project is very similar to a past project. Parametric estimating is a good option when there is a significant amount of historical data available and when the new project is complex or different from past projects.