One of the most powerful features of Excel is the Data Table function. In pavement design, traffic forecasts are notoriously unreliable. A sophisticated spreadsheet can run a sensitivity analysis, generating a table showing how pavement thickness requirements change as traffic growth rates vary from 5% to 10%. This allows engineers to plan for contingencies rather than relying on a single deterministic number.
| Criteria | Manual/Calculator | Expensive Software | | |----------|------------------|--------------------|----------------------| | Speed | Slow | Fast | Fast | | Cost | Free | $1,000+ | Free / Low cost | | Transparency | Low | Black box | Full formulas visible | | Flexibility | High | Low | High (you can modify) | | Auditability | Hard | Medium | Easy (cell-by-cell) |
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This remains the most common basis for Excel tools. The core equation solves for the Structural Number ($SN$), which represents the load-carrying capacity required. A spreadsheet handling this method must organize the following inputs:
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