Surface evidence
Roadway Drag Factor Calculators
Derive a surface value from field testing instead of relying on a generic published range.
Method overview
drag factor = resisting force ÷ test weight
CrashCompute includes separate worksheets for drag-sled pulls, controlled test skids, measured deceleration, roadway grade, and wet or icy surface adjustments.
Evidence to document
- Calibrated test equipment and total test weight.
- Repeated pulls or skid runs across the relevant travel path.
- Surface, temperature, moisture, tire, and vehicle conditions.
- Roadway grade and the direction of travel.
Limitations
A drag factor is specific to the tested conditions. Report the range and repeatability of the field measurements rather than only the average.
Record measurements, assumptions, units, rounding, and source material so another investigator can reproduce the result. See the methodology and validation center for verification policy and citation guidance.
Related tools
Test-skid worksheet · Deceleration to drag factor · Skid mark speed