1. Principles of Calibrating HDM-4
Dr. Christopher R. Bennett

2. Reliability of Results Depends On:
How well the available data represent the real conditions to HDM
How well the model’s predictions fit the real behaviour and respond to prevailing conditions

3. Data vs Calibration
Need to appreciate importance of data over calibration
If input data are wrong why worry about calibration?

4. Application of Model Input Data
Must have a correct interpretation of the input data requirements
Have a quality of input data appropriate for the desired reliability of results
Calibration
Adjust model parameters to enhance the accuracy of its representation of local conditions

5. Importance of Data

6. Information Quality Levels (IQL)

7. Adapting Local Data to HDM-4

8. Calibration Focus Road User Effects
Predict the correct magnitude of costs and relativity of components - (Data)
Predict sensitivity to changing conditions - (Calibration)
Road Deterioration & Works Effects
Reflect local pavement deterioration rates and sensitivity to factors
Represent maintenance effects

9. RUE - Impact of Calibration
Observed v. HDM-III defaults before calibration - case in Canada
Adjust components first
Check total VOC by vehicle type for reasonableness

10. Calibration Adjustments

11. Calibration Levels Level 1: Basic Application Level 2: Calibration
Addresses most critical parameters
‘Desk Study’
Level 2: Calibration
Measures key parameters
Conducts limited field surveys
Level 3: Adaptation
Major field surveys to requantify relationships
Long-term monitoring

12. Hierarchy of Effort

13. Level 1 - Application Required for ALL HDM analyses
Once-off ‘set-up’ investment for the model
Mainly based on secondary sources
Assumes most of HDM default values are appropriate

14. Level 2 - Calibration
Makes measurements to verify and adjust predictions to local conditions
Requires moderate data collection and moderate precision
Adjustments entered as input data, typically no software changes

15. Level 3 - Adaptation Comprises Structured research, medium term
Advanced data collection
Evaluates trends and interactions by observing over long time period
May lead to alternative local relationships

16. Bias and Precision

17. What to Focus On
HDM-III had about 80+ data items and model parameters; HDM-4 has more.
Sensitivity of each item has been classified by sensitivity tests
Don’t worry about less-sensitive items

18. Sensitivity Classes

19. RDWE - Bituminous Pavement Sensitivity Ranking

20. Outcomes Most Affected

21. RUE Calibration

22. For Further Information
A guide to calibration and adaptation
Reports on various HDM calibrations from: