Principles of Calibrating HDM-4 Dr. Christopher R. Bennett chris@htc.co.nz

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

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

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

Importance of Data

Information Quality Levels (IQL)

Adapting Local Data to HDM-4

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

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

Calibration Adjustments

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

Hierarchy of Effort

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

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

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

Bias and Precision

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

Sensitivity Classes

RDWE - Bituminous Pavement Sensitivity Ranking

Outcomes Most Affected

RUE Calibration

For Further Information A guide to calibration and adaptation Reports on various HDM calibrations from: www.htc.co.nz