1 The HDM Approach to Multi- Year Programming Christopher R. Bennett University of Auckland Highway and Traffic Consultants Ltd.

2 Definitions Treatment –A maintenance activity e.g. reseal, shape correction Strategy –A treatment and when it is applied, e.g. reseal every 6 years; shape correct at 5 IRI m/km

3 HDM Approach

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5 HDM - Summary Predicts pavement deterioration Predicts vehicle operating costs Predicts impact of maintenance on pavement condition Determines total transport costs for strategy

6 Example of HDM Analysis

7 Analysis Approaches HDM-III: –‘Life Cycle Cost’ analysis - also called ‘Total Transport Cost’ analysis HDM-4 –‘Life Cycle Cost’ analysis –‘Budget Period’ analysis

8 Life Cycle Costing Adopting higher engineering or maintenance standards reduces user and possible administration costs By considering the total costs over extended periods one can establish investment programme which minimises the total transport costs

9 Life Cycle Cost Analysis Consists of defining a series of strategies Have a ‘do minimum’ strategy e.g. routine maintenance and patching Applied as base case and the merit of different strategies assessed relative to base case Each section analysed over extended period under maintenance strategies

10 LCC Analysis - Disadvantages Can take a long time to run for large networks Optimising over long period difficult –How accurate are the traffic forecasts? –How accurate are the pavement deterioration predictions? –How certain are we that future maintenance will be performed when required?

11 Budget Period Analysis Simplification which uses shorter time period (typically 5 years) Work done in the budget period becomes ‘do something’; deferred until after the budget period ‘do minimum’ Need to account for residual value of investment after budget period and benefits accruing after budget period

12 Budget Period Analysis Benefits

13 BP Analysis - Assumptions Maintenance after budget period will be less effective than during budget period Pavement performance after budget period similar for both alternatives –No need to calculate VOC or deterioration past first year after budget period

14 Hierarchy of Applications Strategic –Macro Level Requirements and Standards Project –Detailed Study of Individual Road Programming –Combining Projects into Rolling Work Programme

15 Network Strategy Analysis... Long term budget forecasts Maintenance Rehabilitation Improvement Development Bridges TOTAL

16 Network Condition Forecasts

17 Analysis Procedure Segment network into homogeneous sections Should use dynamic sections and concurrent transformations

18 Fixed vs Dynamic Sections

19 Concurrent Transformations

20 Analysis Procedure... Define series of strategies For each section: –Predict pavement deterioration and maintenance effects –Predict VOC –Determine TTC

21 Evaluation For each section have costs and benefits for each strategy Combine strategies for network and optimise under budget constraints Review and adjust programme