1 THE HDM-4 TECHNICAL RELATIONSHIPS STUDY Asian Development Bank RETA 5549 Dr. Christopher R. Bennett Team Leader HDM-4 Technical Relationships Study ISOHDM Secretariat University of Birmingham U.K.

2 HIGHWAY DESIGN AND MAINTENANCE STANDARDS MODEL (HDM-III) u Developed by the World Bank and released in 1987 u Used in over 100 countries for different types of investment studies u Predicts pavement performance over time and under traffic and effects of maintenance on pavements u Predicts the effects of pavement and operating conditions on vehicle operating costs (VOC) u Fundamental relationships based on research conducted in Kenya, the Caribbean, India and Brazil

3 DEVELOPMENT OF HDM MODEL

4 LIMITATIONS OF HDM-III u Software difficult to use u Vehicle and tyre technology in the VOC studies different to those of modern vehicles u HDM-III does not consider: u Traffic congestion u Environmental impacts u Rigid pavements u Many types of flexible pavements u Pavement texture and skid resistance u Freeze-thaw conditions u Traffic safety

5 ISOHDM RESEARCH TEAMS

6 STATUS - JANUARY 1996 u ISOHDM Study Accomplishments –Held Inception Workshop in Birmingham UK October 1993 –Held Cold Climate Workshop in Sweden March 1994 –Held International Workshop on HDM-4 in Malaysia November 1994 –Technical Relationships Study completed November 1995 –Held Workshop on Road User Effects at TRL December 1995 –Preliminary Specifications of HDM-4 RUE and RDME Models completed –Programing of software has commenced and some preliminary modules completed –Have established FTP site for accessing material on the Internet

7 HDM TECHNICAL RELATIONSHIPS STUDY (HTRS) u Funded by ADB u Led by N.D. Lea International Ltd. (Canada) u Hosted and supported by Institut Kerja Raya Malaysia (IKRAM) u Other participants: –Works Consultancy Services (New Zealand) –Department of Transport (South Africa) –Van Wyk and Louw (South Africa) –TRL (U.K.) –University of Auckland, University of Pretoria, Michigan Technical Institute –Snowy Mountain Engineering Corporation (Australia) –Various Individuals

8 HTRS RESEARCH APPROACH u Focused on areas deficient in HDM-III u Limited primary research - mainly ‘desk study’ u Evaluated available research results and selecting those most appropriate u Can be summarised as ‘what were the areas where HDM-III needs the most improvement and how could this best be achieved with the available resources’

9 REVIEW OF PREVIOUS EXPERIENCES WITH HDM u Contacted academics, consultants, governments, lending agencies u To date have identified studies in over 100 countries u Used the results to identify the key areas requiring attention in HDM-4 and for preparing draft specifications u Very few studies undertook rigorous calibration/ adaptation of HDM u Summarised parameter values by region and study u Identified alternative models and relationships to those in HDM-III u VOC and RDME results presented in two internal reports

10 KEY ISSUES - RDME u Standardising/Simplifying Data Collection u Generally, one set of models with different parameter values by surface/base materials u Flexible pavements characterised by modified structural number u Uses incremental models developed based on structured empirical approach u Models provided in HDM-4 for –Flexible –Rigid –Block –Unsealed

11 KEY ISSUES - RDME u Extension of Flexible Pavement Deterioration Model –New distresses –Disaggregated distresses to account for individual components –Extended models to account for more diverse construction and climatic effects –Made models easier to calibrate u Rigid pavements –Work conducted by Chile team –Based on USA Ripper Model

12 KEY ISSUES - RDME u Block pavements u Unsealed pavements u Includes models for surface texture and skid resistance u Pavement Maintenance Effects –Covers full range of maintenance practices –More flexible than HDM-III

13 HDM-4 PAVEMENT DISTRESSES u Cracking –Structural –Thermal –Reflection u Disintegration –Ravelling –Delamination –Potholing u Longitudinal Profile –Roughness in IRI m/km u Rutting –Densification –Structural –Plastic Deformation –Wear u Friction –Macrotexture –Skid Resistance

14 INTERACTION OF HDM-4 PAVEMENT DISTRESSES

15 HDM-4 ROAD USER EFFECTS

16 RUE STUDIES

17 REPRESENTATIVE VEHICLES

18 REPRESENTATIVE VEHICLES

19 SPEED PREDICTION u Minor changes to HDM- III Brazil free speed model u Use “3-zone” speed- flow model to consider congestion effects

20 FUEL CONSUMPTION u Replaced HDM-III Brazil model with one based on ARRB ARFCOM model u Predicts fuel use as function of power usage

21 FUEL CONSUMPTION - CONGESTION AND ROAD EFFECTS u Modelling based on ‘acceleration noise’ - standard deviation of acceleration u Comprised of ‘natural’ and ‘traffic’ noise u Natural noise function of slow-moving transport, side friction, roughness u Use Monte Carlo simulation to establish correction factors through calibration routine

22 MAINTENANCE AND REPAIRS u Replaced HDM-III model with linear model u Linear model easier to calibrate and parameter values provided for Brazil and India u Significant reduction in roughness effects for passenger cars and light vehicles u Increased roughness effects for heavy buses u No benefit on parts from reducing roughness below 3 IRI m/km

23 CAPITAL COSTS u Using Chesher and Harrison Optimal Life (OL) method u Uses maintenance cost stream to determine OL u Model calibrated by supplying target OL and adjusting age exponent in parts model

24 OTHER RUE COMPONENTS u Tyre Consumption –Extending HDM-III mechanistic model to cover full range of tyre types u Oil Consumption –Adopting South African model u Overheads and Utilisation –Changes to methods from HDM-III u Traffic Safety –Using matrix approach u Effects of road works on users u Noise and Vehicle Emissions

25 SUPPORTING STUDIES u Swedish Study –Tyre consumption –Emissions –Speed-flow –Cold-climate pavement deterioration u Japanese Team –Slow-moving transport