THE WAY FORWARD

1. THE WAY FORWARD or WHO SAID RESEARCH WAS EASY ?

2. Relationship between variables Y = (say) roughness after 5 years Poor Expectation for acceptable performance  Good x

3. Relationship between variables Y = (say) roughness after 5 years Poor   Good x

4. Relationship between variables Y = (say) roughness after 5 years Poor    Good x

5. Relationship between variables Y = (say) roughness after 5 years Poor    Good x

6. Multi-value problem Y = (say) roughness after 5 years Poor   Good Plasticity Index

7. Multi-value problem Y = (say) roughness after 5 years Poor   Good Plasticity Index

8. Multi-value problem Y = (say) roughness after 5 years Poor   Very wet  Very dry Good Plasticity Index

9. High traffic (conventional) • 3 • 3 • 3 • 3 • 2 • 3 • 2 • 3 • 3 • 3 • 26,244 • traffic level • subgrade strength • base type • base layer thickness • base layer strength (for some types) • sub-base layer thickness • sub-base type • surface layer thickness • surface type • climate

10. THE ROAD DESIGN OR “RISK” ENVIRONMENT TRAFFICCHARACTERISTICS Axle loading Tyre pressures Seasonality Position Growth projections PREVAILING CLIMATE Rainfall (intensity, distribution) Temperature (evaporation & diurnal change) Future change or unpredictability DRAINAGE AND HYDROLOGY Ground & surface water flow Hydro-genesis Demand of terrain Modifying influences MAINTENANCE Capacity & skills Funding Programming GEOMETRICS AND CROSS-SECTION PROFILES Road width Crown height Demand of terrain Sealed shoulders CONSTRAINTS OF THE “GREEN” ENVIRONMENT Constrained alignments Access to materials Depletion of resources Terrain stability OPTIMUM OR APPROPRIATE PAVEMENT DESIGN METHODOLOGY • OTHER • Technology solution • labour based • Intermediate equip • Safety • Institutional environment capacity • Financing • Political pressure • Design period • Road side activity • AVAILABLE MATERIALS • Alternative & thin bituminous • surfacings • Pavement materials • Marginal materials • Standards • Subgrade & road formation • Problem soils • Moisture sensitivity • Stabilisation options and treatments CONSTRUCTION Quality control Capacity, training & experience Selection and use of plant Influence of construction traffic

11. Pass/fail criteria Number of samples Specification for trunk road Strength of material

12. Low traffic • 3 • 3 • 6 • 3 • 3 • 3 • 3 • 3 • 4 • 3 • 2 • 2 • 4 • 3 • 2 million at least • traffic level • subgrade strength • base type • base layer thickness • base layer strength (for all types) • sub-base layer thickness • sub-base type • surface layer thickness • surface type • climate • technology • maintenance • cross section and geometry • drainage • ++

13. BASIS FOR THE ORN31 DESIGNS • Full scale design and performance experiments carried out by TRL in tropical countries • Full scale design and performance experiments carried out by others in tropical countries • Performance studies of as-built networks • Empirically based performance models (eg Highway Design Model III ) • Theoretical / mechanistic analysis X

14. How do we cope ? Engineering judgement

15. Engineering judgement • we cannot do without it • but it is all too easy to draw incorrect conclusions so... • one man’s judgement is not enough • we need to know about variability and reliability • to do so we need lots of data

16. 103 104 105 106 107 108 EQUIVALENT THICKNESS De, INCHES 45 x 40 x x x x x x x 35 x x x x x x x x x x x x x x x 30 x x x x x x x 25 x x x x x x x x x x 20 x 15 x 10 x x 5 0 WEIGHTED EQUIVALENT ESA APPLICATIONS AASHO "DESIGN" EQUATION COMPARED WITH DATA

17. Engineering judgement • we cannot do without it • it is all too easy to draw incorrect conclusions so... • one man’s judgement is not enough • to evaluate risk we need lots of data • consensus necessary - an expert system • hence this project

18. The way forward • As the projects proceeds there will be many issues to be addressed • this meeting has been the ‘literature review’ (as it were) • the projects are clearly very ambitious and there is a danger of failing to focus sufficiently on the most important issues • we now need to begin to synthesize our experiences to help inform the data collection phase

19. A few observations

20. Variability and improving technology • do not knock beltsandbraces • specifications can get tighter and better as contractors improve • there are usually several ways to solve a problem • it may be unnecessary to agonise over which is best - they may be equally (or almost equally) cost effective • on the other hand they may not !!! • so don’t waste money (John Hine)

21. And eventually we will need to decide how to present the final output • Catalogue of structures? • Graphs • ? • Think about it

22. The end for now

23. Consideration of the Road Design Environment for LVSR’s PREVAILING CLIMATE DRAINAGE AND HYDROLOGY AVAILABLE MATERIALS GEOMETRICS AND CROSS-SECTIONPROFILES OPTIMUM OR APPROPRIATE PAVEMENT DESIGN TRAFFICCHARACTERISTICS OTHERS MAINTENANCE CONSTRUCTION CONSTRAINTS OF THE “GREEN” ENVIRONMENT

24. DRAINAGE AND HYDROLOGY • Ground water • Surface water • Drainage design • Permeability of pavement layers • Surface infiltration • Hydro-genesis

25. CLIMATE • Rainfall (intensity, distribution) • Temperature (evaporation & diurnal change)

26. CONSTRUCTION • Technology and selection and use of plant • Quality control and realistic variability • Influence of construction traffic (intensity, distribution)

27. MAINTENANCE • Capacity and skills • Funding • Programming (likely timing)

28. MATERIALS • Alternative & thin bituminous surfacings • Pavement materials • Marginal materials • Standards • Subgrade & road formation • Problem soils • Moisture sensitivity • Stabilisation options and treatments

29. GEOMETRICS AND CROSS-SECTION PROFILES • Road width • Sealed shoulders or not • Embankment height • Camber

30. TRAFFIC • Axle loading • Tyre pressures • Seasonality • Position on carriageway • Vehicle types • NMT • Growth