THE WAY FORWARD or WHO SAID RESEARCH WAS EASY ?

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

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

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

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

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

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

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

High traffic (conventional) Ò traffic level Ò subgrade strength Ò base type Ò base layer thickness Ò base layer strength (for some types) Ò sub-base layer thickness Ò sub-base type Ò surface layer thickness Ò surface type Ò climate ,244

THE ROAD DESIGN OR “RISK” ENVIRONMENT 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 AVAILABLE MATERIALS Alternative & thin bituminous surfacings Pavement materials Marginal materials Standards Subgrade & road formation Problem soils Moisture sensitivity Stabilisation options and treatments GEOMETRICS AND CROSS-SECTION PROFILES Road width Crown height Demand of terrain Sealed shoulders TRAFFIC CHARACTERISTICS Axle loading Tyre pressures Seasonality Position Growth projections OTHER Technology solution labour based Intermediate equip Safety Institutional environment capacity Financing Political pressure Design period Road side activity MAINTENANCE Capacity & skills Funding Programming CONSTRUCTION Quality control Capacity, training & experience Selection and use of plant Influence of construction traffic CONSTRAINTS OF THE “GREEN” ENVIRONMENT Constrained alignments Access to materials Depletion of resources Terrain stability OPTIMUM OR APPROPRIATE PAVEMENT DESIGN METHODOLOGY

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

Low traffic Ò traffic level Ò subgrade strength Ò base type Ò base layer thickness Ò base layer strength (for all types) Ò sub-base layer thickness Ò sub-base type Ò surface layer thickness Ò surface type Ò climate Ò technology Ò maintenance Ò cross section and geometry Ò drainage Ò million at least

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

How do we cope ? 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

WEIGHTED EQUIVALENT ESA APPLICATIONS EQUIVALENT THICKNESS De, INCHES x x x x xxxx xx x xx x x x xxx x x x x x x x x x x xxx x x x xxx x x x x x x AASHO "DESIGN" EQUATION COMPARED WITH DATA

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 u consensus necessary - an expert system u hence this project

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

A few observations

Variability and improving technology  do not knock belts and braces  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)

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

The end for now

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

 Ground water  Surface water  Drainage design  Permeability of pavement layers  Surface infiltration  Hydro-genesis

CLIMATE  Rainfall (intensity, distribution)  Temperature (evaporation & diurnal change)

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

MAINTENANCE  Capacity and skills  Funding  Programming (likely timing)

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

GEOMETRICS AND CROSS-SECTION PROFILES GEOMETRICS AND CROSS-SECTION PROFILES  Road width  Sealed shoulders or not  Embankment height  Camber

TRAFFIC TRAFFIC  Axle loading  Tyre pressures  Seasonality  Position on carriageway  Vehicle types  NMT  Growth