THE WAY FORWARD

or

WHO SAID RESEARCH WAS EASY ?

Relationship between variablesRelationship between variables

x

Y = (say) roughness after 5 years

Poor

Good

Expectation for acceptable performance

Relationship between variablesRelationship between variables

x

Y = (say) roughness after 5 years

Poor

Good

Relationship between variablesRelationship between variables

x

Y = (say) roughness after 5 years

Poor

Good

Relationship between variablesRelationship between variables

x

Y = (say) roughness after 5 years

Poor

Good

Multi-value problemMulti-value problem

Plasticity Index

Y = (say) roughness after 5 years

Poor

Good

Multi-value problemMulti-value problem

Plasticity Index

Y = (say) roughness after 5 years

Poor

Good

Multi-value problemMulti-value problem

Plasticity Index

Y = (say) roughness after 5 years

Very dry

Very wet

Poor

Good

High traffic (conventional)High traffic (conventional)

traffic leveltraffic level subgrade strengthsubgrade strength base typebase type base layer thicknessbase layer thickness base layer strength (for some types)base layer strength (for some types) sub-base layer thicknesssub-base layer thickness sub-base typesub-base type surface layer thicknesssurface layer thickness surface typesurface type climateclimate

33

33

33

33

22

33

22

33

33

33

26,24426,244

THE ROAD DESIGN OR “RISK” ENVIRONMENTTHE ROAD DESIGN OR “RISK” ENVIRONMENT

PREVAILING CLIMATERainfall (intensity, distribution)Temperature (evaporation & diurnal change)Future change or unpredictability

DRAINAGE AND HYDROLOGYGround & surface water flowHydro-genesisDemand of terrainModifying influences

AVAILABLE MATERIALSAlternative & thin bituminous surfacingsPavement materials

•Marginal materials•Standards

•Subgrade & road formation•Problem soils•Moisture sensitivity•Stabilisation options and treatments

GEOMETRICS AND CROSS-SECTION PROFILESRoad widthCrown heightDemand of terrainSealed shoulders

TRAFFIC CHARACTERISTICSAxle loadingTyre pressuresSeasonalityPositionGrowth projections

OTHERTechnology solution

•labour based•Intermediate equip

•Safety•Institutional environment capacity•Financing•Political pressure•Design period•Road side activity

MAINTENANCECapacity & skillsFundingProgramming

CONSTRUCTIONQuality controlCapacity, training & experienceSelection and use of plantInfluence of construction traffic

CONSTRAINTS OF THE “GREEN” ENVIRONMENTConstrained alignmentsAccess to materialsDepletion of resourcesTerrain stability

OPTIMUM OR APPROPRIATE

PAVEMENT DESIGN

METHODOLOGY

Pass/fail criteriaPass/fail criteria

Strength of material

Specification for trunk road

Number ofsamples

Low traffic Low traffic traffic leveltraffic level subgrade strengthsubgrade strength base typebase type base layer thicknessbase layer thickness base layer strength (for all types)base layer strength (for all types) sub-base layer thicknesssub-base layer thickness sub-base typesub-base type surface layer thicknesssurface layer thickness surface typesurface type climateclimate technologytechnology maintenancemaintenance cross section and geometrycross section and geometry drainage drainage ++++

33

33

66

33

33

33

33

33

44

33

22

22

44

33

2 million at least2 million at least

BASIS FOR THE ORN31 BASIS FOR THE ORN31 DESIGNSDESIGNS

Full scale design and performance Full scale design and performance experiments carried out by TRL in experiments carried out by TRL in tropical countriestropical countries

Full scale design and performance Full scale design and performance experiments carried out by others in experiments carried out by others in tropical countriestropical countries

Performance studies of as-built networksPerformance studies of as-built networks Empirically based performance modelsEmpirically based performance models

(eg Highway Design Model III )(eg Highway Design Model III ) Theoretical / mechanistic analysisTheoretical / mechanistic analysis

X

How do we cope ?How do we cope ?

Engineering judgementEngineering judgement

Engineering judgementEngineering judgement

we cannot do without itwe cannot do without it but it is all too easy to draw but it is all too easy to draw

incorrect conclusions so...incorrect conclusions so... one man’s judgement is not one man’s judgement is not

enoughenough we need to know about we need to know about

variability and reliabilityvariability and reliability to do so we need lots of data to do so we need lots of data

WEIGHTED EQUIVALENT ESA APPLICATIONS

103 104 105 106 107 108

EQUIVALENT THICKNESS De, INCHES45

40

35

30

25

20

10

5

0

15

xx

x

xxx x x

xxxxxx

xx

x x xx

xxx

x

x

xx

x

xx x x

xx

xxx xx

x

xx

x

x

AASHO "DESIGN" EQUATION COMPARED WITH DATA

Engineering judgementEngineering judgement

we cannot do without itwe cannot do without it it is all too easy to draw incorrect it is all too easy to draw incorrect

conclusions so...conclusions so... one man’s judgement is not enoughone man’s judgement is not enough to evaluate risk we need lots of data to evaluate risk we need lots of data

consensus necessary - an expert systemconsensus necessary - an expert systemhence this projecthence this project

The way forwardThe way forward

As the projects proceeds there will be As the projects proceeds there will be many issues to be addressedmany issues to be addressed

this meeting has been the ‘literature this meeting has been the ‘literature review’ (as it were)review’ (as it were)

the projects are clearly very ambitious the projects are clearly very ambitious and there is a danger of failing to focus and there is a danger of failing to focus sufficiently on the most important issues sufficiently on the most important issues

we now need to begin to synthesize our we now need to begin to synthesize our experiences to help inform the data experiences to help inform the data collection phasecollection phase

A few observationsA few observations

Variability and improving Variability and improving technologytechnology

do not knock beltsdo not knock belts andand bracesbraces specifications can get tighter and specifications can get tighter and

better as contractors improvebetter as contractors improve there are usually several ways to there are usually several ways to

solve a problem solve a problem it may be unnecessary to agonise it may be unnecessary to agonise

over which is best - they may be over which is best - they may be equally (or almost equally) cost equally (or almost equally) cost effectiveeffective

on the other hand they may not !!!on the other hand they may not !!! so don’t waste money (John Hine)so don’t waste money (John Hine)

And eventually we will need to And eventually we will need to decide how to present the final decide how to present the final

outputoutput

Catalogue of structures?Catalogue of structures? GraphsGraphs ?? Think about itThink about it

The end for nowThe end for now

Consideration of the Road Design Environment for LVSR’s

OPTIMUM OR APPROPRIATE

PAVEMENT DESIGN

PREVAILINGCLIMATE

PREVAILINGCLIMATE

AVAILABLE MATERIALSAVAILABLE MATERIALS

TRAFFIC CHARACTERISTICSTRAFFIC CHARACTERISTICS

CONSTRUCTIONCONSTRUCTION

CONSTRAINTS OF THE “GREEN”

ENVIRONMENT

CONSTRAINTS OF THE “GREEN”

ENVIRONMENT

MAINTENANCEMAINTENANCE

OTHERSOTHERS

GEOMETRICS AND

CROSS-SECTION PROFILES

GEOMETRICS AND

CROSS-SECTION PROFILES

DRAINAGE AND HYDROLOGYDRAINAGE AND HYDROLOGY

DRAINAGE AND HYDROLOGYDRAINAGE AND HYDROLOGY

Ground waterGround water Surface waterSurface water Drainage designDrainage design Permeability of pavement layersPermeability of pavement layers Surface infiltrationSurface infiltration Hydro-genesisHydro-genesis

CLIMATECLIMATE

Rainfall (intensity, distribution)Rainfall (intensity, distribution) Temperature (evaporation & diurnal Temperature (evaporation & diurnal

change)change)

CONSTRUCTIONCONSTRUCTION

Technology and selection and use of Technology and selection and use of plantplant

Quality control and realistic variabilityQuality control and realistic variability Influence of construction traffic (intensity, Influence of construction traffic (intensity,

distribution)distribution)

MAINTENANCEMAINTENANCE

Capacity and skillsCapacity and skills FundingFunding Programming (likely timing)Programming (likely timing)

MATERIALSMATERIALS

Alternative & thin bituminous surfacings Alternative & thin bituminous surfacings Pavement materialsPavement materials

Marginal materialsMarginal materials StandardsStandards

Subgrade & road formationSubgrade & road formation Problem soilsProblem soils Moisture sensitivityMoisture sensitivity Stabilisation options and treatmentsStabilisation options and treatments

GEOMETRICS AND GEOMETRICS AND CROSS-SECTION PROFILES CROSS-SECTION PROFILES

Road widthRoad width Sealed shoulders or notSealed shoulders or not Embankment heightEmbankment height CamberCamber

TRAFFICTRAFFIC

Axle loadingAxle loading Tyre pressuresTyre pressures SeasonalitySeasonality Position on carriagewayPosition on carriageway Vehicle typesVehicle types NMTNMT Growth Growth