1. Henry Kerali Lead Transport Specialist The World Bank
Introduction to HDM-4
Henry Kerali
Lead Transport Specialist
The World Bank

2. Transport and Development
Transport sector is vital for economic & social development
Roads constitute the largest component of transport
Roads require a balance of:
Maintenance (or Preservation)
Development (or Improvement)
Objective of Road Management
Consistent and Rational Policy Objectives
Sufficient and Reliable Funding
Effective Procedures & Management Tools

3. Economic basis for selecting investment alternatives
HDM-4 Objectives .
Economic basis for selecting investment alternatives
Road standards
Pavement standards
Alignments

4. HDM-4 Objectives ..
Standard framework for investigating road investments
Minimize Road Agency and Road User Costs
Non-motorized transport facilities
Traffic congestion
Vehicle emissions
Travel times
Transport costs
Road accidents

5. History of the HDM model
2000
ISOHDM
RTIM
(TRRL)
RTIM2
(TRL)
RTIM3
The first move towards producing a road project appraisal model was made in 1968 by the World Bank. The first model was produced by MIT following a literature survey and was based mainly on a framework proposed by de Weille. The resulting Highway Cost Model (HCM) highlighted areas where more research was needed to provide a model that was more appropriate to developing country environments with additional specific relationships.
Following this, TRRL, in collaboration with the World Bank, undertook a major field study in Kenya to investigate the deterioration of paved and unpaved roads as well as the factors affecting vehicle-operating costs in a developing country. The results of this study were used by TRRL to produce the first prototype version of the Road Transport Investment Model (RTIM) for developing countries. In 1976, the World Bank funded further developments of the HCM at MIT that produced the first version of the Highway Design and Maintenance Standards model (HDMII).
Further work was undertaken in a number of countries to extend the geographic scope of the RTIM and HDM models, including; the Caribbean Study by TRRL which investigated the effects of road geometry on vehicle operating costs, the India Study by the Central Road Research Institute which studied particular operational problems of Indian roads in terms of narrow pavements and large proportions of non-motorised transport, and the Brazil Study funded by UNDP, which extended the validity of all of the model relationships.

6. HDM-4 Concept Predicts road network performance as a function of
Traffic volumes and loading
Road pavement type and strength
Maintenance standards
Environment / Climate
Quantifies benefits to road users from:
Savings in vehicle operating costs (VOC)
Reduced road user travel times
Decrease in number of accidents
Environmental effects
The HDM-4 analytical framework is based on the concept of pavement life cycle analysis. This is applied to predict the following over the life cycle of a road pavement, which is typically 15 to 40 years:
Road deterioration
Road work effects
Road user effects
Socio - Economic and Environmental effects
Once constructed, road pavements deteriorate as a consequence of several factors, most notably:
Traffic loading
Environmental weathering
Effect of inadequate drainage system

7. Optimum Transport Costs
Total
Optimum
Road User
Road Works
Design Standards

8. Road Management Purpose: Typical objectives:
To optimise the overall performance of the network over time in accordance with POLICY OBJECTIVES and within budgetary constraints
Typical objectives:
Minimise transport costs
Preserve asset value
Provide and maintain accessibility
Provide safe and environmentally friendly transport
1. Another way of defining the purpose would be ‘to maintain and improve the existing road network to enable its continued use by traffic in an efficient, safe and environmentally appropriate manner’.

9. Life Cycle Costs Road Agency Costs Road User Costs
Management, Operations
Labor, Equipment, Materials
Land acquisition
Maintenance and Rehabilitation
Road User Costs
Vehicle operation
Travel time
Road accidents
1. The cost components are self explanatory. Each item will be costed using “ECONOMIC PRICES” not “MARKET PRICES”. To ensure the analysis is correct all costs in the project will be at a given date and exclude taxes .
2. The proportions of labour and machinery costs will depend upon the choice of technology chosen for the project. Labour intensive projects are often specified by lending agencies and governments these will obviously use less machinery and more labour than a capital intensive project.
3) Land. It maybe that land will need to be acquired for the road construction. Where land cannot be put to any other use (e.g.. For a road crossing a desert) its economic value will be zero but land clearly has a value if it can be used for farming or housing or industrial use.

10. Comparison of Project Alternatives
Discounted RAC
(Road works + RUC)
Project Life (years)
End of
Analysis
Without
Overlay
NPV
With Overlay

11. Comparison of Project Alternatives
Discounted RAC
Without
Paving
NPV
RUC
Cost of Paving
Project Life (years)
End of
Analysis

12. Life Cycle Analysis Predict Road Deterioration
Input Data
Predict Road Work Effects
Repeat
for all
years
VOC, Accident & Time costs
Discount Annual Costs & Compare
Output NPV, IRR,..

13. Road Deterioration Predict long term pavement performance
Predict effects of maintenance standards
Calculate annual costs: Road Agency + Road User
Poor
Maintenance Standard
The figure illustrates the predicted trend in pavement performance represented by the riding quality that is often measured in terms of the international roughness index (IRI). When a maintenance standard is defined, it imposes a limit to the level of deterioration that a pavement is permitted to attain. Consequently, in addition to the capital costs of road construction, the total costs that are incurred by road agencies will include the periodic maintenance, or rehabilitation works applied during the life of a pavement. These in turn depend on the standards of maintenance and improvement specified by HDM-4 users.
Road Condition
Pavement
Performance
Curve
Rehabilitation
Good
Time (years) or Traffic Loading

14. Pavement Performance Pavement Types modelled:
Bituminous (AC, ST, etc.)
Unsealed (Gravel, Earth, Sand, etc.)
Concrete (JPCP, JRCP, CRCP, etc.)
Block (Bricks, etc.)
Models from pavement performance experiments in:
Brazil, Kenya, India, South Africa
France, USA, Sweden, Finland, Australia
The overall long-term condition of road pavements directly depends on the pavement type and strength, traffic loading, the environment and the maintenance or improvement standards applied to the road. The rate of pavement deterioration is directly affected by the standards of maintenance applied to repair defects on the pavement surface such as cracking, ravelling, potholes, etc., or to preserve the structural integrity of the pavement (for example, surface treatments, overlays, etc.), thereby permitting the road to carry traffic in accordance with its design function.
The pavement deterioration models in HDM-4 are based on models derived from results of large scale field studies carried out in Brazil, Kenya, South Africa, Sweden and Australia.

15. Principles Of Deterioration Models
Models are structured empirical
Individual distresses modelled separately
Relationships are incremental and recursive
dY = K a0 f(X1, X2, X3, etc)
Modelled sequentially through to roughness
Maintenance intervention at end of each year
1. Empirical - based on observed performance of roads.
Structured - variables included in the relationships are based on theoretical
understanding; i.e. mechanistic behaviour of pavements.
2. Each distress modelled separately; e.g.cracking, rutting etc.
3. Incremental - change in magnitude rather than absolute.
Recursive - year on year (possibly seasonal in future).
4. Distresses are inter-related; e.g. cracks let in more water which means that
road roughness will increase at a greater rate. Hence there is a logical order
in which the computer models the various distresses.
5. At the end of each year, maintenance interventions are applied.
These might reset the value of a distress.
Next year the model applies the incremental change to this value.

16. Cracking Initiation Model
ICA=Kcia{CDS2*a0exp[a1SNP+a2(YE4/SN2)+CRT}
ICA time to cracking initiation, in years
CDS construction quality
SNP structural number of pavement
YE4 traffic loading
Kcia calibration factor
CRT effect of maintenance

17. All Cracking Progression
CRP = retardation of cracking progression due to preventive treatment
Progression of All cracking commences when tA > 0 or ACAa > 0

18. Pavement Deterioration Concept1
Water
ingress
Further
cracking
Patches
Shear
Uneven
surface
Spalling
Faster
deformation
ROUGHNESS
Potholes
Time
Surface
Lower strength
Area of
Cracking
Rut
depth

19. Concrete Roads Models From USA Chile Joint Spalling Punch outs
Cracking
Faulting
Slab failures
Riding Quality
Models From
USA
Chile

20. Bituminous Pavements Predicted defects: Cracking Ravelling Edge Break
Potholes
Riding Quality
Skidding

21. Bituminous Road Deterioration .

22. Bituminous Road Deterioration ..

23. Unsealed Roads

24. Unsealed Road Deterioration ..

25. Unsealed Road Deterioration …

26. Road Work Classification
Preservation
Routine
Patching, Edge repair
Drainage, Crack sealing
Periodic
Preventive treatments
Rehabilitation
Pavement reconstruction
Special
Emergencies
Winter maintenance
Development
Improvements
Widening
Realignment
Off-carriageway works
Construction
Upgrading
New sections

27. Road Works

28. Road Work Effects
Condition
Reconstruct
Overlay
Traffic / Time 10

29. Road User Effects

30. RUE Components MT Vehicle operating costs (VOC)
MT Travel time costs (TTC)
NMT Time and operating costs (NMTOC)
Accident costs (AC)
RUE = RUC + Emissions + Energy + Noise
RUC = VOC + TTC + NMTOC + AC

31. Road User Effects Vehicle operating costs Travel time Road accidents
fuel, oil, tyres, parts consumption
vehicle utilisation & depreciation
Travel time
passengers
cargo
Road accidents
Non-Motorized Transport
Energy consumption
Vehicle emissions & noise
The impacts of the road condition, as well the road design standards, on road users are measured in terms of road user costs, and other social and environmental effects. Road user costs comprise:
Vehicle operation costs (fuel, tyres, oil, spare parts consumption; vehicle depreciation and utilisation, etc.),
Costs of travel time - for both passengers and cargo, and
Costs to the economy of road accidents (that is, loss of life, injury to road users, damage to vehicles and other roadside objects).
The social and environmental effects comprise vehicle emissions, energy consumption, traffic noise and other welfare benefits to the population served by the roads. Although the social and environmental effects of often difficult to quantify in monetary terms, they can be incorporated within the HDM-4 economic analyses if quantified exogenously.
Note that in HDM-4, road user effects can be calculated for both motorised transport (motorcycles, cars, buses, trucks, etc.) and non-motorised transport (bicycles, human powered tricycles, animal pulled carts, etc.).

32. RUE Features in HDM-4
Effects of traffic congestion on speed, fuel, tyres and maintenance costs
Non-motorised transport modelling
Effects of road works on users
Traffic safety impact
Vehicle emissions impact
Vehicle noise impact

33. Motorised Vehicles

34. Impact of Road Condition on VOC
Heavy Truck
Bus
Road User Costs ($/veh-km)
Pickup/utility
The figure illustrates the impact of road condition (represented in terms of the IRI) on the operating costs of different types of vehicles. Road User Costs in HDM-4 are calculated by predicting physical quantities of resource consumption and then multiplying these quantities by the corresponding user specified unit costs. It is necessary to ensure that the vehicle resource quantities predicted are in accordance with the range of values observed in the area of application.
Car
Rickshaw
Good
Road Condition (IRI)
Poor

35. Non-Motorised Transport

36. Role of HDM-4
1. Will be discussing the details of the different applications of HDM-4 in later sessions, but this provides an overview. HDM-4 is a decision support system and helps us with the above functions.
2. Note that HDM-4 only has its own database developed specifically for the various analyses which it carries out. It is not a road management system, or pavement management system, in its own right although data can be imported from such systems for use in HDM-4.

37. Road Management Functions
Planning
Setting standards and policies
Long term estimates of expenditure
Programming
Medium term work programmes
Preparation
Detailed project design and work packaging
Operations
Implementation of works in field
1. These are fairly self explanatory but the trainers should develop typical brief examples from their own countries.
Planning - setting standards, broad network, not spatial (e.g. we are concerned with the issue ‘$x spent on the national network over the next y years would result in z% of the network having a roughness less than...’
Programming - works programmes at network level (1,5 year programmes etc)
Preparation - detailed designs and work packages
Operations - managing the work and scheduling work, monitoring costs etc

38. HDM-4 Applications Road sector policy studies
Strategic planning of road network development, improvement & maintenance
Determination of funding requirements
Preparation of multi-year road work programmes
Economic appraisal of individual road projects
Research studies
Road pricing
Vehicle regulations
Pavement design standards

39. Standards & Policies Road pricing Vehicle regulations
road use costs (to define fuel levies)
congestion charges
weight-distance charges
Vehicle regulations
axle load limits
energy consumption, vehicle emissions & noise
Engineering Standards
sustainable road network size
pavement design and maintenance standards

40. Strategy Analysis Objectives:
Analysis of entire road networks to determine funding needs and predict performance under budget constraints
Objectives:
Determine budget allocations for road maintenance and improvement
Prepare work programs
Determine long term network performance
Assess impact on road users 2

41. Strategic Analysis Approach
Road Network G F P
Matrix H M L
Preservation Evaluation
Resource Constraints
Revenues, Sector budgets
Development Candidates
Optimal Strategy under Budgetary Constraints
Optimization Module

42. Effect of budget levels
Primary Roads
Annual Budget
$10m
$15m
$20m
Target = 3.5 IRI

43. Road Network Performance
Budget Allocations
Feeder
Roads
$30m/yr
Secondary
Roads
$35m/yr
Primary
Roads
$20m/yr

44. Budget Scenario Analysis

45. Optimal budget requirements

46. Programme Analysis
Preparation of single or multi-year expenditure programs under specified budget constraints.
Objective: prioritise candidate road projects in each year within annual budget constraint
Annual budgets obtained from strategic maintenance plan

47. Procedure .
Use specified standards to screen network & identify candidate projects, e.g.
road sections which exceed specified condition
roads with inadequate capacity
pavements which need strengthening
upgrade pavements with high traffic volumes

48. Procedure .. Determine maintenance or improvement options
Specify budget limits & periods
Optimise using selected objective
Produce optimal list of projects for budget period

49. Work Programme Output
2003
2004
2005

50. Project Appraisal Project types Economic indicators
New construction, upgrading
Reconstruction, resealing
Widening, lane addition
Non-Motorised Transport lanes
Economic indicators
Net Present Value (NPV)
Economic Rate of Return (ERR)
Benefit Cost Ratio (BCR), NPV/C
First Year Rate of Return (FYRR)

51. Project Level Outputs Sensitivity analysis results Scenario analysis
Road condition indicators
Road user cost details
Energy & emissions

52. HDM Technology Set
Knowledge
Base
Software
Models
SEE
RDWE
RUE

53. HDM Series

54. Conclusions – Why HDM-4? Transparency of analysis
Life cycle analysis capable of:
Short, Medium & Long term analyses
What-if analysis
Internationally accepted analysis framework
Availability of technical expertise
Local calibration

55. http://hdm4.piarc.org http://www.bham.ac.uk
Web sites: