Since the first release of HDM-4 the software has been used in many countries on a diverse range of projects. During these projects many users have provided feedback on the usability and functionality of the software. The analysis of these comments drove the initiative to further develop and improve HDM-4. Many of the technical models used in the software have also been extensively reviewed in the light of new research and data. This review identified improvements to the technical models implemented within HDM-4.
The improvements that are included in the Version 2.0 release of HDM-4 are categorized and listed below. A brief description of the improvements follows this list.
For exisiting users of HDM-4 a guide to getting started with HDM-4 Version 2 is available to download.
Budget Scenario Analysis
Multi-Criteria Analysis (MCA)
Estimation of Social Benefits
Updated Database Technology
Redesign of New Section Facilities
Bituminous Road Deterioration
Bituminous Work Effects
Unsealed Road Deterioration
Unsealed Work Effects
Road User Effects
Intervention Editor & Work Item Triggering Logic
The model DLL architecture
Post-Improvement Maintenance Standards
Temporary Exclusion of Sections from Study
Improved Configuration - Accident Classes
Improved Configuration - Speed Flow Types
Improved Configuration - Traffic Flow Patterns
Improvement Standard Effects
Sensitivity Analysis has been introduced to Project Analysis to allow a user to investigate the impact of variations in key parameters on the analysis results. A user can define any number of sensitivity scenarios in which any of the 18 key parameters can be varied. The 18 key parameters cover unit costs, vehicle use, traffic levels and growth, and net benefits. One or more key parameters are varied by defining a multiplication factor and the effects on the outcome an the analysis will be determined. A user determines which variables to vary and this judgment will depend upon the kind of investigation being conducted. Typically the key parameters will be varied to reflect the potential range of forecasts for the parameters.
HDM-4 version 2.0 allows the user to specify an unlimited number of budget scenarios. Each budget scenario defines the road agency financial resources available over the analysis period. The optimised work programme will be produced for each of the selected budget scenarios therefore allowing the user to compare the effects of different funding levels on the network being analysed.
Multi-Criteria analysis (MCA) in HDM-4 project analysis provides a means of comparing projects using criteria that cannot easily be assigned an economic cost.
MCA is supported for a Project Analysis and supports 10 criteria to evaluate:
. Economic ( RAC , RUC, and NPV)
. Safety (Accident analysis)
. Functional (Comfort and Delay)
. Environment (Air Pollution)
. Energy (Energy efficiency)
. Social (Social Benefits)
MCA in HDM-4 is performed using an implementation of the Analytical Hierarchy Process ( AHP ) (Saaty 1980).
It has often been necessary to include the social benefits of road investments within HDM-4. The simple framework for including social benefits has now been made more transparent by incorporating them within the exogenous costs and benefits user interface.
A road network is a considerable resource that has a significant asset value. It is therefore important to effectively manage this asset and to be able to estimate the financial and economic value of road assets as a function of the level of investment. This optional component of HDM-4 Version 2.0 allows a user to estimate the asset value of a network being analysed during the time period of the analysis.
The run-data produced by HDM-4 during an analysis is now output to a single file in Microsoft Access format. The main benefit of this change is that the use of the Access format makes it easier for end-users to access the run-data with widely available software products (such as Microsoft Access, and Microsoft Excel) and easier to share with others users.
For the purposes of users who wish to view the run-data but do not a HDM-4 licence, a free tool, HDM-4 Version 2.0 Report Viewer, will be available.
The import/export data produced by HDM-4 is now stored in a single file in Microsoft Access format, and replaces the multiple *.dbf/*.hdbf files of HDM-4 Version 1.x. The main benefit of this change is that the use of the Access format makes it easier for end-users to access the data with widely available software products, and easier to share with others users.
An import wizard has been introduced that guides a user through the process of importing externally-defined data into HDM-4 version 2.0.
Previously no validation of the imported data was preformed and values that were outside the allowable range could produce numerical errors when an analysis was subsequently performed. HDM-4 version 2.0 introduces the optional validation of vehicle fleet and road network data for incorrect values as the data is being imported.
HDM-4 uses an object-orientated database to store its local data. HDM-4 version 2.0 has been updated to use the latest version of this database to ensure the latest developments and enhancements are available, as well as continued support and backup from the suppliers is accessible.
The definition of new sections has been moved to the work standards folder in the workspace. These new sections are now assigned to alternatives using the new alternatives user-interface. This approach allows new sections to be reused across studies and alternatives.
The management and entry of traffic related data in HDM-4 has undergone a number of changes that effect road networks, sections, vehicle fleets and the three modes of analysis.
The traffic data for a section is now defined for each section within the road network. To enable this to take place a road network is associated with a vehicle fleet. A user can enter multiple years of traffic data which is now defined in terms of absolute vehicle AADTs value.
A traffic growth set defines how the traffic grows over time and is defined within the vehicle fleet and assigned to a section within an analysis. The use interface for traffic growth sets is similar to that used in version 1.x for the definition of normal traffic. As growths sets may be used to define the traffic growth characteristics of multiple studies, the periods are defined as relative years rather than absolute years.
These improvements allow traffic data for a section to be common in each analysis in which the section is included, and for the typical traffic growths to be reused in each analysis. When creating a new analysis a user now only selects the road network to be used, as the vehicle fleet is associated with it. The user then selects the sections to be included in the study and assigns traffic growth sets to each section, using the growth sets defined in the road network's associated vehicle fleet.
HDM-4 version 2.0 includes improved management and organisation of the available report templates. A user can now add report categories, or sub-categories within the reports tree-view, and reports can easily be renamed or moved between categories. The reports no longer have to be stored in the same directory, allowing a user to easily separate HDM-4 default reports and 3rd party report templates.
The bituminous RD & WE models in HDM-4 Version 2 have been updated in accordance with the specification provided by PIARC. The changes include improvements to the pothole progression model, updated plastic deformation coefficients, updated standard deviation of rut depth model, improved user-calibration or the RD models, and updated WE models for patching and preparatory work effects.
The unsealed RD & WE models in HDM-4 Version 2 have been updated in accordance with the specification provided by PIARC. The most significant change is the introduction of three different grading types (non-mechanical, light mechanical grading, and heavy mechanical grading), and improved calibration of the unsealed roughness model using section calibration factors and workspace configuration parameters.
The Road User Effects (RUE) model in HDM-4 Version 2 has been updated in accordance with the specification provided by PIARC. The changes include:
Engine speed model has been updated,
Parts modelling updated to use dFUELavg rather than dFUEL,
Constant Service Life model has been changed so it no longer depends upon the percentage of private use, and
Major update to the modelling of vehicle emissions.
The definition of the triggering logic of work items and improvements has been simplified and improved by the introduction of an improved intervention editor. The main areas of improvement are:
The need to select scheduled or responsive intervention mode for a work item has been removed
The predefined limit parameters associated with the triggering logic are now optionally entered in the intervention editor as part of the main trigger expression.
The triggering of works has been extended to allow the combination of AND /OR logic operators.
Works can now be scheduled to occur in set years rather than just periodically.
The user is no longer constrained to select a trigger attribute from a pre-defined list. The recommended triggers for a particular work item may be ignored (in fact any trigger can be used with any work type).
The user interface in Version 1.x was reported by many users to be cumbersome with many features hidden behind several levels of screens / dialogs with a multiplicity of confusing buttons. To address these concerns the user interface for the definition of analysis alternatives has been redesigned to reduce the number of dialogs and buttons involved, to improve navigation through the alternatives in a familiar style, and to give improved view to the user. The new user interface allows the user to navigate through the alternatives and its assignments using a view similar to the windows explorer directory navigation tree, and uses a context sensitive spreadsheet-type view that facilitates the assignment of maintenance and improvement standards from one dialog.
The model architecture has undergone some revision to improve maintainability, flexibility, and to allow future customisation. Some parts of the analysis framework have been revised to take advantage of these architectural improvements. To the general users these changes will not be visible.
It is now possible to assign a maintenance standard to be applied after a road improvement standard has been applied (i.e. the maintenance standard will only be applied if the associated improvement is triggered). This facility is implemented in the new alternatives user-interface.
When setting up a project analysis it is now possible to select a section for the study, assign the traffic growth set and define its alternatives, but then exclude it from analysis without loss of data (traffic, alternatives, etc.). This was identified by users to be a useful function if several sections have been selected in a project analysis and there is the need to focus on defining and refining the assignments of one section at a time without the overhead of analyzing all the other sections each time.
Calibration Sets have been introduced to allow users to define sets of section calibration coefficients (a calibration item ) for the range of pavement types commonly found on their road network. Sections which have the same characteristics can all use the same calibration . The process of defining a section has therefore been simplified as a user now has only has to select an appropriate calibration item for the section's known characteristics rather than supply values for all the calibration parameters.
Calibration sets are stored under the Configuration folder in the workspace view. When a new road network is created a calibration set for that network is selected, and all sections within the network must be assigned a calibration item defined in that calibration set. To facilitate the new concept of calibration items as section's attributes have been reorganized.
A new HDM-4 data type has been provided to allow the user to model accident effects separately from speed flow types.
An explanatory graph has been added to the user interface to explain the relationship between the capacity characteristic parameters. To reflect the correlation between road type, and capacity characteristics, and to improve consistency, the Number of Lanes ( NLANES ) parameter has been moved to the Speed Flow Type item from the road section.
A graph is now shown on this dialog to reflect the flow distribution data entered by the user. As the user changes this data, the graph changes accordingly. The graph is intended to improve user feedback, and to engender understanding of the effects to the flow distribution data.
After-work attributes for some improvement effects can now be defined either in terms of the change in attribute value or in terms of the final value of the attribute (i.e. either in relative or absolute terms). This is intended to make improvement standards less section specific, so that they can be applied to a group of sections.