Road networks are essential to the functioning of modern society. The levels of service they provide strongly affect the distribution of resources and goods, the accessibility and economic development of regions and the mobility of citizens. Since roads, including all of the objects of which they are composed (e.g. pavement, bridges, and tunnels) deteriorate over time due to environmental factors and use, and the required levels of service, in general, either increase or remain constant, the road sections must be maintained by executing interventions (e.g. asphalt crack sealing and chip sealing of pavement, painting or replacing the girders of a steel bridge).
There are an extensive number of possible intervention strategies (e.g. the types of interventions to be executed and the time of execution) that road agencies may use to ensure that roads continue to provide an adequate level of service. The decision of the intervention strategy to be followed is often based solely on road agency costs, i.e. it is determined to be the one that results in the lowest agency costs. An illustrative example of the agency costs of two possible intervention strategies is shown in Figure 1, where the first strategy consists of more frequent less expensive interventions and the second strategy consists of less frequent more expensive interventions.
Figure 1. Two example intervention strategies
Road agency costs, of course, are not the only costs that need to be taken into consideration when determining optimal strategies. Almost every intervention on a road affects the amount with which society benefits from the transportation network to which the road belongs. Normally, benefits decrease during the intervention and increase between interventions. For example, during the intervention there may be an increase in travel time costs due to the traffic jams resulting from closing two lanes on a four-lane highway, or an increase in noise to those living next to the road section, or an increase in emissions that may negatively impact the climate or the health of persons in the immediate vicinity of the road section. Between interventions there may be lower routine maintenance costs and a decrease in vehicle operating costs. The impact of interventions on all of the benefits, both during and between interventions, should be taken into consideration when determining optimal intervention strategies to ensure the maximal societal benefit from the transportation network.
Since the consideration of all of the road benefits in the determination of optimal intervention strategies requires the valuation of many benefits that are not naturally in monetary units (e.g. noise costs, CO2 emission costs, and accident costs), the value of these units depends greatly on the utility functions of the affected individuals and organisations (or stakeholders). It is expected that the variations in these values, especially in the cases of conflicting values, have a significant effect on the optimality of intervention strategies, and that there variations are significant between road types (e.g. motorways, rural roads) and between stakeholders. As public-oriented network managers road agencies need to know the varying and conflicting valuation of stakeholders’ requirements and expectations and consider them when deciding on the optimal intervention strategies. Central questions in this regard are:
- Who are the stakeholders of a particular road network?
- What are the benefits and expectations of the road network for these stakeholders?
- How does the valuation of these benefits vary?
- Which intervention strategies are optimal for the likely values of these benefits?
- How can optimal intervention strategies be selected taking into consideration the variation in of these values, especially in the case of conflicting values?
Research Objectives and Results
The research project “Stakeholder benefits and road intervention strategies (SABARIS)” contributes to the objective A) “Meeting stakeholders’ requirements and expectations” of the ENR2 research programme. It addresses the challenge of road agencies of selecting an intervention strategy for a particular part of a road network that is optimal taking into consideration the varying and sometimes conflicting values of road benefits for the stakeholders of this road section.
The objective of the project SABARIS is to support this decision making at road agencies and provide answers to the aforementioned questions by:
- identifying the stakeholders of different types of roads in different European countries,
- determining the road benefits and expectations for the stakeholders,
- determining ways of engaging the stakeholders in benefit determination and in the communication to them that their concerns are being considered and managed,
- analyzing the values of the road benefits for the stakeholders,
- assessing the impact of the valuation of benefits on the optimality of intervention strategies for roads, and
- evaluating the optimality of the intervention strategies due to variations in and conflicts of the benefit values.
The project SABARIS will deliver a number of results:
- classification of stakeholders in terms of road types and road benefits,
- ranking of benefits for different categories of road types according to stakeholder valuation,
- stakeholder engagement strategies for different categories of road types,
- a prototype optimization tool for the evaluation of intervention strategies that simultaneously takes into consideration the different valuations of road benefits from multiple stakeholders,
- guidelines for use and implementation of such an optimization tool, in general and for different road types, and for different road agencies, and
- case studies illustrating and comparing the implementation, usage and outcome of the optimization tool.
It is planned that the optimization tool for the evaluation of intervention strategies is applicable to all road types within the European road network and facilitates the decision making on the network level. However, it is also intended to identify typical clusters of roads (e.g. roads exhibiting similar characteristics such as a certain range of average daily traffic) based on their associated benefit types and propose optimal intervention strategies for these clusters.
Although the determination of optimal intervention strategies has been studied extensively by others, the total benefits related to a road network and their effect on the optimality of interventions has not been investigated. Moreover, the differences and possible variations in the valuations of the benefits that are not naturally in monetary units have not been included. The innovativeness of this research project lies in the optimization of intervention strategies taking into consideration the varying valuation of the individual and overall benefits for multiple stakeholders of road networks.
In this section the main steps of the project are explained as well as the principal tasks and methods of data collection involved for each. Furthermore, the relation of each research step to the international state of the art is outlined.
The research tasks are:
- stakeholder identification,
- analysis of road benefits and stakeholder engagement,
- valuation of road benefits,
- optimization of intervention strategies,
- case studies, and
- sensitivity analysis for variations of the value of benefits.
The goal of this task is to identify and classify stakeholders of road networks that affect and are affected by maintenance interventions and need to be managed when implementing the interventions.
Stakeholder analysis is a common management tool to understand the interest and relevance of individuals, groups and organizations for an action, project or policy. Stakeholders are any individual, group or organization who can affect or is affected by the achievement of the objective of the action, project or policy (Freeman, 1984). Although stakeholder analysis has been applied for construction projects (e.g. Newcombe, 2003; Olander, 2007), a systematic analysis of stakeholders that affect and are affected by maintenance interventions is still missing. There is an ongoing action of the PIARC committee D1 on “Road Infrastructure Management” which includes a first attempt to group road stakeholders.
Based on the PIARC action, a thorough literature review and a number of interviews/workshops with experts from road agencies in different countries, individuals, groups or organizations that have a stake in road maintenance are identified. These stakeholders will be clustered around typical road networks (combinations of road types and regional areas).
Analysis of road benefits and stakeholder engagement
The goal of this task is to identify road benefits and engagement strategies for the identified stakeholders of road networks.
A number of researchers and organizations have structured benefits and assembled models from which to approximate them to provide guidance of how to evaluate infrastructure projects. For example Land Transport New Zealand (LTNZ, 2006) structure benefits as 1) travel time benefits, 2) vehicle operating benefits, 3) accident benefits, 4) comfort benefits, 5) productivity benefits, 6) driver frustration benefits, and 7) emissions benefits. However, a structured and comprehensive overview of different stakeholders (e.g. road user, road owners, local residents, taxpayers, political bodies) and the associated benefits and expectations has not been provided. Moreover, the way of engaging road stakeholders in the evaluation of their benefits and the communication to them that their concerns are being taken into consideration (e.g. passively inform, dialogue) has not been examined.
Based on a comprehensive literature study, a number of expert interviews, and selected interviews with stakeholders, an overview of total road benefits and engagement strategies will be created. In addition an appropriate benefit structure (e.g. complete, operational, decomposable and non-redundant) will be developed to serve as a basis for the evaluation of the benefits on road networks, as well as the impact of the valuation of each benefit type on the optimality of intervention strategies. The benefit structure will relate the road benefits and the engagement strategies to the different stakeholders indentified.
Valuation of road benefits
The goal of this task is to estimate the values of each of the benefits and their variation for stakeholders of road networks.
One way of taking benefits into consideration that are not naturally in monetary units is to monetarise them. This can be done in different ways, which are well known and include various willingness to pay methods such as opportunity cost methods, the direct estimation of demand curves, indirect market methods, market analogy method, the trade-off method, intermediate good method, asset valuation method, hedonic pricing method, travel cost method, defensive expenditure method, contingent valuation methods, and shadow pricing methods. Multiple researchers have investigated the effectiveness of these methods in evaluating diverse benefits, but they have not been applied for the valuation of road benefits.
The literature from other fields will be reviewed and the best methods for the evaluation of each road benefit will be selected. At least two methods will be used to estimate the values of each of the benefits for different stakeholders, in order to eliminate errors that might be produced from using only a single method, as demonstrated by Ihs (2004) in the evaluation of road comfort costs. Range and distribution of the values for each of the benefit types are also determined.
Optimization of intervention decisions
The goal of this task is to develop an optimization tool for the evaluation of intervention strategies taking into consideration the different valuation of road benefits from stakeholders.
Many models have been developed for the evaluation of intervention strategies, including Ferreira et al. (2002), Yoo et al. (2008) and Abaza et al. (2009). These models vary in the level of detail used in the definition of interventions and the description of the road sections, and in the types and level of detail of the costs and benefits that are considered. Of particular interest are those models used in state-of-the-art road management systems. For example, the road management system that is developed by the World Bank, the Highway Development and Management Tool, uses a holistic approach to road management and provides a unified framework for decision making at the strategic, programme and project level of application.
It is intended to study and compare the existing models used in state-of-the art road management systems (e.g. pavement management systems) at road agencies to determine optimal projects and strategies. The aim is to find those model elements that can be used and further developed to consider the variation of the value of road benefits in the evaluation of intervention strategies. A new model will be built using the most suitable existing model elements and implemented in a straightforward prototype software tool (e.g. Excel® spreadsheet) that will allow the quick determination of the optimal intervention strategies for a selected road network. The model will be tested and detailed through some simulations on a Virtual Road Network®.
The goal of this task is to illustrate and compare the use of the developed optimization tool for particular parts of the European road network.
At least two different road networks will be chosen as case studies to illustrate the functioning of the optimization tool, and to show how the tool could be implemented within the asset management processes of a road agency. The case studies will be used to compare the selected roads and networks with regards to the effect of network peculiarities on the optimal intervention strategy and to investigate the effect of organization peculiarities on the implementation of the optimization tool.
The goal of this task is to evaluate the sensitivity of the optimal intervention strategies determined in the case studies to fluctuations and conflicts in the values of the road benefits.
As previous research has shown to some extent there is always uncertainty inherent in the values of benefits (Salem, 1999; Li and Sinha, 2004). Most benefits of maintenance interventions cannot therefore adequately be approximated deterministically. They vary significantly due to the variation in number and type of stakeholders, and due to the valuation of benefits within and between stakeholder groups. A comprehensive analysis of the sensitivity of intervention strategies to varying and conflicting benefit values has yet to be done.
Based on the results of the valuation of benefits and the optimization of intervention strategies the effect of different distributions of benefit values on the optimality of intervention strategies will be examined. The sensitivity analysis will be conducted for single benefits and combinations of benefits that correspond to typical stakeholder groups, and road types.
- Abaza, K.A., Ashur, S.A., 2009, Optimum microscopic pavement management model using constrained integer linear programming, The International Journal of Pavement Engineering, Volume 10, Issue 3, pages 149-160.
- Ferreira, A., Picardo-Santos, L., Antunes, A., 2002, A Segment-linked Optimization Model for Deterministic Pavement Management Systems, The International Journal of Pavement Engineering, Vol.3, (2) , pp.95-105.
- Freeman, R. E. 1984. Strategic management: A stakeholder approach. Boston: Pitman.
- Ihs, A., 2004, The influence of Road Surface Condition on Traffic Safety and Ride Comfort, Queensland, Australia: 6th International Conference on Managing Pavements, October.
- Li, Zh. and Sinha, K.C., 2004, Methodology for Multicriteria Decision Making in Highway Asset Management, Transportation Research Record, Vol.1885, 79-87.
- LTNZ, 2006, Economic Evaluation Manual Vol.1, Land Transport New Zealand, New Zealand.
- Newcombe, R., 2003, Construction Management and Economics, 21, 841–848.
- Olander, St., 2007, Construction Management and Economics, 25, 277-287.
- Salem, O.M., 1999, Infrastructure Construction and Rehabilitation: Risk-Based Life Cycle Cost Analysis. PhD Thesis, University of Alberta, Canada.
- Yoo, J., Garcia-Diaz, A., 2008, Cost-effective selection and multi-period scheduling of pavement maintenance and rehabilitation strategies, Engineering Optimization, Volume 40, Issue 3, March, pp. 205-222.