Background: This study aims to examine to what extent sustainability has been incorporated into assessments of road infrastructure projects. It identifies promising approaches that include indicators reflecting core sustainability criteria, determines criteria that were insufficiently covered as indicators, and develops an integrated indicator set covering all criteria. Methods: A systematic review was performed to obtain all related papers/reports in two academic databases: Scopus and Web of Sciences. The indicators extracted from papers/reports were first coded, then evaluated by using quantitative and qualitative content analysis. Results: The project appraisal methods for decision-making is found to be a promising approach, covering more extensive criteria than others. Two criterianamely adaptation and precaution and intergenerational equitywere hardly ever adopted as indicators. Ten main groups of indicators were extracted to construct an integrated set incorporating all core criteria. Conclusions: Some criteria appear to have become mainstream, while others deserve attention. The safest choice is to combine methods/tools or to adopt the integrated set developed for exhaustive criteria inclusion.

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In planning regional road development, planners often face a challenge to reconcile various interests and interpretations on the ultimate goals which complicate the discussion decisionmaking processes. This situation is defined as strategic ambiguity. Standard procedures for impact assessment are mostly ineffective at offering solutions that satisfy all involved stakeholders. This paper analyses the situation by using a Multiple Stream Framework (MSF) approach. MSF identifies three factors, labelled "streams', i.e. the problems, the solutions, and the politics streams, that open sustainability 'windows' for integrating different interests. This paper investigates the opening of such windows in two highway projects in Indonesia. Both projects showed a high ambition for achieving environmental sustainability. In these cases, the window was opened through (i) recognition of the problems and the solutions by the active involvement of stakeholders, (ii) coalitions with influential stakeholders for political supports, and (iii) mobilization of resources and policy networks by the stakeholders. It is concluded that planners might influence the streams to outline decision-making processes and to implement environmental impact assessments effectively.

There has been a growing interest in developing tools to assist decision-making in moving towards sustainable development, such as Sustainability Assessment (SA). It is argued here that more advanced and sophisticated tools are less useful than strengthening institutions when it comes to better engagement of stakeholders and more integrated decision-making. This paper aims at understanding barriers that impede the implementation of an SA tool for road project planning by examining how and when practitioners experience these barriers. From the empirical perspective of Indonesian road planning practitioners, the study reveals the five most influential barriers, including i) insufficient funding support, ii) limited skilled personnel that can use the tool, iii) unavailability of data and information, iv) unavailability of a specific arena for decision-making, and v) unavailability of detailed procedures/manuals. This research discusses strategies for successful implementation, particularly in a context that is less favourable to integrated decision-making, such as Indonesia.

Preface"Sustainability" has become a buzzword in both science and policy, and academics and politicians not only use the term often and in many different contexts, but also assign it multiple meanings. The emergent meanings are contradictory, ambiguous, and diverse. There is no straightforward way to grasp what the notion means without examining who interprets it, when, where, and why. This dissertation arose from this observation. As a government employee for more than 11 years, I found that the words "sustainability" and "sustainable development" had started to appear in policy documents, the speeches of senior staff, and politicians' statements. However, it is challenging to translate the abstract notion into a clear public program, policy, and project with specific and coherent expected outcomes. viii WUR, Giovanni Vecchio, a visiting PhD scholar from Politecnico di Milano, introduced me to the topic of urban transportation planning. To Laksmi Darmoyono, I thank her comments on the PhD project proposal and fruitful discussions about road infrastructure development in Indonesia while she was completing her PhD research at the University of Groningen. I am also profoundly grateful for Dr. Myra P. Gunawan and Dr. Hastu Prabatmodjo (Bandung Institute of Technology). They supported and recommended me to pursue a PhD degree.Fifth, I am very thankful to the Department of Human Geography and Spatial Planning (SGPL) members at Utrecht University. I thank Julie Leijtens, the department manager, and Karlijne and Marleen, the department secretaries, to help me with paperwork, research budgeting, and many other administrative things. I also thank Zinan,