Waste or additional costs in infrastructure projects such as jetty projects are often caused by rework. Besides having an impact on costs, rework is also a very significant contributor to waste or adding time which causes delays in the completion schedule of the project. A lot of research on rework has been carried out on both building and road construction projects, but there is no jetty construction project. This study aims to develop improvement scenarios to minimize the emergence of rework on pier infrastructure projects by modelling and simulating cost performance. The research variables were obtained based on the results of a literature study by asking for opinions from experts who are compatible in their scope. The initial model used the causal loop diagram form which was later developed into a Stock Flow Diagram, after which a repair simulation was carried out using the dynamic system method to determine the effect on cost performance. From the research results obtained 14 factors that affect the cost and time performance on the jetty project, the implementation of a dynamic system can provide the optimum solution with the ability to reduce the percentage of the number of reworks by 24.12% for 12 months.

The paper investigates Bayesian approach to estimate generalized true random-effects models (GTRE). The analysis shows that under suitably defined priors for transient and persistent inefficiency terms the posterior characteristics of such models are well approximated using simple Gibbs sampling. No model re-parameterization is required. The proposed modification not only allows us to make more reasonable (less informative) assumptions as regards prior transient and persistent inefficiency distribution but also appears to be more reliable in handling especially noisy datasets. Empirical application furthers the research into stochastic frontier analysis using GTRE models by examining the relationship between inefficiency terms in GTRE, true random-effects, generalized stochastic frontier and a standard stochastic frontier model.

Strengthening the functioning of existing rural piped water supply systems is a critical strategy for ensuring household water security, particularly in water-scarce contexts. Improving operation and maintenance (O&M) of the systems is an important area of focus, commonly plagued by poor reliability and functionality over time. From an economic perspective, there is an opportunity to optimise O&M input efficiencies as a foundation for improved management. This paper presented challenges and opportunities to optimise O&M input efficiencies based on an analysis of water supply systems in Vietnam’s highland areas characterised by mountainous terrain and water scarcity. The analysis focused on state-based agencies for O&M given their mandate for restoring the inefficient systems and identified input norms for guidance on how to optimise O&M activities. We applied an input-oriented data envelopment analysis (DEA) model under constant returns to scale assumption to estimate technical, economic and allocative efficiencies. The results identified efficiency levels of 90%, 30% and 33% respectively. The study suggests a 10% reduction in general input amounts and identified efficient input target values reveal potential reduction rates for technical labour (12%), electricity (12%), as well as the technical and economic norms of technical labour (0.86 person- day∙(100 m³)^–1 water sold) and electricity (0.53 kWh∙m^–3 water sold). The policy implications for O&M state-based agencies include the adoption of input-based contracting mechanisms, while the government is encouraged to approve water tariffs and provide compensation based on input items to promote water service supply as a public good in water- scarce and challenging areas.