Abstract

Maintenance flexibility has been promoted as a value driver for long-term public–private partnerships (PPPs). However, the value and risk associated with this value driver have not been properly quantified in the Value for Money (VfM) assessment literature. To bridge the gap, a novel stochastic modelling methodology is proposed to characterize the complex interactions among the lifecycle cost (LCC), performance deterioration and maintenance strategies. Four different maintenance strategies are designed to emulate the practice in the traditional and PPP delivery methods. The LCC includes the direct maintenance cost, user cost, residual value, and payment deduction, the last three often being neglected in VfM assessments. Simulation-based optimization and dynamic programming analysis are used to determine the probability distributions of the LCC and the VfM. A hypothetical highway PPP project under an availability payment model is selected as a case study. The results show that maintenance flexibility is indeed able to reduce the LCC for the private party. However, this private efficiency, if not properly regulated, could cause a reduced asset residual value and an increased user cost, making the public party worse off. In addition, for all potential maintenance strategies, the public sector is found to retain significant lifecycle cost risk, largely in the form of user cost.

摘要

维护灵活性已被提升为长期公私伙伴关系（PPP）的价值驱动力。但是，与此价值驱动因素相关的价值和风险在“物有所值”（VfM）评估文献中并未得到正确量化。为了弥合差距，提出了一种新颖的随机建模方法来表征生命周期成本（LCC），性能下降和维护策略之间的复杂相互作用。设计了四种不同的维护策略来模仿传统和PPP交付方法中的实践。LCC包括直接维护成本，用户成本，残值和付款扣除，后三项通常在VfM评估中被忽略。基于仿真的优化和动态规划分析用于确定LCC和VfM的概率分布。选择了在可用性支付模式下的假设公路PPP项目作为案例研究。结果表明，维护灵活性确实能够减少私人方的LCC。但是，这种私人效率，如果得不到适当的监管，可能会导致资产残值减少和用户成本增加，从而使公共部门的状况更糟。此外，对于所有潜在的维护策略，公共部门被发现保留了很大的生命周期成本风险，主要是以用户成本的形式。结果表明，维护灵活性确实能够减少私人方的LCC。但是，这种私人效率，如果得不到适当的监管，可能会导致资产残值减少和用户成本增加，从而使公共部门的状况更糟。此外，对于所有潜在的维护策略，公共部门被发现保留了很大的生命周期成本风险，主要是以用户成本的形式。结果表明，维护灵活性确实能够减少私人方的LCC。但是，这种私人效率，如果得不到适当的监管，可能会导致资产残值减少和用户成本增加，从而使公共部门的状况更糟。此外，对于所有潜在的维护策略，公共部门被发现保留了很大的生命周期成本风险，主要是以用户成本的形式。