Objective: Static long-term decision-making processes for road assets adaptation on the dynamic effects of climate change seem to be ineffective because the proposed proactive measures might not address the actual climate at the fixed date the decision-maker imposes them to be implemented but by giving a time range of expected implementation in the future by following the actual evolvement of climate seems to be much more beneficial. This research recognizes that a methodology for dynamic planning is needed and a study of the climate variables that are correlated with and affect the road tunnel systems in the Netherlands is carried out. Research's main goal is to develop a structured methodology for long-term road tunnel adaptation on the effects of climate change in a dynamic rather than a static way, proposing multiple adaptation actions of increasing robustness and time range of expected implementation in the future, avoiding fixed date ones. Method: The Dynamic Adaptive Policy Pathways (DAPP) approach was chosen because it is the model that realizes dynamic long-term decision-making by proposing strategic pathways of actions. This research investigated the 6 out of 10 DAPP steps and executed them through known methods and tools in three phases. Firstly, the identification and analysis of the climate variables that were correlated to road tunnels are conducted. Phase I started with the Function Breakdown Structure analysis of a road tunnel system defining functional requirements, the Hamburger model for functional decomposition, and Fault Tree Analysis for function failure modes identification was conducting. Additionally, quantification of the failures in unavailability rate terms and qualitative analysis of the corresponding impact on six organization values were executed. Then, in Phase II, the definition of adaptation measures for road tunnel unavailability prevention and consequences mitigation was carrying out and visualized through BowTie analysis diagrams. Finally, in Phase III, the modeling of the adaptation strategy for cause prevention and impact mitigation was presented in DAPP maps. Result: The ongoing climate change in the Netherlands showed that changes in several climate variables affect some primary road tunnel infrastructure functions in an analysis until 2100. By implementing DAPP, I was able to define and conclude to simpler and more compact decision-making plans dealing with deep uncertainty over longer timeframes. These adaptation plans for cause prevention and impact mitigation can be applied regardless the actual climate conditions. In the DAPP methodology, the actual climate conditions indicate the moment the proposed adaptation actions are taken and consequently time flexibility is achieved. The research results seem more effective than the ones of the currently applied decision-making practices. The added value of the DAPP approach lies in its flexible character compared to the to date practices, which mainly define robust adaptation actions that deal with any extreme future and propose strict implementation times. With DAPP, a decision-maker can propose actions of different robustness, that can tackle the same issue by allowing him to select the desired robustness considering the implementation timeframe. As far as the impact mitigation is concerned, the DAPP approach helps a decision-maker to define multiple mitigation actions, which deal with the same function impact and to select the most appropriate. This selection depends on the scoring of the mitigation actions regarding their individual contribution on impact mitigation. Therefore, a useful decision-making methodology for long-term road tunnel assets adaptation, led by environmental changes, was established.