<p>Probabilistic condition and safety maintenance strategies on concrete highway bridges with chloride-based deterioration are cost-prioritized, using a self-developed Monte Carlo platform. Practical probabilistic data of four maintenance types are gathered; Silane treatment (SL), Cathodic protection (CP), Minor concrete repair (CR), and Rebuild (RB). Six combined maintenance strategies (2–3 maintenance types) are proposed. From the study, the combined strategy of SL + RB is found cost-optimum based on 50-year present value of expected cumulative cost, nevertheless there is 55% probability of requiring CR for preventing severe condition deterioration. This severe condition deterioration probably leads to severe safety deterioration which in turn requires high-cost RB. Moreover, the optimal first application time of low-cost SL is found equal to its lower limit to avoid high-cost maintenance types, but its optimal subsequent application time is extended to reduce cumulative maintenance cost. For the other optimized strategies, the interaction between maintenance types basically leads to the avoidance of high-cost maintenance types for reducing cumulative maintenance cost. Using the optimal data for secondary analysis, 99-percentile maintenance cost and CO₂ emission from maintenance (including its sensitivity analysis) are discussed as further development from the previous study. Apparently, the strategy of SL + CR is found CO₂-minimum, while there is 28% probability of requiring RB for preventing severe safety deterioration. Moreover, the expected cumulative CO₂ emission is insensitive to low-emission maintenance by SL, while sensitive to high-emission maintenance by CP, CR, and RB. The intensity of sensitiveness depends on maintenance strategies. Finally, the limitations of the study are discussed for further study.</p>