Commuter safety continues to be one of the major problems in road transportation especially in urban cities of developing countries. Although road maintenance investments have been established to maintain and improve the quality of roads, only limited studies of its assessment towards commuter safety under the sustainability framework have been conducted. Because the pillars of sustainability – namely economy, environment and society – need to be concurrently considered in the assessment, a systems dynamics approach is used. This is used to develop the relationship of sustainable transportation pillars that are relevant to the current transportation system in Metro Cebu relative to incidences of road fatalities. A causal loop diagram is initially made to identify the key components and their interrelationships as basis in developing a stock-and-flow diagram of the model. The simulation was run from 2024 to 2040, and the results show an increase of road maintenance budget by about 10% yielded a practically higher and more stable road maintenance-to-decreased fatality ratio starting 2032. Although increasing the budget yields a more stabilized ratio, its trend is slower. These results can help policymakers develop better strategies to improve safety without much compromise to other aspects of a sustainable transportation system.