The transport sector in Vietnam is a significant and growing contributor to greenhouse gas (GHG) emissions, accounting for 17.80% of the country’s energy-related CO2 emissions in 2014. Da Nang, a key urban center, exemplifies these challenges with high motorcycle ownership, increasing private car usage, and minimal public transport uptake. This study aims to analyze transport decarbonization in Da Nang, offering insights applicable to other Vietnamese cities. Utilizing a GHG emissions simulation, we evaluated the impact of various strategies aligned with the ASI (Avoid-Shift-Improve) framework. The “Avoid” strategy targets travel demand reduction, “Shift” promotes lower-carbon transport modes, and “Improve” enhances vehicle efficiency through technology. We examined four scenarios from 2014 to 2050: Business-As-Usual, a mitigation scenario without international support, a mitigation scenario with international support, and a net-zero transport scenario. Results indicate that early intervention in medium-sized cities can lead to significant emissions reductions and sustainable growth. The findings highlight the importance of public transport infrastructure, technology-driven efficiency improvements, and international cooperation in achieving Vietnam’s net-zero GHG emissions target by 2050. This research informs policymakers on effective strategies for transport decarbonization and supports formulating robust, sustainable transport policies. Particularly, this study shows that targeted transport investments in Da Nang can reduce emissions significantly, with Scenario 3 achieving up to a 50% reduction by 2050 compared to BAU. These results underscore the potential for carbon neutrality through strategic interventions.