The Clean Development Mechanism (CDM) aims to help developing countries cut down on greenhouse gas emissions in the transportation sector. However, the program has mainly focused on big projects and hasn't done much for sustainable development. Fuel and mode switch projects are popular in the CDM, but they might not be enough to make a real difference. A different approach called Nationally Appropriate Mitigation Actions (NAMAs) could work better for transportation policies. So far, no transportation projects have been approved under this new approach. The CDM needs some changes to really help reduce emissions in the transportation sector.