Traffic impact assessment (TIA) is a powerful tool for engineers and planners to determine the possible effects of a project on the transportation and traffic system. Often it is applied only to the direct impact area and countermeasures for potential negative impacts are specific for the development. This paper presents TIA as a useful tool for local governments, especially for managing traffic and in planning their respective transportation systems. Two cases involving projects that were required to undertake TIA are compared, and results are examined in relation to the sustainability of traffic management and transportation planning strategies in Metro Manila and in other cities as well. The experiences presented and discussed in this paper underline the need for the government to take an active role in promoting TIA. This will ensure that stakeholders would participate in the TIA process, leading to the careful and substantive assessment of impacts of proposed developments.