Environmental co-benefits of public transportation improvement initiative: the case of Trans-Jogja bus system in Yogyakarta, Indonesia

•We assess the environmental co-benefits of public transport improvement.•We take a case study driven by addressing local non-environmental problem.•Aiming at local non-environmental problem is found to be less effective.•Aiming at local and global environmental benefits produce comprehensive measures.•We provide insights on how to advance the environmental co-benefits.

Many parts of the world have increasingly experienced the impacts of climate change. Data shows that transportation sector is one of the major contributors to greenhouse gas emissions. In line with this issue, more cities in developing countries have taken innovative initiatives to create sustainable urban mobility by, among others, revitalising the role of their public transport systems. However, the objectives vary widely and are often aimed at solving local problems rather than tackling global warming. Meanwhile, studies have suggested the potential of gaining both local and global benefits simultaneously if the policies taken are focused directly on reducing greenhouse gas (GHG) emissions as the intended benefit. This paper attempts to confirm this by looking at the impact of a conventional policy-making process. It estimates the environmental co-benefits potentials of both air quality improvement and CO2 emission reduction generated by an urban public transport improvement project. It takes Trans-Jogja bus system initiative introduced in Yogyakarta Special Region Province, Indonesia, as the case study. This case study is relevant considering that the project was originally aimed at simply improving the city's public transport quality. In other words, the intended benefit was solving local problem whereas GHG emissions reduction was perceived as the co-benefit. Finally, it provides insights regarding the obstacles and opportunities to advance the environmental co-benefits.