Sustainable efficiency indicator for urban transportation: Case study of public bus and rapid transit systems in Bangkok

Bangkok, the capital of Thailand, is confronting critical traffic congestion caused by the large number of private vehicles. In 2019, the city was ranked eleventh highest on the global traffic index. Public transport was proposed as the key to alleviating the problem. Nonetheless, the sustainability of public transportation should be evaluated from environmental, economic, and social perspectives to support policy decision-makers and monitor the improvement. This research developed a sustainability indicator and used a case study to assess the sustainability of public transportation in Bangkok, by comparing the public bus to the rapid transit (electric rail transportation) service due to their high use rates in Bangkok. A sustainable efficiency indicator (SEI) was developed using the concept of eco-efficiency and the negative impacts were extended to cover environmental, economic, and social aspects. The results showed that the environmental impact of the bus was greatest during the operational phase, whereas for rail transport, it was greatest during the construction phase. In terms of the economy, because the railway system had been designed to service a large population, an increase in passenger numbers for rail transportation could increase its sustainable efficiency. The social impact was assessed based on a satisfaction survey for each of the two types of transportation. All the impacts were converted into monetary values to calculate the SEI. The SEI could also be used to monitor the enhancement of sustainability effectiveness as a tracking performance indicator.