In the past decades, the expansion of metro systems worldwide played an important role in connecting the metropolitan areas. In 2014, there were 157 cities around the world that operated metro networks. In terms of ridership, infrastructure and highest number of cities with metro systems, the Asia-Pacific region was at the forefront.
As travel and transportation are proliferating in response to passengers’ demands and technological progress, the tendency of rail automation is gaining a lot of attention. In metro systems, the concept of automation refers to the interchange of responsibilities between the train driver and the train control system. Whether the transfer is only made regarding basic tasks, like preventing collisions or automatic braking (Automatic Train Protection), or to a more extensive degree, in which setting the train in motion or stopping the train is done using an Automatic Train Operation in the presence of a train driver or train attendant, the fundamental characteristic of automated metro lines is achieved at the highest state of automation - in the absence of the train driver - also known as Unattended Train Operation (UTO).
As of February 2017, 81 percent of driverless metro lines were located in cities with over 500,000 inhabitants. As the automation is exponentially growing, the recent forecasts estimate the total length of automated metro lines to exceed 2,200 km by 2025, with the MENA and Asia regions being the leading forces in this expansion.