Subway operators introduced linear metros in 1990s and continued successful urban passenger transport service in many large and dense cities in Japan for more than a quarter century. A significant disadvantage of the linear metros is the relatively low energy efficiency. Therefore, Japan Subway Association (JSA) started a technical challenge to reduce the traction energy consumption of linear metros in 2012. After engineering efforts for three years, the improved automatic train operation (ATO) achieved the energy-saving of more than 16%. This paper technically explains the idea and the concrete methods in the successful technical challenge.