The mission of any metro transportation undertaking is to provide safe, reliable, efficient, high quality service to its passengers in a cost effective fashion. To meet this business need, our metro systems are increasingly being automated. Any new metro system constructed today would almost certainly incorporate some level of automation with many modern metro systems now providing driverless or unattended train operation. In addition, higher levels of automation are also being introduced into the older metro systems around the world in response to demands for increased capacity on the existing infrastructure, enhanced levels of safety, improved customer service, and reduced operating costs. This article examines the benefits of automation, the various levels of automation that can be deployed, the maturity of the technology, and the challenges of selecting the appropriate level of automation for a specific application. The article focuses on automation of metro systems. Automation of our intercity main lines, high speed railways, and freight lines will be addressed in a separate article.