410 ITU‐T's Technical Reports and Specifications 3.3 Lifecycle and obsolescence 3.3.1 Life of built infrastructures and provision for replacement The built infrastructure may be considered to have a life ranging from 5‐100 years. A common infrastructure therefore needs to be accessible to allow service providers to carry out work including new service provision, upgrade and replacement. Examples of typical life times are: ICT (5 years), rail track and signalling (15‐20 years, [b‐8]), road surface (20 years, [b‐8]), electricity (20 years), data centre 20 years [b‐8], storm water run‐off (30 years), water pipeline (100 years [b‐8]), and sewerage (100 years [b‐8]). 3.3.2 The built‐infrastructure – radical changes can be envisaged Infrastructure, such as a utility tunnel, could have a lifetime of 100 years or more. The speed of technological advances especially in the ICT sector could render some of the city infrastructure obsolete within 10 years. Examples include: self‐drive vehicles, tracked buses superseding rail, delivery services by autonomous vehicles including drones, solid refuse collection using underground ducting powered by suction of air. An issue for planners to consider is to what extent the infrastructure should be future‐proofed. Provision for additional storm water run‐off is a major consideration for some cities as the impact of climate change is factored in. One example is G‐Cans Project, or the Metropolitan Area Outer Underground Discharge Channel, which is the world's largest underground flood water diversion facility. It is located between Showa in Tokyo and Kasukabe in Saitama prefecture, on the outskirts of the city of Tokyo in the Greater Tokyo Area, Japan [b‐13]. Utility tunnels may be an essential part of a SSC's storm water run‐off plan. 3.3.3 Powering the sensor layer network Powering the sensor layer network is an important lifecycle consideration. Visiting remote locations to replace batteries in wireless sensors is an expensive service maintenance consideration. A battery life of less than 10 years can destroy a remote sensor business proposition. Wireline options should therefore be considered as an alternative to wireless devices. Box 1 Example: Power over Ethernet [b‐14] can power sensors or actuators in a sensor layer network without recourse to batteries or a separate electricity supply from the network connection. Box 2 Example: The HomePlug Powerline Alliance (HPPA) has developed standards and technology enabling devices to communicate with each other, and the Internet, over existing home electrical wiring. Power and communications may therefore be combined over a common mains facility to sensors or actuators on the periphery.