The real-time city is now real! The increasing deployment of sensors and hand-held electronics in recent years is allowing a new approach to the study of the built environment. The way we describe and understand cities is being radically transformed - alongside the tools we use to design them and impact on their physical structure.

Scholars back in 1995 speculated about the impact of the ongoing digital revolution on the viability of cities. Only 14 years ago, the main- stream view was that, as digital media and the internet had killed distance, they would also kill cities. Technology writer George Gilder proclaimed that “cities are leftover baggage from the industrial era” and concluded that “we are headed for the death of cities”, due to the continued growth of personal computing, telecommunications and distributed production. In fact, cities have never prospered as much as they have over the past couple of decades. China is currently building more urban fabric than has ever been built by humanity. And a particularly noteworthy moment occurred last year: for the first time in history more than half the world’s population – 3.3 billion people – lived in urban areas. The digital revolution did not end up killing our cities, but neither did it leave them unaffected. A layer of networked digital elements has blanketed our environment, blending bits and atoms together in a seamless way. Sensors, cameras and microcontrollers are used ever more extensively to manage city infrastructure, optimise transportation, monitor the environment and run security applications. Advances in microelectronics now make it possible to spread “smart dust” networks of tiny, wireless, micro-electromechanical system (MEMS) sensors, robots or devices. Most noticeable is the explosion in mobile-phone use around the globe. More than four billion mobile phones were in use worldwide by early 2009. Across socioeconomic classes and five continents, mobile phones are ubiquitous: they allow us not only to communicate with each other in unprecedented ways, but to create a pervasive sensing network that covers the whole globe. One consequence of this process is particularly important: cities can start to work as real-time control systems, and this opens up a new world of opportunities...