The stability and livability of the world's growing urban regions is going to depend more than ever on advances in public-infrastructure engineering, says Brad Allenby.

"The accelerating urbanization of the species is rapidly increasing the complexity of the urban environment for humanity as a whole," he says. "This makes urban-system infrastructure a critical component in maintaining stable, functioning societies and ensuring quality of life."

Allenby, a professor of civil, environmental and sustainable engineering in the Ira A. Fulton School of Engineering at Arizona State University, will elaborate on his ideas in a presentation at the American Association for the Advancement of Science annual meeting in Chicago.

Responding to the challenges emerging from the world's rapid urban population growth will fundamentally change how the engineering of public infrastructure is done in the future, he contends.

Allenby explains that this accelerating growth is driving an increasing reliance on information and communications technology - in everything from "smart buildings" that manage themselves to reduce energy consumption, to transportation networks that monitor themselves to prevent traffic and instruct drivers how to avoid congestion.

The integration of that kind technology into conventional infrastructure systems presents one of the biggest tasks in developing sustainable urban systems.

First, engineers have to deal with managing the complicated interactions between various information and communication systems - even as those systems themselves are evolving in complexity and capabilities.

Information technology is moving toward "autonomic" systems, Allenby says. These are systems capable not only of defining themselves in real time to meet user requirements but also, in the case of a problem, diagnosing and fixing their own internal faults and malfunctions. To do this, such systems are also being engineered with the ability to "learn" new functions.

The very complexity of such technological capabilities "introduces uncertainty in the designed urban environment," Allenby says. "The public policy implications and social ramifications of such technological evolution are yet to be addressed."

What issues arise?
For one, personal privacy becomes ever more difficult in an age where advanced technology greatly expands the possibility of surveillance of individuals.

Cell phone and toll technologies and global-positioning systems can keep track of where you've been, while your credit card and online history provide details about what you're doing.

The gaps between those who can use the plentiful information systems in the modern economy, and those who can't - what Allenby calls the "digital divide" - may be growing larger, with serious implications for employment, and the ability of poorer countries to develop.

As information systems in urban environments begin interacting with each other, Allenby says, their behavior cannot be predicted even by the experts who designed them.

This makes it critical to study how complex systems such as cities can be made more resilient. "We can't predict or identify all the problems and opportunities that may arise," Allenby says, "but we can try to design our cities and their infrastructure so that we're better able to manage them when the problems and opportunities do arise."

Overlaying such issues is the basic challenge of defining the concept of sustainable engineering itself.

"Conceptually, it's slippery," Allenby says, "but it's crucial to gain an understanding of what is truly sustainable, and what contributes to system resiliency, if we're going to make the kind of effective advances in infrastructure engineering that rapid urbanization demands."