When Elliot Caroom moved to New York City last fall, among his worries were finding a place to live and, perhaps, running into the occasional person who might do "disturbing" things on the subway. Now, a new and more mechanical menace towers above all others.
"I didn't really think about it until a few crane incidents a few months back," Caroom said. "I'm naturally somewhat paranoid, so I started to notice more cranes, glancing upward, and at this point, it has become more serious."
Although he looks up "nervously" each time he passes by a crane, the 26-year-old graduate student acknowledges the irrationality of it all, adding that there's probably a stronger likelihood of being involved in a plane crash than a crane accident.
Still, psychologists find that such fears are fairly common, since certain aspects of big city life tend to trigger deeper anxieties.
Fred Newman, director of the White Plains Anxiety and Phobia Treatment Center, says dangerous situations that may be dramatic, involve many people at once or invoke a sense of being trapped, and are perceived by many to be "much scarier" than those situations that don't.
"Bridges, tunnels, closed-in spaces, like elevators, and large crowds are the type of places where people would be more likely to feel that way, because catastrophic things can happen," Newman said.
And as the population of a big city grows, so does the strain on its infrastructure.
"The cranes are there because they're expanding housing and office space, so demands on older systems are increasing," said Patrick Natale, executive director of the American Society of Civil Engineers.
Recently, as the wear and tear of old infrastructures start to show, these fears are starting to be realized.
In July 2007, an 83-year-old steam pipe burst in the busy midtown section of Manhattan. In the aftermath of the explosion, which killed one and injured 45 people, concerns surfaced about the condition of a water infrastructure system that has been creaking along since 1882.
A month later, the I-35W River Bridge in Minnesota collapsed, leaving 13 dead and more than 100 injured. The bridge, which government inspectors found to be "structurally deficient" in 1990, and again in 2005, had been slated to receive a steel reinforcement upgrade, but the project was scrapped in favor of periodic safety inspections.
"Our approach in this country to these problems has been a patch-and-pray mentality -- let's patch it up and pray that it lasts, instead of a good strong plan to make it right," said Natale, adding that "structures will break" if cities continue to operate this way.
In 2005, the American Society of Civil Engineers reported that more than a quarter of U.S. bridges are "structurally deficient." The group also estimated that $1.6 trillion would be needed over the span of five years to bring the nation's water infrastructure to a level where it can hold up to the demands of modern societies.
Brian Mergelas, a water pipe expert, points out that many threats to big cities, posed by aging water infrastructure, might not be as dramatic as a pipe explosion, but they are no less hazardous.
Sinkholes, for instance, can happen when a broken pipe gradually sucks away soil, weakening land to the point of collapse. Such sudden urban pits have been known to swallow cars, large trucks and pedestrians.