Last month, a woman riding a New York City bus was injured when a 300-lb. manhole cover beneath the vehicle exploded, piercing its floor and slamming into her leg. It was just one example of what can happen when a "manhole event" hurls one these heavy pieces of metal high into the sky.
Manholes explode because the infrastructure under most cities is old, susceptible to damage from temperature extremes, rainwater, winter road salt and rodents. TODAY national investigative correspondent Jeff Rossen went underground with a ComEd utility crew in Chicago to see firsthand the kind of work that's being done across the country to solve the problem before another person gets hurt.