"Some data suggests that at any given moment on the streets of America, 60 per cent of pedestrians are distracted while walking, meaning either on the phone or doing something on their phone," said Alan Hilibrand of the American Academy of Orthopaedic Surgeons. "It's a bit of a startling number."
Hilibrand, vice-chairman of orthopaedic surgery at Thomas Jefferson University Hospital in Philadelphia, has seen evidence of what he calls "digital deadwalkers" on central city streets.
"We've had people come into the emergency room who were hit by cars," he said. "They're looking at their phone and not paying attention to the fact that a vehicle is making a turn."
In a bizarre tragedy a few blocks from Hilibrand's hospital in May, a 68-year-old woman visiting from Texas was said to be looking down at her iPad as she crossed a street in the city's Chinatown. She was hit by an amphibious duck boat filled with tourists and died of head injuries.
As mobile devices have become more common, the number of emergency room visits by distracted walkers has climbed steadily. Some of the best information is a bit out of date, but it gives a sense of the trend. In 2005, 256 pedestrians in the US who were injured while using phones received hospital treatment, a number that grew sixfold by 2010.
"I would say the really rapid explosion and proliferation of these devices has taken off in the last five years, so I suspect the numbers have jumped quite a bit," said Hersman, whose National Safety Council compiled data from several different reports in its annual statistical safety profile.
One surprise was that more than half of injuries happened while people were fixated on their cellphones while walking in their homes.
Overall, more than two-thirds of the injured were women, and slightly more than half were under age 40. More than 20 per cent were age 71 or older.
"I do it if there's not a lot of people around," said Courtney Thomas, 32, when his communion with his cellphone was interrupted on 12th St NW, just below H St, in the District. "I've seen videos of people falling into fountains and running into signs, so I look up every couple of seconds."
One Chinese city, Chongqing, home to more than 9 million people, has put up satirical "no cellphone" lanes on the sidewalk to remind people their distraction can be dangerous and annoying.
A recent survey by the Pew Research Centre found that Americans have grown comfortable using their mobile devices in public, and nowhere more so than "while walking down the street", which 77 per cent said was generally okay.
"I was just checking something my brother sent me on email," said Cameron Ratliff, 27, as he crossed 11th St NW at G St recently. "Usually, if I look at it, it's when I'm stopped at a crosswalk. I've never run into anything."
Hersman said it's hard for most people to ignore their phones.
"We're dealing now with an addiction to these electronic devices that is, frankly, all-consuming," she said.
"When something beeps or buzzes or dings or vibrates, it really is as compelling as someone tapping you on the shoulder.
"People are being conditioned to engage in these activities, and they get immediate gratification for that. Our brains get a hit of dopamine every time we open a message."
Kwasi Frye, who works for a Washington firm that makes apps for mobile devices, was making his way down 11th St NW recently, his eyes fixed on his cellphone. He was asked whether he usually looks at his phone while moving down the sidewalk.
"Yeah," Frye said, "but unfortunately I don't have a lot of time to talk right now. Could we do this over email?"
