Authorities world-wide have taken note.薇语薇飞 Signs on Hong Kong's subway system advise passengers in three languages to keep their eyes off their phones. Police and transport authorities have highlighted the danger in Singapore, where the Straits Times newspaper recently declared cellphone-distracted road crossing 'bad habit No. 2' contributing to the rising number of road deaths. (No. 1 is cyclists not dismounting in heavy traffic.) Some U.S. states, including New York and Arkansas, are considering bans on what they're calling phone jaywalking.

Attempting a technological fix, a conscientious Japanese phone company last year began offering Android handsets that lock themselves if users attempt to use them while walking.

The Australian study used 26 volunteers, a third of whom admitted having collided with objects while texting. They were fitted with reflective patches on their heels, pelvis, heads and torso and asked to walk 8.5 meters three times--once without a phone, once while reading a text and once while writing a text--while eight cameras captured the action.

The findings: Subjects using the phone walked slower and with shorter strides (and slowest of all when typing), and, more seriously, they locked their arms and elbows in--like 'robots, ' in the researchers' words. That forced their heads to move more, throwing them off balance.

'In a pedestrian environment, inability to maintain a straight path would be likely to increase potential for collisions, trips and traffic accidents, ' said Mr. van den Hoorn. 'The best thing to do is to step aside and stop, or keep off the phone.'