Pedestrians have been banned from looking at their mobile phones while crossing the street in Honolulu.
Hawaiian authorities say the aim is to reduce injuries and deaths from “distracted walking”.
Anyone found looking at their phone faces a fine of between £11 and £75 depending on how many times police catch them.
Mayor Kirk Caldwell said: “We hold the unfortunate distinction of being a major city with more pedestrians being hit in crosswalks, particularly our seniors, than almost any other city in the country.”
Anyone making calls for emergency services will be exempt from the fine.
Phone-related distractions while walking resulted in more than 11,000 injuries in the United States between 2000 and 2011, according to a University of Maryland study published in 2015.
The National Safety Council added “distracted walking” to its annual compilation of the biggest risks for unintentional injuries and deaths in the United States.
Council spokeswoman Maureen Vogel said: “Cell phones are not just pervading our roadways but pervading our sidewalks too.”
A number of initiatives have been introduced around the world to reduce injuries sustained by “smartphone zombies” who cannot tear themselves away from their devices.
An experiment in London saw lampposts padded to soften the blow for walkers staring at their devices.
The city of Augsburg in Germany last year embedded traffic signals into the ground near tram tracks to help mobile-obsessed pedestrians avoid injury.
Opponents of the Honolulu law argue that it infringes on personal freedom.
Resident Ben Robinson told the city council in a written testimony: “Scrap this intrusive bill, provide more education to citizens about responsible electronics usage, and allow law enforcement to focus on larger issues.”