LINDSEY TANNER AP Medical Writer Electric scooter injuries have surged along with their popularity in the United States, nearly tripling over four years, researchers said in a study published Wednesday. Nearly 40,000 broken bones, head injuries, cuts and bruises resulting from scooter accidents were treated in U.S. emergency rooms from 2014 through 2018, the research showed. The scooter injury rate among the general U.S. population climbed from 6 per 100,000 to 19 per 100,000. Most occurred in riders aged 18 to 34, and most injured riders weren't hospitalized. For the study published in JAMA Surgery, researchers at the University of California, San Francisco, analyzed U.S. government data on nonfatal injuries treated in emergency rooms. "Improved rider safety measures and regulation"