AUSTIN, Texas – Narrow, motorized scooters whisking riders around cities like Austin and Los Angeles are meant to alleviate traffic congestion, encourage public transit and offer a cheap transportation alternative.

But critics also claim riders imperil pedestrians by driving the scooters on sidewalks and ignoring traffic rules, and emergency rooms have reported an array of scooter-crash-related injuries.

Now, the Centers for Disease Control and Prevention are studying the “dockless scooters” – so called because they can be picked up and dropped off anywhere – to better understand the machine’s health and safety risks. In the first-ever study of its kind in the U.S., a team of CDC epidemiologists arrived in Austin last week to investigate the circumstances that lead to scooter crashes and how best to prevent them. They're teaming up with Austin health and transportation officials.

The study will focus on EMS calls and emergency room data related to scooter crashes reported over a 90-day period, from September through the end of November, said Dr. Philip Huang, medical director and health authority for Austin Public Health, which requested the CDC query.

The CDC epidemiologists will review the data and interview people involved in the crashes to determine how the crashes occurred and offer preventive measures, he said. That information could lead to a new set of city rules for scooter riders. The study's results will be made public in the spring.

"We realized we wanted to get a better handle of the magnitude of injuries and the factors associated with the injuries," Huang said. "It's so new, we really don’t know very much about it."

Motorized, dockless scooters exploded onto city streets in 2016 and have proliferated in cities like Austin, San Francisco and Los Angeles as a cheap, easy-to-use transportation option. The electric scooters, from companies like Bird and Lime, are available to rent using apps on smart phones.

In Austin, seven companies have won licenses to operate 11,000 scooters throughout the city. In October, riders took 275,300 trips on the scooters, covering 264,300 miles, according to a report by the Austin City Council's Mobility Committee. In that same time period, the city reported only 14 scooter crashes with nine injuries and no fatalities, according to the report.

The scooters offer a cheap travel alternative in urban areas like Austin, which is growing and struggling to alleviate massive traffic congestion, said Jason JonMichael, Austin Transportation Department assistant director. Transportation officials have been encouraged by rows of scooters left at bus and metrorail stations – a sign that riders are using the scooters to reach public transportation, he said.

That's key in a city like Austin, which lacks a subway or metro infrastructure like New York or Chicago, he said.

"It's added essentially a full-on, New York-level transit line worth of service," JonMichael said. "It's given us the equivalent of high-capacity transit."

But some have complained of scooter riders zipping past them on sidewalks or traveling the wrong way on roads. On the campus of the University of Texas at Austin, scores of students motor around on the scooters. UT officials recently set up a committee to review their campus-wide policies related to scooters.

From Sept. 1 through Dec. 3, officials at University Health Services, an on-campus primary-care clinic for students counted 110 scooter-related injuries, including bruises, cuts, head injuries, sprained ankles and some fractures, said Dr. Melinda McMichael, the center's interim director.

"We weren’t seeing these kind of numbers with scooter accidents a year ago," she said. "It's concerning."

Another common complaint: Clumps of scooters left on sidewalks or in front of businesses. Austin launched a pilot program in April that mandates licenses and scooter limits for companies to operate in the city, but few enforceable rules exist for riders.

Councilwoman Ann Kitchen, who chairs the Mobility Committee, said she acknowledges the scooters' benefits but said the parking complaints and safety concerns need to be addressed. The CDC study should help with that, she said.

"One of the key things the city has to figure out is where is it appropriate for scooters to be ridden," Kitchen said. "We're learning a lot now through this pilot."

Austin's not alone as it wrestles with how best to live with the scooters. San Francisco issued a temporary ban, then limited the number of operators to two, while Santa Monica, California, is experimenting with designating some street parking spaces for scooter parking. Other metropolitan areas, such as Nashville, Tennessee, Denver and Washington, D.C., have tried similar approaches.

The scooter phenomenon is the latest "disrupter technology" in transportation and is showing many of the growing pains seen when ride-sharing companies like Uber and Lyft first came on the scene, said Susan Shaheen, co-director of the University of California, Berkeley's Transportation Sustainability Research Center.

A key difference, however, is the speed in which scooters have come on the scene and their widespread acceptance by users, she said. Another key difference: The speed by which cities are tackling the problem and sharing information with one another.

Dockless scooters are part of a larger conversation as cities continue to grow and city leaders and companies search for ways to move the masses around, Shaheen said. One sign that the scooters may be here to stay: Uber bought Jump scooters and is reportedly in talks to acquire Bird, another large scooter operator, she said.

"It's almost like you have to look at a broader range of options to keep people moving, and happy," she said.

Contributing: Chris Woodyard, USA TODAY.

Follow Jervis on Twitter: @MrRJervis.