Open this photo in gallery Women ride shared electric scooters in Santa Monica, Calif., on July 13, 2018. ROBYN BECK/GETTY IMAGES

West Hollywood city councillor John Heilman was heading to a grocery store when he noticed a blind pedestrian walking into the path of an electric scooter abandoned on the sidewalk. He moved it out of the way just in time.

The next day, Mr. Heilman voted to ban electric scooters from the streets of his Southern California city. “I like walking and I like running on the sidewalk,” he said. “And I like being able to do that without running the risk that somebody on a scooter is going to run into me.”

West Hollywood is the latest U.S. city to be pulled into what has become an epic battle over Silicon Valley’s hottest new investment: electric scooters. The rental devices have been flooding sidewalks and bike lanes across the country since they first began appearing across California late last year, and have become a sensation among tech investors, with some scooter startups now worth billions. They have also inspired a competitive cottage industry of “juicers” – residents paid to collect scooters from the street each night and charge them in their homes. Yet, despite their reputation as an overnight success, scooters have emerged as one of the most controversial transportation devices in years.

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They have enraged pedestrians, who have been startled by riders flying past them at high speeds, or have tripped over scooters left abandoned on sidewalks. Cities including San Francisco, Denver and Milwaukee have banned the devices while they figure out how to regulate them, and Canadian cities may soon be grappling with these issues. Scooter companies have posted jobs in Vancouver, Calgary and Toronto, where they have begun negotiating with city officials to expand their rental services. “It will be a matter of months before someone starts deploying there,” says Euwyn Poon, a Vancouver native who co-founded San Francisco scooter-sharing company Spin.

We just see [scooters] as another tool in the toolbox. — Thomas Thivener, a project co-ordinator in Calgary’s transportation department

On Monday, Calgary is set to approve a two-year pilot project that would allow companies to rent out up to 10,000 devices. The pilot would start with bikes and aim to include electric scooters starting in the first quarter of next year, though they would require an exemption from provincial transportation laws.

“We just see [scooters] as another tool in the toolbox,” said Thomas Thivener, a project co-ordinator in Calgary’s transportation department. “There is such a pro-business mentality in Calgary that we should facilitate these types of new technologies, and especially things that assist with mobility.”

Toronto officials are watching the U.S. scooter debate with more caution. “City staff have concerns for the potential impacts of these vehicles on pedestrians and the safety of these vehicles,” Jacquelyn Hayward Gulati, Toronto’s acting director of transportation infrastructure management, said in an e-mailed statement.

For all their controversy, the scooters are relatively simple – a two-wheeled skateboard with a handlebar that can travel at speeds up to 24 km/h.

The scooters are “dockless,” meaning riders can leave them anywhere. Riders locate the GPS-enabled scooters on an app, and are typically charged as little as $1 to unlock the device and 15 cents a minute to ride.

In the past, bike-sharing operations often operated as public-private partnerships and relied on local government funding to stay afloat. That’s not the case with scooters, which have been inundated with cash from Silicon Valley investors and ride-share companies such as Uber and Lyft. Uber was among the investors who recently poured US$335-million into scooter company Lime in July, valuing the company at more than US$1-billion.

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Open this photo in gallery A Lime electric scooter is parked on a street in Santa Monica, Calif., on July 13, 2018. Scooter startups such as Lime allow riders to park them anywhere that doesn't block pedestrian walkways. ROBYN BECK/GETTY IMAGES

“It’s all these data companies putting billions of dollars into whatever the new, exciting product is,” said Kate Fillin-Yeh director of strategy at the National Association of City Transportation Officials. “The amount of money that’s coming in has really changed the equation.”

A former lawyer who also runs a venture capital fund, Mr. Poon was inspired to launch Spin after seeing the popularity of dockless bike-sharing companies on business trips to China. When Spin started early last year it focused entirely on renting bicycles. Now Mr. Poon is planning to replace his entire fleet with the more-profitable scooters. “We get five times the number of rides just on the electric scooters,” he says.

The industry and its legions of fans argue that scooters offer a cheap, convenient and environmentally friendly alternative to cars. But some scooter companies have irked local governments by showing up in cities without warning, forcing municipalities to scramble to devise regulations.

Some transportation experts are skeptical that scooters will dramatically cut down on car trips, but say they have potential as part of a growing mix of commuter options that help to solve the “last-mile” problem – the gap between areas served by public transit and most riders’ ultimate destinations.

“These devices are showing people how many short trips they’re really doing that they maybe don’t have to take a car with,” said Madeline Brozen, assistant director of the Institute for Transportation Studies at the University of California, Los Angeles.

Companies have yet to give cities much ridership data to help them know whether the devices are replacing car trips, or are taking the place of walking or riding transit. The industry also operates on an opaque business model, Ms. Fillin-Yeh said, and companies have offered up scant details about whether their operations are actually profitable or whether the scooter trend may turn out to be a fad.

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“There is a fair deal of Silicon Valley optimism underlying this,” she said. “It’s really just a question of what happens when this optimism goes away and the money runs dry.”

Mr. Poon sees it differently. “Scooters,” he says, “will one day be as ubiquitous as cars.”