In cities across the country, they've appeared seemingly out of nowhere, like mushrooms sprouting after a rainstorm. Dockless electric scooters — the latest sharing-economy disrupter — have been dumped, without warning, on sidewalks from San Francisco to Baltimore and Providence, as companies follow the Uber model of invading a city first and asking permission later.

In response, they've been met with cease-and-desist orders, after-the-fact regulation, outright bans, and even vigilante activism, as citizens have hurled the devices into rivers, set them on fire, buried them, or simply deposited them helpfully in trash cans.

Could Philly be next?

The answer, according to city officials, is maybe — but they're doing their best to not be taken by surprise.

Whereas officials had to scramble to catch up with other tech-industry invaders like Airbnb and Uber that rolled into the city well ahead of regulation, they're trying to get ahead of the scooter situation.

Aaron Ritz of Philadelphia's Office of Transportation and Infrastructure Services said that, beginning in January, the city made connections with many companies in the field — connections he thinks have discouraged them from charging ahead without authorization. Then, City Council passed an ordinance in June allowing for permitting and regulation of dockless scooters and bike shares, as well as any other "small vehicles" that may come into the market. Ritz expects that permitting process, developed with industry input, to be up and running by this fall.

"We wanted to make sure we weren't put in a situation — as some of our peers have been, and San Francisco is probably a good example — where somebody launched a program without any dialog with the municipality," Ritz said. "Those have generally proven to be problematic."

The scooters — which, unlike Philly's docked Indego bikes, have no dedicated parking — top out at 15 mph and are considered to be a "last-mile" solution, ideal for people who live or work in places that are just a bit inconvenient to public transportation. Rides, purchased via an app, are typically priced at $1 to start, plus 15 cents per minute. The companies take care of charging and maintaining the scooters, typically by paying gig workers $5 to $20 to take the scooters home, charge them, and return them to the streets.

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But the two-wheeled invasive species, while met with enthusiasm by many riders, has also been greeted with outrage by citizens and officials. They cite the chaotic parking of scooters on sidewalks, lawns, and driveways as litter at best and a safety hazard at worst. When three companies invaded San Francisco with scooters in one week this March, complaints flooded in from people who tripped on the idle scooters, dodged riders on the sidewalk, and found the contraptions blocking access to their businesses. The media declared Scootergeddon.

Bird, a Los Angeles-based company, pioneered the model — if it can be called a model — of scooter-storming cities without authorization, starting with Santa Monica, Calif., in September 2017. Since then, the company has expanded to 30 cities, according to its website, and been valued at $2 billion.

It's also been kicked out of some of those cities, at least temporarily.

City governments have responded in other ways — some more nimbly than others. Los Angeles was trying to negotiate with Bird, the Los Angeles Times reported, when the company went ahead and rolled out scooters there anyway. Denver has been impounding scooters, according to the Wall Street Journal, while Austin, Texas, and Washington have imposed caps on the number of scooters companies may operate. According to the Boston Globe, Bird in August pulled its scooters out of Somerville and Cambridge, Mass., after the cities issued cease-and-desist letters.

Citizen protests, often carried out one scooter at a time, represent a separate challenge. An Instagram feed, Bird Graveyard, is dedicated to documenting the destruction: scooters set aflame, heaved into the ocean or piled in trash cans.

Given the Bird backlash, some other scooter purveyors are promising a more civic-minded approach.

Skip, which operates in the District of Columbia and four West Coast cities, touts a modest claim to fame: "Skip is the only operator never to have been issued a cease-and-desist," one spokesperson noted.

Instead, the company works with city officials and community stakeholders before launching, chief executive Sanjay Dastoor said.

"We're excited to come to Philly," he said — though conversations with the city would determine the date of the launch here, how many scooters will be operating and where they'll be concentrated, as well as whether the company will offer discounted rides for those who qualify for food stamps or other public benefits.

Bird did not provide details on its plans to launch in the city, and Lime, another large operator, didn't respond to a request for comment. But Dastoor thinks he's leading a shift in this industry that may help make the arrival of scooters in Philly more orderly.

"If you look at the way Santa Monica and San Francisco have discussed the permit process, what they're calling rogue launching isn't very well received," he said. "I suspect some companies may be following our lead in working with the city first."

City Councilman Mark Squilla, who sponsored the legislation that could usher e-scooters into Philadelphia, now sees them as an inevitability. He just wants to manage the process, and is contemplating designated parking areas or requirements to lock scooters to poles or racks. (Skip scooters, at least, do come with built-in locking cables, though no city has yet made this a requirement, Dastoor said.) It's not yet clear how much the city will charge companies for permission to operate in the city, though officials said they intend to cover their costs rather than create a revenue stream.

"Done properly, it could be a big positive for the city," Squilla said. "It could be a complement to our existing bike-share program."

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Ritz said the goal is to provide Philadelphians with options. Still, he acknowledged concerns about introducing competition to Indego, as private companies may be able to undercut the city program's pricing.

Perhaps an even greater worry is the fickle, fast-changing nature of the market for dockless scooters and bikes.

Ritz and colleagues had eagerly watched the rollout of Ofo, a dockless bike-sharing program in Camden — but the company pulled out after just two months of what was supposed to be a six-month pilot run.

La Salle University also had high hopes for a dockless bike-share service launched on its campus in March, but spokesperson Alyssa Porambo said the service won't return in the fall because the provider, Spin, has pivoted toward scooters. "We are currently looking into some options," she said. "We are very interested in bringing a bike-share program back to campus."

Still, cycling advocates are embracing the potential to bring a new demographic into the fold, said Randy LoBasso, a spokesman for the Bicycle Coalition of Philadelphia.

"There was a lot of chatter before they showed up in these cities that they might be dangerous, and we haven't seen any of that come to fruition," LoBasso said. "The purpose of cycling is to create an alternative to a car, and, like bicycles, scooters do that, so we don't have a problem" with them.

Actually, San Francisco trauma and emergency medicine doctors are only just beginning to study the health hazards associated with e-scooters, the New York Times reported. One physician told the paper he was seeing five to 10 cases each week associated with the devices, some of them extremely serious.

Despite such looming concerns, Squilla said he's anxious to bring Philadelphia's scooter-permitting process online.

"I hope it's sooner than later," he said, "because eventually they're just going to come in anyway."