Lime warns that its electric scooters can brake without warning

Lime is advising riders to be extra cautious because of a software glitch that can cause its electric scooters to brake unexpectedly, especially when going downhill fast.

The San Francisco startup recently detected a bug "in the firmware of our scooter fleet that under rare circumstances could cause sudden excessive braking during use," it said.

While infrequent, the potentially dangerous scenario was found to occur "usually riding downhill at top speed while hitting a pothole or other obstacle," Lime stated this weekend in a safety update. "Excessive brake force on the front wheel can occur, resulting in a scooter stopping unexpectedly," it said.

Lime is updating its software with a series of fixes that have already cut the number of braking incidents, the company said. Still, it's urging riders to give the brakes a "tight squeeze" as they start off to ensure their scooters are functioning properly.

The company said the glitch affected less than 0.0045 percent of all Lime rides, but acknowledged that "some riders have been injured."

Published reports suggest the problem could be more even prevalent. In New Zealand, for instance, two cities have temporarily banned Lime's electric scooters, including Auckland, where 155 incidents involving irregular braking were reported, injuring 30 people.

Lime was also forced to pull hundreds of scooters from two Swiss cities after several riders were hurt by locking brakes in Zurich and Basel, according to Swiss site The Local.

Lime is being sued by Texas man who reportedly was thrown onto a downtown Austin street earlier this month after the Lime scooter he was riding locked up, leaving him with a broken arm and strained shoulder.

"The best way I could describe it is that in the blink of an eye both wheels were super glued to the sidewalk, it was like a statue, and I was still moving," he told the American-Statesman on Thursday. 

Separately, Lime yanked thousands of scooters out of circulation last summer in California after learning that a small number might have held batteries with the potential to catch fire.

Companies like Lime, founded in 2017, and rival Bird have grown quickly in cities around the world as a transportation option to help commuters navigate the so-called last mile -- areas that are too far to walk to and too small for public transportation. That success has fueled speculation that Lime could go public this year in what would be one of the mostly highly anticipated stock offerings of the year.

Yet the popularity of electric scooters is also causing a headache for city officials puzzling over how to regulate the two-wheeled vehicles amid concerns about their safety. A recent Consumer Reports investigation estimated that 1,500 people around the U.S. had been injured in a scooter-related incident since late 2017.