NAIROBI — In theory, the “women-only” option offered by the popular ride-hailing app sounded like a great idea to Sarah Maranga.

Maranga, a 34-year-old who lives in Nairobi, said she has been alarmed recently by reports of harassment and assault that women in Kenya’s capital have faced from male drivers. Among friends, stories of bad experiences are a common thread. And she’s had male drivers repeatedly call and text her after rides, apparently mistaking her friendliness for flirting.

So she liked the idea that Bolt — an international ride-hailing company that operates in Kenya — this month began offering the option to select female drivers.

Then she heard about the higher cost.

The prices haven’t been extraordinarily different, and sometimes they are the same. But the gap has been notable enough for Kenyans to take to social media since the launch Monday to complain about the added price of the women-only service, which some described as yet another “pink tax,” or extra charge in products intended for women.

“We are being charged more to feel safer,” Maranga said. “It seems like we are being punished for complaining.”

Bolt, which is based in the Baltic country of Estonia, said in a statement that it tries to match the price of a women-only ride with that of a standard ride, although a spokesman acknowledged that the actual cost varies according to demand and driver availability — and said that fewer than 5 percent of Bolt’s drivers in Nairobi are women.

Ride-hailing services catering specifically to women have been around for years, including in Brazil, Australia and the United States. Little, an e-taxi service in Kenya, started its women-only service — called “Lady Bug” — in 2016. Bolt has been rolling out its version in Africa since it launched in South Africa last year, the company’s East Africa regional manager, Kenneth Micah, said in a statement.

Price differences on a recent weekday morning were small but consistent, Washington Post reporters observed. A standard Bolt from Ngong Town to Nairobi’s central business district — about 12 miles — was about $9.46, for example, compared with $10.01 for a women-only ride. On Saturday afternoon, no drivers were available on the women-only service when Post reporters checked; the app said all were busy.

Malaika Cheyne, a 20-year-old student in Nairobi, was so upset by the cost discrepancies that she decided to cancel her Bolt account, describing the differential as “a pink tax at its finest.”

“Why should we have to pay extra so that we don’t get assaulted or abused or anything,” said Cheyne, who said she had been using Bolt recently because it tended to be less expensive than Uber.

Women bearing the cost of the bad behavior of men is in some ways a universal phenomenon, Cheyne said. But it has a particular resonance in Kenya, she said, because Kenyan women often feel that men disregard or minimize the problems women face. She was frustrated that when a woman in Nairobi recently accused a Bolt driver of stabbing her, the company put out a statement saying it was the passengers who attacked the driver.

Micah, the Bolt spokesman, said the launch of the women-only service “was not triggered by the recent assault [incident] that we strongly condemn” — as some on Twitter had speculated. He said the assault is being investigated by authorities. The women-only service, he added, is related to a broader women’s empowerment initiative.

The issue is about supply and demand, said George Gitoga, a part-time Uber driver whose tweet about Bolt’s pricing launched some of the social media debate.

He said he questions whether the women-only option will be successful, because many riders in Nairobi tend to go for the cheapest option and because — judging by what he has seen on social media — he’s not sure how many riders trust women to drive them, especially at night when the risks of a carjacking or robbery are higher.

“And no offense,” he added, “but they say women drive slowly.”

But there are many reasons women want to ride with other women, said Karungari Kahende, the head of partnerships at Little, which also operates in Uganda and Tanzania.

There are the security concerns, which she said have escalated for customers and drivers nationwide in recent years. (Little had not seen an increase in complaints, she said, but neither Little nor Bolt responded to questions about the number of complaints they receive.)

There also is simply the benefit of supporting other women. “It’s like, she is getting her grind on, and I want to empower her,” Kahende said.

Prices for the Lady Bug rides tend to be slightly higher than the standard, she said, largely because there is more demand than female drivers, who comprise 25 percent of the company’s total, can meet.

Dalmas Omia, a gender studies research fellow at the University of Nairobi, said that bringing female-only ride-hailing into Kenya’s male-dominated transportation sector is a noble idea.

But the higher price risks further “economic segregation,” he said, when ride-hailing is already not an option for many Kenyans.

The problem is somewhat circular, he said, with female drivers having many of the same fears about harassment and assault as female customers.

“It is almost like a vicious cycle,” said Maranga, the 34-year-old. “It seems like we are stuck.”

Rael Ombuor contributed to this report.

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