Uber is testing out its cash service in Nairobi in an effort to capture more of the ride-hailing market.

The Uber app typically allows users to pay via credit or debit card, which is not a popular practice in Kenya. Some banks do not allow recurring billing on their cards, making it difficult for many people to sign up for the service.

With Uber Cash, however, users in Nairobi can now opt for cash payment when ordering a ride, and will not be forced to give credit card details.

Nairobi is the second city globally to have the service after Hyderabad in India, where it was launched three weeks ago.

Users can also use mobile money payments to settle bills with drivers, a method of payment that Africans are comfortable with, said Jambu Palaniappan, Uber's regional general manager for Eastern Europe, Middle East and Africa.

Palaniappan said that Uber had received numerous requests for the cash option.

"We have heard from drivers that this has been a requested feature," Palaniappan said. "This cash experiment in Nairobi will give us some great insights and help us develop our technology to best meet the needs of the local consumers."

Esther Kirigwi, an early Uber driver in Nairobi, was optimistic that the cash option will help the service generate more revenue. "We are expecting that in a week we will have more clients," she said.

Uber's growth in Nairobi has been the fastest in Africa, according to the company.

The average expected arrival time for Uber cars in Nairobi is 5.1 minutes, down from 11 minutes in January when it launched. That beats times for cities in highly industrialized countries, like Milan where the average arrival time is 6.4 minutes.

The improvement in arrival times for Nairobi is likely due to an increase in drivers joining the service.

"It is a life changing-experience for me because there is business always," Kirigwi said. "I am my own boss and I can work anytime I want."