Private drivers in London do not have to take the legendary test that requires London’s black-cab drivers to memorize 25,000 streets and more than 20,000 landmarks. Here’s what the city’s cabbies have to say about the test and the rise of private drivers. (Karla Adam,Jason Aldag/The Washington Post)

With their distinctive design and reassuring engine rumble, London’s black cabs stand out — like fish and chips and Big Ben — among Britain’s most cherished icons.

London’s black-cab drivers believe they are the best in the world. And given their years of grueling study to earn the right to get behind the wheel in the British capital, it may well be true.

Black-cab drivers, many of whom earn a comfortable living, have all passed “the Knowledge,” the legendary test of London geography expertise that dates to the 19th century.

But as GPS technology and ride-hailing services such as Uber threaten taxi businesses in cities worldwide, perhaps nowhere is the clash as resonant as in London, where a battle is brewing between the ultimate in British tradition and a Silicon Valley giant symbolizing an age of innovation.

Demand for the Knowledge has dipped since Uber started its service in the city in 2012. According to official figures, between 2012 and 2014, the number of students signing up for the Knowledge fell by more than a third.

“It’s in serious danger of becoming a novelty vehicle,” said Malcolm Linskey, 70, who for more than three decades has run the Knowledge Point, one of London’s largest training schools for black-cab drivers. He said that demand for his beginner courses has halved since Uber arrived.

“The market share is dropping because less people are doing the Knowledge. I don’t want to say it, but it’s Uber. Why bother to do 3 1/2  years [of training] when you can do three weeks?” he said. He dazzled a reporter by asking where she lived, then connecting the address to landmarks across London as effortlessly as a child connecting dots in a coloring book.

The Knowledge requires students to memorize a mind-boggling 25,000 streets and 20,000-plus landmarks, including hotels, hospitals, theaters, museums, stadiums, housing estates, schools, universities, parks, pubs, police stations, prisons and places of worship. It takes, on average, three years to complete — about the same time as a law degree.

The city’s private-hire drivers, a category that includes Uber, are not required to pass the Knowledge. They rely instead on their smartphones’ GPS technology to help them ferry passengers about the city. It takes about three months to become licensed as a private-hire driver.

Unlike many other major cities, London does not limit the number of cabs. Although the city’s population has grown in recent years, the number of black-cab drivers has remained stable at about 25,000. By contrast, the number of private-hire drivers has risen in the past three years by more than a third to more than 92,000.

Steve McNamara, the general secretary of the Licensed Taxi Drivers Association, a trade body, said Uber has worsened congestion and air pollution and hit traditional cabbies’ earnings by about 10 percent in the daytime and by up to 25 percent at night.

“We are as much part of this community as red buses, and we are being threatened,” he said. “We don’t want cowboys running around clogging up our streets.”

Uber has expanded quickly since launching in Britain, and today it has 20,000 drivers in London alone. Its supporters say it has ushered in choice and convenience and is usually much cheaper. A recent trip in a black cab from the Waterloo train station to Heathrow Airport cost $102. The same trip via Uber cost $68.

Not that it has been an easy ride for Uber. Traditional taxi drivers throughout Europe have railed against the California company, arguing that it circumvents the rules adhered to by conventional taxis. Its services have been barred or scaled back in a number of countries including Spain, Belgium and France.

But change is in the air. The European Court of Justice is reviewing a case that could have widespread implications, as the court is expected to consider whether Uber is a digital service company or a transport company.

In London, a crackdown on Uber and other ride-hailing services could be looming with proposals that could tip the advantage back to black-cab drivers.

Transport for London, the city’s transportation authority, has proposed private-hire regulations that could address some of the criticisms of the black-cab industry. The industry says Uber is operating in a fashion similar to traditional cabs while bypassing regulations that apply to drivers of black cabs, such as learning the Knowledge or meeting strict vehicle specifications.

The proposals include a five-minute delay after booking a car and a ban on showing cars immediately available in the area — a feature Uber customers love. They would also require drivers to pass map reading and English-language tests.

The changes “would mean an end to the Uber you know and love,” Uber said in response. More than 200,000 people signed a petition opposing the changes.

Jo Bertram, Uber’s regional general manager for Britain, Ireland and Nordic countries, argued in favor of lightening the load on black cabs rather than increasing regulations for Uber.

“These plans seem to be trying to level the playing field between taxi and private hire by imposing additional burdens on private hire that result in the negative outcomes for both consumers and drivers, rather than looking at how can we make some of the regulations on black taxis less onerous, which is something we definitely support,” she said.

Some, including Conservative Party members of London’s City Hall, have suggested that black cabs and private-hire cars would be on a more equal footing if the Knowledge was significantly scaled back. It is an idea at which many black-cab drivers bristle. They say that satellite navigation software does not always update quickly enough and that poorly trained drivers are easily rattled by traffic jams and road closures.

“Yes, it’s an arduous process,” said Danny Smith, 30, who has been training full-time for more than two years to become a London cabbie, zipping up and down the capital’s narrow streets on his moped. On a recent day, he was at a Knowledge school, going over “runs” with other students, or “Knowledge boys and girls,” who were marking off the names of streets he was calling out on giant laminated maps.

He said he hoped that becoming a black-cab driver would mean a lifetime of work and a decent salary, something he didn’t think Uber offered its drivers, who held a small protest in London last month over falling pay.

Plus, for Smith there is a certain prestige about the profession. “To drive a London taxi is quite renowned,” he said.

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