Yes, you can absolutely flag down a traditional "Black Cab" (Hackney Carriage) in London, provided the yellow "TAXI" sign on the roof is illuminated. If the light is on, the cab is available for hire; if it is dark, the driver is either already carrying a passenger or is on a break. To hail one, simply stand on the pavement where it is safe for the vehicle to pull over and extend your arm clearly. In 2026, while apps like "Free Now" and "Gett" have become popular for pre-booking, the ability to hail a cab on the street remains a protected legal right for Black Cabs that Uber and other private hire vehicles do not share. These drivers have all passed "The Knowledge," a rigorous test of London's 25,000 streets, ensuring they can navigate the city's complex layout without a GPS. All official Black Cabs are wheelchair accessible and are legally required to accept credit and debit card payments, making them one of the most reliable and iconic ways to traverse the city's historic and often congested central districts.