If you read any Sherlock Holmes story and you won’t get far before you hear it in your imagination; that rattle of wheels, the clip of hooves on wet stones, the cry of “Cab, sir?” from the kerbside. London in the late Victorian years was full of noise, but the sound that carried furthest was the hansom cab. Holmes and Watson used them as naturally as we now use the Underground, and Conan Doyle rarely missed the chance to put his detective into one of those fast little two-wheeled carriages. The invention itself was down to Joseph Aloysius Hansom, an architect from Yorkshire who in 1834 came up with what he called a “safety cab.” The trick was simple: lower the centre of gravity, perch the driver behind and above the passenger compartment, and suddenly you had a vehicle that could take corners at speed without tipping over. Hansom didn’t make much from it—he sold his patent for ten pounds—but his name stuck, and by the middle of the century hansoms were everywhere in London. They were fast, they were light, and they became the Londoner’s idea of quick transport. Omnibuses plodded along on fixed routes, carriages were for the very rich, but a hansom—well, a hansom was the thing if you wanted to be across town in a hurry.
At its heart the hansom was a two-wheeled, horse-drawn cabriolet designed to be both swift and stable. The body measured about twelve feet in overall length, four and a half feet across, and stood roughly seven feet high. The large wheels, five feet in diameter, were set beneath the weight of the body to improve balance, while the whole construction weighed in at about twelve hundred pounds when unladen. A single strong horse of fifteen or sixteen hands was sufficient to pull it at a brisk nine or ten miles per hour — far faster than the heavier four-wheeled cabs that had dominated London’s streets earlier in the century. The cabin was intended for two passengers, though three could be squeezed inside at a pinch. Entry was through folding doors at the front, which the driver could operate by releasing a catch from his seat. Within, a padded leather bench stretched across the width of the vehicle, with sliding glass windows on either side and a smaller front pane for ventilation. The roof was rounded and waterproof, with a projecting storm board to shield passengers from the weather. Illumination was provided by oil lamps fixed to either side of the body, though later models sometimes made use of gas lighting. Communication between passenger and cabman was made possible through a trap in the roof, or more simply by rapping on the woodwork with a cane. Perhaps the most distinctive feature of the hansom was the elevated driver’s position. Unlike earlier cabs, where the driver sat in front of his fares, the cabman of a hansom was perched behind and above the cabin. From this high vantage point he controlled both the horse and the doors, while also being placed literally out of earshot unless spoken to directly. For safety, a hand-operated lever brake acted upon the wheel, giving the driver control when descending steep gradients or pulling up sharply in London’s crowded streets
Holmes certainly valued them. From A Study in Scarlet onwards, the hansom is almost a character in its own right. Right from the beginning of the short stories, in A scandal in Bohemia we see Holmes pursue Irene Adler in a Hansom cab, telling the driver "The Church of St. Monica," said I, "and half a sovereign if you reach it in twenty minutes." In The Speckled Band, they take a cab to Waterloo Station just in time to save Helen Stoners life.
In The Adventure of the Final Problem Watson dodges Moriarty’s agents, including a pursuit in hansom cabs through London’s streets. And Indeed, in the Empty House, the very first outing after Holmes’s return from the dead, what do he and Watson do? Leap into a hansom together, off to catch Moran in the act. The hansom really is Holmes’s natural element. In A Case of Identity Miss Sutherland goes to church in a hansom cab, with Hosmer angel following behind only to then vanish mysteriously when she reaches the church. The list goes on with hansom appearing in numerous stories including The Man with the Twisted Lip, the adventure of the second stain and the Valley of Fear. Conan Doyle was careful with these details. The whole system of London cabs was regulated under the Metropolitan Public Carriage Act of 1831. Every cab had to be licensed, every driver wore a numbered badge, and fares were fixed by law. We see in The Hound of the Baskervilles, when Holmes tracks a mysterious spy through the cab’s number straight out of real life. Scotland Yard kept registers of cab numbers; passengers used them to report quarrels, police used them to trace criminals. Cabmen’s recollections made it clear how tough the trade was. A cabman told the Morning Chronicle in 1850: “We work fifteen, sometimes sixteen hours. The horse must be fed before ourselves, for if he drops, we starve.” Another, interviewed by the Pall Mall Gazette in 1870, said: “We know all London’s secrets. We hear them through the trap. We keep silent, unless the police ask.” They didn’t always keep silent, of course. Police courts are full of their chatter. Disputes over fares, accusations of “padding the hoof” (deliberately taking the long way round), complaints of bilking passengers who leapt out and ran.