De futuro urbanorum

At the time of my first paper in the BMJ on the immense advantage of a bicycle to a general practitioner needing to visit patients in central London I had covered only 6000 miles (9656 km), an average during those first exploratory three years of only 8 miles (12.8 km) per working day.¹ Now, 23 years and three bicycles later, the mileage is over 62 000 (100 000 km), which is nearly 2½ times round the earth or a quarter of the way to the moon.

An urban odyssey

These innumerable short journeys have added up to a small urban odyssey, which has been not only highly efficient but enjoyable. Once I had experienced the freedom of movement and saving of time provided by my bicycle it became increasingly unthinkable to return to the frustrating torpor of trying to use my car for the job that I was doing. The only excuses for my previous 13 car-bound years in general practice are that the car was the expected mode of transport and that the traffic had not begun to thicken. Also global warming was generally played down at that time as a distant, even hypothetical threat—a ploy of theorists who liked to scare people—but nothing to be taken too seriously. The picture now looks rather different. But I did not buy my first bike to help the atmosphere: I bought it for convenience, and for speed.

I hasten to say that my last two bicycles succumbed not to accident but to metal fatigue, once, fortunately, when I had just negotiated Hyde Park Corner. Silently they broke in two, the fault in each case being a design weakness in the middle of the single crossbar. And yet I have never weighed more than 10½ stone (147 lb, 66.7 kg), nor would I ever knowingly take a pothole at speed. But I do now have a double crossbar.

The early euphoria of overtaking Jaguars and BMWs has fortunately worn off, although it remains an agreeable if rather repetitive experience. And I am continually impressed, both in my car and on my bicycle, by the civility and consideration that most drivers show to each other in this city, despite what the media would have us believe. In this I include taxi drivers, who do London much credit.

Yet, given the increasing clinical and epidemiological evidence of the benefits of regular exercise, it is strange that so many doctors still waste so much time crawling around inner cities imprisoned in their cars. This does no good to them or to the environment, and if they tell their patients to exercise they could well attract the fair retort, “Physician, wheel thyself.”

Some scientific benefits

Cars consume 50 times more oxygen than cyclists per unit distance covered, producing carbon dioxide at a similar ratio. They also have a greater cooling problem, since they explode their fuel combined with air at 2000-2250°C,² which is over one third of the surface temperature of the sun (6000°C).³ Cyclists operate at only 37°C, and from the standpoint of physics are not heat engines but constant temperature energy converters more analogous to fuel cells.⁴ But we, too, have to keep cool, and our main system of heat dispersal takes up no extra space and is functionally—if not always socially—most elegant. In short, we evaporate. A London surgeon visiting a patient at Claridge’s was delicately reminded of this by the splendidly uniformed man on the hotel door, who said as he took his bicycle: “I’ll just walk her up and down a bit until she stops sweating, sir” (J H Lees Ferguson, personal communication).

We cyclists are, so far as is known, the most efficient movers in the solar system, for two main reasons:

• Unlike the birds and the bees and all limbed land animals, such as ants and pedestrians, we use almost no muscular energy in supporting our body weight

• Like frogs and toads, we convert chemical energy into mechanical work at about 25% efficiency,⁵ whereas cars achieve only 20% efficiency.⁴

Thus we combine a comparatively simple machine with a propulsion unit of quite staggering complexity. We of course have the advantage over cars of using biochemical and neuronal systems that have developed over 500 million years and been tested, often to destruction, under the most rigorous conditions. We move silently and cleanly about our towns or countryside at almost no risk to anyone else, and, which puts us even more on the side of the angels, we leave the air cleaner than we find it, thanks to the trapping of inspired particulate debris by the mucous sheet covering our bronchial and bronchiolar epithelium. We do not fume in traffic jams or add to them, and while that sluggish primate Homo urbanus vehiculo constrictus will no doubt be with us for some time yet, his days of dominance may well be numbered. We are seeing already in our towns the re-emergence of that earlier and more active subgroup of the species Homo se propellens and Puella se propellens, who steer towards a sustainable future and overtake on their bicycles.