Whenever travelling around Kampala, Uganda’s overcrowded capital, I ride boda bodas to source essentials unavailable at our home in the far north of the country.

A boda boda (the derivation is onomatopoeic, describing the rhythmic noise it makes) is a motorbike whose pillion seat is long enough for two passengers and their purchases.

The latter may include several trussed live hens, sacks of sesame seed and beans, and the occasional incontinent piglet. In a city gridlocked from 6am to 6pm, they are essential for affordable progress. Where a car may take up to an hour to travel a distance of two kilometres, the boda is there in 10 minutes.

The drivers are thin, usually unsmiling, and look either bored or worried. They are seldom over the age of 30, the attrition rate being high due to poor pay, the ceaseless competition for passengers, and the constant threat of instant dismissal by the boda owners.

The highway code they obey is simple – bodas give way to each other but not to four-wheeled transport; pavements can be used to speed up progress and also the opposite side of the road if oncoming cars hesitate for a moment; traffic lights are negotiable and traffic police ignored unless they are identified as close relatives; and car drivers are keenly aware that if they bump a bike, they will be surrounded by an indignant pod of boda drivers demanding reparations. They seldom come to a complete halt, their judgment of seemingly microscopic gaps in the traffic jams being remarkable.

If you can imagine Byres Road in Glasgow or Princes Street in Edinburgh with vehicles clogging all lanes and side streets, then add several hundred bodas, there you have Kampala.

Experienced passengers sit bolt upright, thighs glued to the bike, feet avoiding the exhaust pipe which melts plastic flip-flops and produces burns. Elbows should not protrude nor is it wise to look over your drivers’s shoulder at the chaos ahead as this may precipitate a panic attack.

You are not allowed to clutch the driver’s waist, however dire your state of balance, as any suspicion of gay behaviour is now a legal offence in the country. The fare for a trip in or around the city centre averages 70-80 pence if you look and behave like a normal stressed-out citizen but if you do not, this can rise logarithmically, hence the insistence that my teenage son accompanies me. He schools in the city, is proficient in several languages, and speaks in the present aggressive tense.

Unlike most of the global population, boda drivers in the city do not use mobile phones while working, joining a small band of heroes which include Channel swimmers, obstetricians delivering twins, and Tuscan wine farmers tramping grapes.

Their rural brothers up country are quite different, being co-operative and helpful even to non-passengers, tucking well into the correct side of the road, and often stopping to chat with friends for lengthy periods.

The loads they carry are impressive – enormous bundles of scythed grass for thatching huts, wooden poles and plastic guttering, sacks of charcoal for cooking – and often balanced on planks for equilibrium, which means they can occupy half the road. This discourages overtaking until your wife points out that the heavily loaded "lorry" which is threatening to make everyone late for lunch has only one rear wheel.

Dr David Vost studied medicine at Glasgow University and is currently working at a hospital in Swaziland. He and his family live on a small farm in northern Uganda near the Albert Nile. davidvostsz@gmail.com