A significant amount of African poverty is explained by the sheer length of time people spend travelling from place to place - to get to school, to their crops, to town, to fetch water and firewood. It's not uncommon for women to spend four hours a day carrying water, or for children to walk 10 miles each way to school and back. Every one of these hours is unproductive, in a land where survival often depends on time spent on agriculture.
Small wonder that the bicycle is as much a symbol of freedom in sub-Saharan Africa now as it was for women and workers in the Britain of Victorian times. With a bike, not only can you get around, but you can also carry heavier loads.
The problem is one of availability. There's no longer any real bicycle industry in Africa, and therefore bikes and spares are imported and a bicycle typically costs a quarter of a year's salary. Add to this the lack of access to credit, and the effect is to keep a bike out of reach even though it could earn its keep in quite a short time. As a result, where China has about three bikes for every 10 people, Africa has three for every 100.
There are agencies which are working on this. Afribike, based in South Africa, for example, offers cheap bikes and maintenance training. And the Xtracycle Access Foundation in the US makes "longtail" extensions that hugely increase bikes' load carrying capacity.
Maintenance is important. There are western initiatives which involve collecting used bikes in developed countries and sending them to Africa, but they work only if they are well maintained because African mud and dust play havoc with moving parts. So the organisation Re-cycle, for example, which has sent 7,000 British bikes to seven countries also trains local people as mechanics. Founder Merlin Matthews says: "You can replace a bearing now, or you'll be replacing the whole wheel in a year's time."
Matthews is critical of big scale development projects that concentrate on motorways and cars. "They don't take into account all of the other road users," he says. "Money should be spent to the benefit of the country as a whole."