CNG

This is also the refrain heard at the largest of the city's CNG filling stations near the airport.

The authorities, though, want more people to switch to CNG because it is a relatively clean-burning fossil fuel that results in fewer emissions of nearly all types of air pollutants, according to the UN.

However, the country manager of Taqa Arabia, an Egyptian company that runs the filling station near the airport, sees the growing demand as a "positive sign that CNG use has started to develop in Tanzania".

Egypt has pioneered the use of CNG on the continent, with about half a million vehicles converted to a dual-fuel system since the 1990s.

These measures should in the medium-term lead to shorter queues, but for the time being the lack of filling stations will continue to frustrate Tanzania's CNG pioneers.