In Tanzania’s remote villages, where rivers swell during rainy seasons, and roads disappear under floodwaters, a quiet engineering revolution is reshaping how communities stay connected, and it is being driven by stone.
At the centre of this shift is well-detailed by the Coordinator for stone technology, Engineer Pharles Ngeleja, from the Tanzania Rural and Urban Roads Agency (TARURA), and its headquarters in Dodoma.
Since 2017, TARURA has constructed 490 stone bridges across rural Tanzania for 40 billion shillings, saving the government more than 100 billion shillings compared with conventional concrete and culvert structures.
“Bridges are the economy,” Ngeleja said. “Without bridges, even the best road becomes useless.”
Tarura oversees a vast road network, including 1,449.77 kilometres of roads and bridges in Dodoma alone, one of the country's largest regional networks.
For Engineer Ngeleja, the challenge was not just building roads, but ensuring they remained passable year-round, especially in flood-prone rural areas where farmers, traders, and schoolchildren rely on safe crossings.
The solution, he said, lay in rethinking modern construction norms.
Stone bridges, built using carefully selected and tested masonry, cost four to six times less than reinforced concrete alternatives, can be completed more quickly, and use locally available materials.
They also cause less environmental disruption, aligning with Tanzania’s broader sustainability goals.
“All materials are tested in the laboratory,” Engineer Pharles explained. “The stones must meet a minimum material performance index of 25, and every stage of construction is closely supervised. If you compromise at any point, you compromise the bridge.”
While stone bridges may sound old-fashioned, Eng. Ngeleja points to their proven durability.
Across Asia and the United States, stone bridges have remained in service for centuries. Tanzania itself has stone railway bridges along the Central Railway Line, linking Mwanza, Dar es Salaam, and Kigoma, that are more than 100 years old and still operational.
“We did not invent this technology,” the engineer said. “We refined it and adapted it to our environment.”
A factor said had been a successive talk discussed at the COP 30 in Brazil, plus a recent Visit from West Africa last year, and a recent responsiveness of the world's nations to TARURA projects.
Since adopting the approach in 2017, TARURA's programme has transformed rural mobility, allowing roads to remain open during rainy seasons and improving access to markets, schools, and health facilities.
The cost savings have enabled the agency to redirect funds toward other development projects, multiplying the impact of limited public resources.
For engineer Ngeleja, the strategy reflects a broader shift in thinking.
“Development is not always about the most expensive solution,” he said. “Sometimes it is about the smartest one.”
As Tanzania continues to expand its rural road network, stone bridges are emerging not only as a technical solution but as a symbol of how local innovation, historical knowledge, and disciplined engineering can converge to deliver modern infrastructure at a fraction of the cost.