"Stone arch bridges are amongst the strongest in the world. The technology has stood the test of time. The Romans built stone arch bridges and aqueducts with lime mortar more than twenty centuries ago. Arches and vaults were also the determining structural design element of churches and castles in the Middle Ages. There are stone arch bridges which have survived for hundreds and even thousands of years, and are still as strong today as when they were first constructed."
"The main reason that western countries moved away from stone arch bridges is because of the high labour costs involved in their construction. In industrialised countries, it is cheaper to use pre-stressed concrete rather than employ a lot of masons and casual labourers. In the economic environment of East Africa and the majority of developing countries, stone arch bridges provide a more affordable and practical option."
"A larger proportion of locally available resources are used in stone bridges as they can be built with local labour and stones. In contrast, raw materials and machines have to be imported for the construction of concrete bridges and specialized expertise is required. Compared to expensive aggregates, local stones are a strong, affordable material and they are often available in the vicinity (10-15 km) of the construction site. There is no need for expensive steel bars, aggregates, concrete or galvanised pipes that have to be hauled over long distances."
Stone arch bridges, a strong and cost effective technology for rural roads. A practical manual for local governments, BTC Uganda & Practical Action.