Here's a fascinating short film (about 10 minutes long) from National Geographic about the trans-Sahara railway in Mauritania. There's some great cinematography, but the story itself is one of commercial transformation in the midst of age-old tradition.
We forget how something as simple as a railway line can transform a culture, and perhaps a nation, over time. However, it can only do so much. At present, parts of Mauritania are plagued by the same instability and terrorism that are affecting the rest of the Sahel. Clearly, despite operating since 1963, the Mauritania Railway hasn't changed that.