The driver turned off the engine and got out. Together, they disappeared behind the car, while the rest of us waited. Waiting was something I was used to by then, and time was something I knew I would be spending a lot of on this trip. I was on my way to Abuja, where I would take another car north to Niger. There, I would get on the Trans-Sahelian Highway, which is reported to be the one of the few—if not the only—completed legs of the Trans-African Highway network, a system which, in theory, will someday interlink the continent, revolutionize travel and trade, and usher in a new era of road-fueled prosperity so great, it is hoped, that Nicholas Kristof will be out of a job.

It is one of many schemes for improving Africa’s notorious roads, which take countless lives in accidents every year. The carnage costs countries around 2 percent of their GDP, while the delays, paperwork and the rest end up costing much more. Not unlike America’s interstate system, this highway plan entails nine tarmac corridors crisscrossing the continent. The impact would surely be huge, and could well have other less salubrious effects too. So this, at least, was the guise for my trip: an investigation into the state of transport in West Africa. I wanted to travel across one of these new roads to see where it might be taking the continent, and how it might change things for better or worse.

But I was starting to see there was another good reason to be here, too, something I hadn’t fully realized until I arrived. Back in Lagos, I talked to a woman who had recently moved home to Nigeria from the U.S. And while life here is not always easy, she had no intention of leaving.

“Now,” she said, “whenever I go back to the States, I feel like everything there is so easy and safe. There are no smells, no texture. It’s almost like you’re not really living.”

Her words had been running through my mind ever since. I thought about them when I looked out the car window at th...