The history—and future—of hitting the road

Today’s streets have it harder than their ancestors did. Instead of feet, hooves, and wooden wheels, they shoulder semis and SUVs. As we’ve developed new ways to zip around, we’ve also changed the makeup of the routes on which we travel, transforming gravel paths into asphalt superhighways. Challenges such as extreme weather and carbon emissions mean our expressways must evolve even further, so engineers are turning to futuristic fixes to keep traffic flowing. Here’s the story behind that long and winding journey—and where it’s going next.