What's Actually Under the Road You Drive On

A modern highway isn't just asphalt on dirt — it's a three-foot-deep precision composite designed with physics models, GPS-guided machines, and climate-matched chemistry. This episode breaks down the hidden layers beneath the pavement: from compacted subgrade to sacrificial wearing course, the shift from empirical to mechanistic-empirical design, and the preservation strategies that can save billions. If you've ever wondered what makes a road last 30 years instead of 8, this is the episode for you.