From the article: Conventional wisdom suggests that cracks begin deep in the roadbed and gradually migrate upward, eventually breaking out on the asphalt surfac

From the article: Conventional wisdom suggests that cracks begin deep in the roadbed and gradually migrate upward, eventually breaking out on the asphalt surface. Not so, claims Halim. The cracks have already been created by the rollers, regardless of the temperature and asphalt mixture used. I would guess that the mechanism of action is that water gets through the cracks and erodes the underlayment.