[chongli]

Yeah. It's the vehicle weight combined with temperature fluctuations and water, ice, and salt. The worst case scenario is when the road develops tiny cracks that fill up with water and then the temperature drops, causing the water to freeze and expand inside those cracks. The cracks grow larger and then when the water thaws and evaporates it leaves behind those large cracks/voids which heavy vehicles collapse due to their weight, turning cracks into potholes.