But the state has yet to pass any rules to encourage cooler pavement on its roads, which are largely coated with heat-absorbing asphalt, a cheap byproduct of oil refining.

• 然而，加州也将不得不通过立法来促使路面利用降温材料。目前该州的路面铺着大量吸收热量的沥青。沥青是石油冶炼过程中产生的廉价副产品。