来看一下加州highway的法定定义

In the state of California, civil code 360(590) defines that a highway refers to "any way or place of whatever nature, publicly maintained and open to the use of the public for purposes of vehicular travel." Streets, avenues and even one lane dirt roads are therefore considered highways within the state of California, so long as they are maintained by the state. Multi-lane, high-speed roadways with restricted access are called freeways according to California's civil code, whereby all freeways are highways but not all highways are freeways.