California has required dealers to put temporary license plates with unique IDs on all cars that don't already have license plates.
The change took effect January 1, 2019: https://us.dealertrack.com/content/dealertrack/en/landing-pa...
The change took effect January 1, 2019: https://us.dealertrack.com/content/dealertrack/en/landing-pa...
California has some mile posts and some numbered exits, but you're expected to report location by named exit. Ex: North on the 405, right after Pico Boulevard. Etc.
The California highway system was extensive before federal highway standards were developed, and California was exempted from exit number requirements. In ~2000, California decided to add exit numbers 'over the next ten years' as signs are replaced; twenty years later, it's still not complete, but Google still likes to give directions with exit numbers only, as if that were useful.