I had never noticed that before. On Google maps, you can see parked cars but no cars actually driving. Except for a few they missed on the Bay Bridge. Maybe they erase them because they overlay the street names, and cars would make it harder to read?

Interesting. Looking at Google maps on my desktop, the cars on the surface roads are there but hard to see due to the 3D effect. The interstates are completely empty (impossible in Atlanta). The cars that show up best on surface streets are stuck at stoplights. An occasional car stopped on the shoulder shows up too. I looked at Google maps on my both iphone and ipad, and there I can see cars both on the road and on the interstate. The satellite view is also much more recent on the iphone (but there is no 3D Google Earth effect in that app). I see cars and trucks on the interstate in the Apple map app as well. It looks like they do something to get rid of movement.