Let's make most stop signs into yield signs, even for cars. Being on edge (alert) causes drivers to be focused, which reduces accidents. See roundabouts.
It means "yield to the right" (driving on the left), and presumably costs a similar amount to other markings painted on the road.
The one pictured has very poor visibility, so it's expected that drivers will almost-but-not-quite stop until they can see. [2] is more typical. A driver where the camera is can proceed, since they can see the other car is turning out of the junction and none are following it.
Large vehicles like buses can drive over the white dot, since it's just paint.
[1] http://www.sabre-roads.org.uk/wiki/images/7/75/Tiny_mini_rou...