[usrusr]

Are you sure that moving, oncoming traffic is seen as an obstacle under that definition?

The real trick against gridlock is to equate the switch to green not as "go", but as "go, once the previous wave has cleared the intersection". The "don't enter before there is room for your car on the far side" is only an optimization on top of that.

[friendzis]

I am not a lawyer so I may not be 100% correct. As far as I remember my driving classes and other resources (cannot quickly find exact provision), anything that is not part of road infrastructure (there are intentional obstacles to guide traffic) and causes vehicle to change speed/direction is an obstacle, so moving traffic kind of is. I understand that this particular provision is specifically there to prevent gridlocks and is never enforced in this particular situation.

The way traffic works is somewhat dependent on region. I can go to another city an hour away and already feel a bit alien traffic wise there. This is relevant in discussion on autonomous vehicles: in any foreseeable future we need them to coexist with human drivers and abide by unwritten "everyone drives like that here" rules.