Related to my PR #260 and discussions from it

To make road lane agents capable of moving on the road without colliding (and with minimal processing cost) we need some extension of the current road lanes. I think current approach (with 1.5D roads) is good and seemingly extendable enough to get there.
in the PR I already have the code that works pretty well for moving on one lane

Here is my plan for lane merging - basically having one primary lane which is used to sync the agents - and secondaries that are merging to it
merging and diverging is really the same thing - but for the start or the end of the lane

To make intersections work - in addition to lane merging/diverging we need to also have intersection of 2 lanes.

and then the intersection as a whole would look like this

Also for both-direction lanes, like turn lanes, overtakes on the reverse lane, etc - we could do the same thing with primary/secondary for 2 lanes in both directions - and look for obstacles there when we decide if we could use the lane. I didn't look at it too closely though.