Sorry for the ambigous wording in my explanation. I hope this makes it a bit clearer:
- vehicle 'ego' entered the intersection first
- both vehicles 'vehE' and 'vehW' yield to ego because of this
- the difference between vehE and vehW is that the path of vehE merges with ego and the path of vehW crosses with ego
- vehW can drive safely up the the point where both trajectories cross and wait there. The main assumption here is that ego will keep moving so vehW doesn't have to come to a stop at the stop line and can follow ego more smoothly (rather than actually stopping in the middle of the intersection).
- since the path of ego and vehE merge, vehE has to enter a car-following relationship with ego. Thus the speed of vehE is computed as the safe car-following speed by computing a "virtual gap" as dFollower - dLeader - leaderLength where
- dLeader is the distance from ego to the merging point (start of lane:oW_0)
- dFollower is the distance from vehE to the merging point
- due to the curved left-turn movement of 'ego' being longer, the virtual gap is negative and vehE stops outside the junction. Again, the assumption is that ego keeps moving after entering the intersection and vehE can follow in a smooth movement.
- with different geometries, you might also see a merging follower wait within the intersection if the leader suddenly stops.
regards,
Jakob