if
there is no major reason for keeping the old SUMO
version, could you please update to SUMO 1.15 to check
if your problem persists? It could be a bug which had
been solved in the meantime.
I'm using sumo 1.6.0 and have a common problem with
merging.
Say I have a freeway (5 lanes) and a on-ramp (1
lane) that merge to the freeway's right most lane
the merging type (junction type) is zipper
The vehicles on the ramp, however, cannot drive
through the junction and wait infinitely, because
there are vehicles on the other freeway lanes. Those
freeway vehicles don't need to be on the right most
lane.. Any vehicle on any of the 5 lanes will block
the ramp vehicles.
An experiment I did is I closed the right-most lane
of the freeway, using sumo-gui. The issue persists.