As it stands, Splitters will be split at 100%, 50/50 or 33/33/33 depending on the amount of connections. It would be very nice to be able to set a specific exits for a splitter to be a higher priority so that it will only split when the lane becomes saturated.
The same is also true for Mergers, it would be nice to set a priority so the other lanes will be paused unless there is a gap that the higher priority lane isn't filling.