Portal Notes
The portal is one of the most exiting new features in SP2 and makes for interesting sessions, however it does require a bit of common sense and understanding to use effectively. Here are some notes to keep in mind when using the portal.

AI end Emitted Trains
The biggest and most noteworthy limitation is the emitting of trains and how that relates to the route outside the portal. When emitting a train, the portal pushes it out vehicle by vehicle and that train is under total control of the portal until the last vehicle has been pushed out and reached a trigger around 50 metres in from the entrance. This means that until a train has left the portal's control, it is being moved along without regard to junctions/trains/signals out there on the map.

This can obviously become a problem with long trains. It wasn't really feasible to do this another way with integrated AI or anything too fancy. The portal does check its own track for presence of other trains, but it can't see outside signals/junctions.

Storage of Trains
A portal can remember a total of 16 consists. Up to 8 of those 16 consists can be set as being produced consists in Surveyor. This means that if a portal's consist storage has reached its capacity of 16 consists, it will still consume a train (if configured to do so), but that consumed train won't be remembered. When a consumed consist is emitted, it will be deleted from the portal's consist storage database so another consist can take its place if needed.

Emitting to Another Portal The portal allows you to specify another destination portal to emit consumed consists from. When specifying the destination portal, be very careful to ensure you get the name exactly right. The settings of whether or not trains can be emitted/consumed in the destination portal will not be considered with this option - the portal here will simply directly instruct the specifies remote portal to emit the consist, regardless of that remote portal's settings/restrictions.

Timing
When specifying delays in minutes for periodic consist emissions, the time is always done in real time and not game time. So regardless of whether you are running Trainz in real-time or an 8X clock, the portal will still wait in real time.

Portal is not a Drive-Thru
You are not meant to connect a track at the lower-end of the portal. There is nothing to stop you from doing so as we can't currently enforce that, but we do try to make it quite obvious. The same situation applies to the passenger platform on the wharf - it is meant to be accessed from one end and hopefully the shape of the wharf asset would have made this obvious.

Rejected Consists
If filtering of train consists is enabled or the portal is configured to not consume any consists, this means stray trains that enter the portal will be ignored. The portal should halt its own operations until the stray train has either been taken out by user or driven itself out. The portal will not get rid of stray rejected trains.

Orders on Exiting Trains
Once a train has finished being produced, the portal hands it over to its driver (one will be chosen at random if the consist doesn't have one) and then go on and follow driver commands as usual. If the driver has no commands to follow, the train will sit their idle blocking access to the portal until you either drive it out yourself or give it some orders.

Slow entry of Trainz under AI
When under AI driver control, the driver will appear to be entering the portal slowly at first. This is because it sees the end of the line ahead and is not going to rush in when the end of line is in sight (see my comments above on Drive-Thru). Once the first vehicle has reached a trigger some 50 metres in, the portal script takes over and it will push the train along and delete it vehicle by vehicle. You can drive in yourself going a bit faster than AI would and get away with it no problems, by going in at very high TGV-like speeds is tempting fate.