From #openttdcoop wiki
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For high traffic stations, it is necessary to separate the material drop station from the finished product pickup station.
- Wood Drop, Goods Pickup
- Iron Drop, Steel Pickup
- Factory Drop, Goods Pickup
- Oil Drop, Goods Pickup
In the early stages of the game, focus is placed on delivering the raw materials to the station. Generally, shipping the second-tier products (goods/steel) is delayed until more funds become available for developing the new station and additional mainlines to deliver these products. So the drop station is generally quite simple:
(insert image of simple station)
Inevitably, the second-tier drop (goods drop/factory) will be created, and a train will be sent to the drop station to get those goods. As more goods are produced, additional trains are created to carry the cargo. The problem arises when all or most of the drop platforms are full of trains waiting to pick up goods. Without sufficient platforms available for dropping the first-tier products, the second-tier products will not be produced, and will eventually cause serious backups or even deadlock:
(insert image of deadlocked drop station)
The solution is to separate the pickup and drop stations so the trains have minimal interference with each other. The drop station will have continuous movement of trains dropping off cargo, and the pickup station will contain trains awaiting the second-tier products:
(insert image containing both pickup and drop stations)
New Pickup Location
The primary advantage of creating a new pickup location is the simplicity of changing orders. In the cooperative game, there is usually a single drop point for each type of cargo. For second-tier products, all of the trains performing a pickup at the station will be going to the same drop station, so their orders are almost always shared. Changing the pickup station only requires changing one of these train's orders to replace the old pickup station (the drop station) with the new pickup station. Shared orders ensures all other trains receive these orders, and the change is complete.
The primary disadvantage of making a new pickup location is that the drop station will continue to receive a portion of the second-tier products. Historically, the rating for the second-tier cargo has been higher than the new station (which has no rating). Over time, the rating at the original station will drop; however, some of this cargo will still be placed on the platform in hopes that a train will come by to pick it up (which it never will). Over the course of 50+ years, the rating at the old station will drop to around 25% (rarely lower), and the platform will still contain this second-tier cargo. Attempting to move this cargo from the old station to the new station will only cause the rating of the old station to increase, and the cargo will continue to be shared between the two stations. Additionally, you'll have the overhead of several transfer trucks to move the cargo.
New Drop Location
The primary disadvantage of making a new drop location is the complexity of changing orders. Each raw material source has their own set of trains with shared orders. Changing the drop station will require a change to one train from each raw material station. In cases where there are 20 raw material sites, the change will require 20 order changes (assuming all trains for that route use shared orders).
This change of orders can be done within less than a game-year by just observing which trains come to the old station. Any dropping trains at the old station need an order change. Any trains without shared orders can be corrected. In the long run, a drop train going to the pickup station is not going to disrupt anything, it just won't be as profitable as it could be if it used the new station.
The primary advantage of making a new drop location is that the second-tier products are placed only on the original station, where they always have been. The industry will not distribute goods to both the new and old stations because there is no history of a second-tier train ever visiting the new station. No cargo will be lost.
Another (untested) way to separate the drop and pickup stations is through the use of waypoints. A single station can serve as both a pickup and drop station if enough platforms can be reserved for dropping trains and the queued pickup trains do not prevent the drop trains from reaching those platforms.
Waypoints are currently not able to span multiple tracks, so the use of stations is required. When using the "New Non-stop Handling" patch (enabled by default on cooperative games), marking a station as non-stop in the train order list will cause the train to use it as a waypoint, neither slowing down or stopping at that station. By adding these waypoint stations to the track, trains can be directed to specific lines, thus splitting the station into a drop area and a pickup area.
(image for split station with waypoint stations)
There are several advantages to this type of station:
- Only one station to expand to handle increased traffic
- If more drop or pickup stations are needed, platforms can be changed from one type to the other very simply.
(images showing conversion of lines from pickup to drop and vice-versa)
There are also some special considerations:
- The waypoint station must be added to the order list of all trains (present and future)
- The SL must be able to accomodate the increased traffic of a single station
- There must be ample waiting space for the pickup platforms to prevent queued pickup trains from blocking dropping trains