Check whether materials can share one V3 rail

Check each section of rail separately

Traffic changes whenever a rail gains or loses a material. The section before a merge carries less than the section after it. The section after a consumer removes an item may carry much less than the rail entering that factory. Treat every stretch between merges and splits as its own calculation.

In Update 1, use 480 items/min as the limit for a V3 rail. Add only the materials that are present on the section you are checking. Do not use the total output of every factory connected anywhere on the route.

Draw the rail as a simple line and mark each merge, split, producer, and consumer. Once those points are marked, check each short section between them.

Use sustained demand, not maximum machine output

For each material, use the amount downstream machines need each minute while the factory is running normally. If a group of machines can make 120 items/min but its consumers only need 70, the planned rail flow is 70 items/min. Counting all 120 would make the rail look busier than the factory requires.

Only combine rates that can occur at the same time. If one temporary line is always shut down while another runs, they do not both need full capacity at once. Leave one line out only if you know the two will never run together.

As a simple example, three materials at 140, 90, and 60 items/min put 290 items/min on the shared section. That leaves 190 items/min unused on a V3 rail. The spare amount can absorb uneven arrivals and gives you room for a known expansion.

1. Mark the start and end of the rail section.
2. List every material present on that section.
3. Write down each material's simultaneous sustained rate.
4. Add the rates and subtract the total from 480 items/min.
5. Repeat the check after the next merge or split.

Leave room instead of planning exactly to 480

A total below 480 does not guarantee that every item will arrive smoothly. Materials may reach a merge in uneven groups, and a backed-up output can interfere with other traffic. Leaving some capacity unused makes the rail more tolerant of those conditions.

There is no single spare-capacity percentage that fits every layout. Leave more room on a long shared route with several merges. A short local rail with two steady inputs can usually be planned more tightly. If the only way a design passes is by using exactly 480 items/min, it has no room for a calculation error or future consumer.

Do not send an item past its consumer and then bring it back on the same route. Backtracking makes the traffic harder to count and can load a rail section twice for no useful reason.

Test the finished rail while the factories are running

After building the route, run the connected factories together and watch the storage on both sides. A receiving depot that keeps falling points to a delivery problem or an upstream shortage. A sender that stays full while the receiver empties points more strongly at the rail.

If the receiving depot still empties, compare each planned rate with what is actually arriving. Check for a missed material, an unexpected merge, blocked outputs, or a producer that is not keeping up. Split the rail when the real route cannot carry the load reliably, even if the arithmetic looked acceptable.