Factorio Main Bus: Materials to Carry and Priority Order

The tricky part of a main bus in in Japan is that "carrying everything seems easier," but in reality copper wire and circuit boards clog it all at once. This guide, based on Factorio vanilla v2.0, organizes what to flow through your main bus and in what order—from highest priority to not recommended—in a way that holds up even with Space Age.

I learned this the hard way after red and green science (Automation and Logistic Science Packs). Two copper plate lines dried up instantly, and I felt the crushing appetite of green circuits. Starting from a baseline of yellow belts at 15/s, red belts at 30/s, 48 stone furnaces for yellow plate, and 24 steel furnaces for yellow plate, I began with 2 lines each of iron and copper plates and switched copper wire to on-site production and electronic circuits to a single completed-goods line. Suddenly the whole factory stabilized.

The core idea is simple: rather than cramming everything onto the bus from the start, secure thick plate supply and split the bloated intermediate products by role. Let's walk through how to decide on copper wire, gears, and electronic circuits—whether to put them on the bus, produce them on-site, or give them dedicated lines—and tie it all to practical workflows.

Factorio Main Bus Materials: Conclusion and Priority Order

The Four-Stage Decision Framework

When you're unsure what to put on your main bus, cut it down by asking: "Is it used widely across multiple lines?" "Does it flow better as a finished product than as raw materials?" "Is demand concentrated in one area?" "Would it make sense to make it right there?" Honestly, I've made the mistake of being fuzzy about this and just kept adding items until the bus was wide but unusable. The real secret is splitting "staple foods shared by the whole factory" from "side dishes made locally."

Given that foundation, here's what vanilla v2.0 boils down to:

Not putting copper wire on the bus is critically important. One copper plate becomes two copper wires—you're deliberately shipping the same function in a fatter form. Electronic circuits tend to clog right here, and I initially thought "shared intermediates would be convenient," ran copper wire for a while, then had to rip it out because the belt count just kept growing.

By contrast, running finished electronic circuits on the bus has real value. While you could feed iron plates and copper wire right there, the huge demand means each local production setup scatters the copper plate and iron plate routing. With 1 iron plate and 3 copper wires per circuit, a dedicated circuit line is a copper hog anyway. Making them in one place and running the finished product is cleaner for the whole factory.

Gears are a tough call. They look like a bus candidate by breadth of use, but they're cheap to make right from plates and don't cause headaches if you build them next to their consumers. I lean toward on-site production for gears, especially for beginners. Only feed them to the main bus if multiple lines in one area are using them continuously.

Petroleum-derived plastic, sulfur, and batteries depend more on how independently you treat your oil refinery as a production zone than on whether they should ride the bus. If circuits and batteries scatter across many lines, bus delivery is nice. But bunching your chemical plants into one cluster with dedicated supply is just as valid. Judge by whether demand scatters or clumps—that keeps you from flip-flopping.

Early-Game Template

An easy shape to start with is 4 belts per group with 2-tile gaps between groups, fed from upstream with priority materials in order. This spacing makes underground belts and crossovers simpler to route and easier to read later. The overall main bus thinking follows the pattern at Factorio Wiki: Tutorial:Main bus|Factorio Wiki's main bus tutorial.

My starting template would be:

1. Iron plates (2 lines)
2. Copper plates (2 lines)
3. Steel (1 line)
4. Electronic circuits (1 line)

This order scales very naturally from early to mid-game. The feel-good approach is: start with just 2 iron and 2 copper, add steel when you need it, then add circuits later. That's the gentlest growth I've found. Piling in red circuits or plastic before you use them just wastes corridor space.

Iron and copper need to be generous because yellow belts run 15 items/second, and 48 stone furnaces fill one yellow belt. Early on, "one belt looks like enough," but circuits, ammo, inserters, and belt parts all spike at once. I hit copper shortages hard during red-green science until I stopped being stingy with copper plates. Plan for the play-through you're aiming at, not just survival.

Steel is good at 1 line early—it's stable even if it trails plate production. 24 steel furnaces fill a yellow belt, so it scales easily. Electronic circuits, though, should branch into a "finished goods line" as soon as demand appears; that setup bridges to red and blue circuits later.

Red and blue circuits slot in as a second group of 1 line each once you're past this template. But no obligation if they're concentrated demand—run them local if one production zone dominates.

Tutorial:Main bus

wiki.factorio.com

Version Note and Caveats

This priority ranking assumes Factorio vanilla v2.0, with 2.0.73 as a confirmed stable version. The main bus concept doesn't shift fundamentally, but the article is tuned to "run past rocket launch comfortably." Space Age changes specs and recommendations by DLC/mod; if you detail specific mechanics (inter-planetary transport numbers, mod-specific rigs), cite those sources clearly. Reference example: Hoo's integration approach (https://note.com/hoo3863/n/n3de93e1891e7).

Vanilla works the same way: as factories grow mid- to large-scale, one main bus stops being enough. Steel mass production, circuit mega-lines, petroleum derivatives—these deserve dedicated lines or off-site handling. Trains and robot logistics come next. I like trains, and getting this cutover wrong is genuinely painful. The main bus is strong, but it's not a forever strategy.

So the conclusion here isn't "load everything on the bus," but "center your bus around iron, copper, steel, and finished electronic circuits, then add red circuits based on demand spread." That keeps vanilla v2.0 stable and the thinking translates to Space Age's wider scope.

Foundations: The Main Bus Is Not a Highway for Everything|https://www.jartic.or.jp/

Purpose and Scope of the Main Bus

A main bus is a design methodology: flow key materials in one direction, branch off where needed. The point isn't "optimal transport" alone—it's keeping the factory readable and making future production lines easy to add. That visibility is huge in early-to-mid game as you're scaling up.

But overusing the highway metaphor breaks things. Think of the main bus not as "a multi-use freeway," but as the backbone that widely shared materials ride. Iron plates, copper plates, steel, finished electronic circuits? Great—wide use, strong compatibility. Copper wire, though? It balloons in volume; once you cram that onto the main bus for visibility, you've undermined the whole point.

The Factorio Wiki: Tutorial:Main bus|tutorial frames the main bus as consolidating major resources. I used to think "lay out all materials I need and management is solved," but in practice, you hit limits fast. Adding items after the bus is built is painful—the bus is wide, awkward to expand, and eats real estate. Stuffing low-value items on it just makes things hard to read.

This tension is clearest once circuits and petroleum start scaling. A selective main bus is super clean, but trying to handle every output or every dependency on it defeats the purpose. You feed a main bus for clarity and extensibility, not to funnel all factory traffic into one place. That's the key insight.

Later-Game Alternatives

Once factories hit mid-scale, a single main bus can't prop everything up. There's only so wide you can go, and you need more and more items. Special lines for big consumers, distant ore sites, massive intermediate production—none of it fits well.

At that point, treat the main bus as the organizing tool for your factory core and hand heavy logistics to other methods. Trains and robots are the standards. Trains excel at distance and bulk; robots handle local top-ups and fine routing. The reason mid-scale factories usually _switch away_ from pure main bus thinking isn't because buses fail—it's because shrinking what the bus does preserves its strengths.

I've bitten the bullet many times: wanting to add more lines on either side of a set main bus, running out of space, and realizing it was faster to plant a train station on one side to feed bulk materials than to expand the bus. You can feed plates to a central station, then branch local buses or dedicated lines from there. The cargo bottleneck vanishes.

Robots work the same way. Rather than flying every item, use them as "the bridge for low-volume, high-variety needs." Main bus = thick trunk, trains = distance, robots = fine connections. The job division gets clean fast.

Space Age Perspective

Space Age makes this "don't put everything on the bus" thinking almost inevitable. You don't need to stretch one main bus philosophy across planets and factories. Instead, make a local bus per site and connect sites with trains or robots.

Even in Space Age's design philosophy—as seen in examples like Hoo's setup—the takeaway is that you don't load the same bus as hard. Locally, it's still strong. But dragging it across inter-planetary or mega-region distances just adds pain.

The sweet spot: Each site gets its bus for local clarity; sites talk to each other via trains or bots. The "big backbone" becomes "local organizing tool." Hybrid design—bus locally, trains or robots between nodes—survives expansion way better than forcing it all through one line. Space Age especially rewards asking what NOT to bus over what to add.

Highest Priority: Iron Plates, Copper Plates, Steel, Electronic Circuits

Iron and Copper Plate Count and Growth

The first items on a main bus are iron and copper plates. Obvious reason: they're the foundation of nearly everything. As you chain together production, multiple lines want them _at the same time_. This is the perfect case for shared backbone over individual routing—the whole layout works out cleaner.

You don't need to go overboard from the start. I find 2 iron, 2 copper a comfortable entry point. Early-to-mid game? That's enough to organize assembly. Overshooting early just wastes belt space and muddies the overview. Honestly, room to expand later matters more.

The Factorio yellow belts at 15 items/sec, red at 30 items/sec. 48 stone furnaces fill a yellow line; 24 steel furnaces fill a yellow line (see https://wiki.factorio.com/tutorial:main_bus). Scale from there.

You'll usually spot iron shortage first, then copper chasing. Once circuits kick in, copper gets crushed hard. I thought 2 copper was safe until red-green science hit; then it tightened fast. Having it on the main line means one more belt solves it—cheap fix.

Steel: Why and When

Steel comes next—not consumed as heavily as iron or copper, but scattered across many spots. Trying to supply each location individually is tedious. A shared line saves huge routing overhead.

Timing: after iron and copper stabilize. Flow: iron → copper → steel → circuits works naturally. Pump steel too early and you're building furnaces for stuff you don't need yet. Get plates solid first, then steel as secondary.

The win here is demand distribution. If one huge factory eats all the steel, maybe dedicate a line. If it's "little bits everywhere," the shared bus really shines. I've tried local steel production in multiple spots—the furnace and routing overhead gets messy fast. Learned the hard way.

Running Finished Electronic Circuits

Electronic circuits fit the bus core nicely as a finished product. The big point: you're better off shipping completed circuits than shipping components and assembling at the destination.

Circuits take 1 iron plate + 3 copper wires. The ratio is about 3 copper wire → 2 circuits. If you try to assemble locally everywhere, each branch needs iron, copper, and wire—a routing nightmare. Just ship finished circuits and life gets simple: each branch takes one circuit line, no balancing raw inputs. Compare this to "make them on-site everywhere"—you're duplicating copper-wire assembly, fragmenting your copper plate consumption, and making the whole thing fragile.

I spent time during green-science making circuits at every location. Copper wire would vanish from one assembly point; somewhere else's iron would starve. Switching to one dedicated circuit block upstream, then running finished circuits as a single bus line cut the chaos completely. You track iron and copper consumption at one source, not scattered everywhere.

Later on, a huge dedicated circuit factory is strong too. But thinking of the main bus role, running finished circuits as one line is the cleanest, most stable approach: plates → shared → circuits assembled centrally → 1 finished line. Now the bus is a real production backbone, not just a materials rack.

Situational: Plastic, Sulfur, Batteries, Gears

These three (plastic, sulfur, batteries) are mid-game additions, not early stars. Since recipes and fluid/output specs directly impact how you run them, use the Factorio Wiki for numbers and line examples (Plastic bar: https://wiki.factorio.com/Plastic_bar, Sulfur: https://wiki.factorio.com/Sulfur, Battery: https://wiki.factorio.com/Battery). If demand clusters, dedicated lines. If it spreads, bus-feeding works. Judge as needed.

Gears: "Thin and Wide" or Local Bulk|http://www.thothchildren.com/chapter/5b6b06d12787593b86358c3d

Gears confuse people a lot. They're used everywhere, so they look like bus material. In the "I'm expanding belts and inserters constantly" phase, yeah, you want them in lots of places. So feeding one gear line is a reasonable early move if you're thinly spreading them.

The catch: Turning plates into gears inflates the transport volume. Shipping the plate and making gears _where you use them_ often keeps the trunk thinner. Especially for "this one spot needs tons of gears for a while" scenarios, running gears long-distance loses value.

I've tested this repeatedly. On-site gears usually look and feel cleaner. During co-op mining expansion, we made gears on-site near the mining rigs and belt setups—suddenly the main line only needed plates. Gear routing was local, the bus was lighter, and "why's this belt here?" confusion vanished.

The Factorio Wiki's on-site production concept|https://wiki.factorio.com/User:Fried_biter/workspace2 is handy when thinking about gears. The real question: Wide thin spread or dense local spiking? Judge by that, not by "gears are used a lot."

User:Fried biter/workspace2

wiki.factorio.com

Decision Flowchart: Bus vs. On-Site

The axis is demand scatter, not precise ratio math. I usually check in this order:

1. Look at consumption points: count and distance

Many sites far apart wanting the same stuff? Bus it. One or two nearby spots? On-site or dedicated.

1. Check peak demand per stream

Heavy per-line consumption means dedicated or on-site beats sharing. Oil products scatter here; gears often spike locally.

1. Does local stockpile help?

If expansion or construction waves hit one zone, making materials right there beats running empty between bursts. Gears feel this—plastic and sulfur often run smoother as "feed and cut as needed."

1. Belt width headroom?

Plates, steel, circuits already thick? Adding more items leans toward dedicated or off-site. Spare room? Feeding one more thing simplifies design.

Laying it out:

Many spread-out consumers → Bus candidate Few nearby consumers → On-site candidate Then: Heavy per-line → Dedicated, Light per-line → Bus, Bursty/local → On-site, Bus at capacity → On-site or off-site.

Plastic, sulfur, batteries: "scatter demand = bus, clump demand = local" is roughly right. Gears: "broad but thin = maybe bus, thick spikes = local." Don't rely on the name—think about _where and how_ it gets eaten.

Skip the Bus: Copper Wire and High-Consumption On-Site Products

Why Copper Wire Doesn't Go on the Bus

Copper wire is the classic newcomer temptation. Circuits use it, so it "should" be shared, right? I thought the same once. But transport efficiency beats convenience. One copper plate becomes two copper wires—you've intentionally made the cargo fatter for long distance. Main bus runs side-by-side materials, so a "doubles in transit" item clogs neighbors.

Yellow belts = 15/sec, red belts = 30/sec. Stuffing a material that bloats mid-route _will_ clog. Worse, copper wire isn't something you stockpile—circuits chew it up right next to where it's made.

In practice: carry plates, make wire right before assembly. Then the trunk runs plates, circuits eat wire locally, and you save belt count. I tried routing one copper-wire line once—instantly the circuit area sucked it dry and everything past it seized up. Wires only got there once I moved the assembly area (circuits + red circuits) near the bus start, made wires on-site, and fed plates. Flow normalized immediately.

The Factorio Wiki on this|https://wiki.factorio.com/User:Fried_biter/workspace2 points out: copper wire shouldn't ride the main bus. Heavy consumption + transport bloat = dedicated local production. "But it's used everywhere!" actually means "it's too hungry to bus efficiently."

On-Site Design Thinking

This is where on-site production shines. It's not rocket science: make what you need where you need it.

Example: circuit assembly line. Bus brings iron and copper plates. Right alongside, you make copper wires. Instant feed to circuits. Main trunk carries just plates; no distance-transport bloat. You cut transport count, rebalancing pain drops, and adding to the area stays local.

The sneaky big win: demand shocks stay local. If copper wires rode the bus and one area tripled circuits, you'd ripple upstream—re-split at branch, add lines, touch downst—the whole trunk gets touched. On-site, that zone fixes itself; your co-player's work stays untouched. Super valuable in multiplayer.

I often slot circuits and red circuits near the bus _start_. Short, thick copper-plate supply, make wires there, ship finished circuits. Copper wire never enters the main line—cleaner reading, no bloat, everything tighter.

Other Non-Recommended Examples

Copper wire isn't unique. Heavy intermediate products obey the same math: is there value shipping distance from origin to consumer?

Typical candidates: stuff that explodes in volume when processed (copper wire's cousins) and half-finished goods made where they're consumed immediately. Jam these onto a shared trunk and one big customer drags the whole line. It _looks_ shared but really becomes private anyway. Better to work local or split dedicated from day one.

Gears lean this way if they spike (local factories need a burst). Circuits do too if one area dominates. Even "refined oil" derivative stockpiles may hit local clusters—put production next to the consumer.

The core principle: The bus serves light-everywhere demand, not "one monster eats it" demand. Copper wire and bloating intermediates are the lesson. Master that and beginner buses _stay stable_.

Calculating Belt Count: Work Backward from Transport Capacity

Belt Capacity and Furnace Targets

Smart belt count comes from math, not vibes. Key stat: yellow belts carry 15 items/sec, red belts carry 30 items/sec. Need X items/sec? Belt count follows. Yellow = yellow, or swap one yellow for red. Rough it feels better than "make the bus fatter and hope."

Furnaces scale the same way. Stone furnaces output 1 plate per 3.2 sec = 0.3125 plates/sec. So 15/sec (one yellow belt) needs 48 stone furnaces. Steel furnaces? 24 per yellow. You now know what you're building toward.

I spent early game saying "sure, furnaces" with no target. Thought I was outputting 2 iron lines; really doing 1.5. The bus wasn't thin—my upst supply was. Embarrassing but educational.

This framework kills mystery at expansion: want 2 iron lines? 96 stone furnaces ballpark. Switch yellow→red? You double throughput on the same footprint. Numbers beat guessing. The factorio-community guide on bus design|https://wiki.factorio.com/tutorial:main_bus roots all this in the same math.

Early-Game Minimum Setup

Iron 2 · Copper 2 · Steel 1 · Circuits 1 is a clean entry spread. Easy to resource, easy to track. Overshooting early just bloats builds; grow as you need it. Since you're making wires on-site (earlier point), this count holds up great.

Why this works: iron and copper are nearly universal. Even one finished-circuit line relies on heavy plate supply—the plates are the resource pinch, not the circuits. So plates over width early—better to run thick plates than split into skinny circuits + scattered copper wire. Overbuilding the latter leaves you furnace-light and confused.

Expansion is simple: as one item gets hungry, add one line. Red science hits—add iron. Green science—add copper. Soon you're upgrading yellow→red or adding lines. Each expansion, you touch that material, not the whole bus. I quit re-wiring the entire trunk the moment I thought "just add one line to what's bottlenecked."

4-Line Grouping and Underground Span

Planning includes _placement_. Standard: 4 lines per group, 2-tile gap between groups. Visually, (iron plate 2 + copper 2), gap, (steel 1 + circuits 1), gap, etc. Spacing stays ergonomic for underground routing and cross-design. Easy to read later. Easy to hand a co-op player.

Key: yellow underground belts span max 4 tiles between entrance and exit. The 2-tile gap is right in the sweet spot. You can cross between groups without stretching belt limits. Packing tighter or wider makes later splits painful.

I once crammed belts 1-wide gaps. Adding a second copper line later, underground lengths jumped out of range—clunky retro-fit. 4 lines + 2-gap groups mean adding line = add to group, or start a new group. Underground distances stay friendly. Upgrade yellow→red? Same footprint, double throughput.

Splitter Priority Saves Downstream Deprivation

Input/Output Priority Basics

Splitting well beats even supply. Rather than "share equally," use splitters to starve the right loser. The Factorio Wiki main bus tutorial|https://wiki.factorio.com/tutorial:main_bus pivots on this: "feed priority first." Skewed _works_; starved downst doesn't.

Output priority is usually your tool. Example: a branch pulls copper. Say "fill the main line first, extra goes to my side-branch." Downstream stays fed, your branch takes scraps. Without it? First split consumes greedily; the 3rd split starves.

I learned this the hard way: add assembly, everything runs hungry downstream. Swap downstream priority to "main line first"? Magically stable. Last line now _survives_ when tight.

Right-Side or Outer-Biased Withdrawal

Lock in a takeout rule and read your factory much easier. Standard: take from the right or take from the outside. Run the same side the whole way—later, you'll see "this column feeds rightward" instantly. Switching sides per split? Nightmare to debug.

Pair this with priority setting: make right side "fill first" on splits. Then your right-flank threads feed clean—don't have to balance left-center later. Same idea for "outer first"—if your 4-belt group uses the outside lanes, let those feed first. Center lanes stay full longer.

Example: 4 iron belts, assembly on the right. Splitters "feed right first." Right side bulges, spare goes central. Central stays topped. No re-balancer junk mid-trunk.

Eliminating Re-Balancers

Main bus bloats re-balancers when one split side always empties first. Solution: don't split that way. Pick a direction, lock priority to match that direction. Add filters if different items touch.

I cut re-balancers massively when I stopped "re-balancing" and started "plan the split right from day one." Right-side takeout + right-side priority? Stayed stable. Adding a second assembly spot? Still right-feed. Never needed a re-balancer because downstream didn't starve.

Common Mistakes and Fixes

Packing Width Too Tight

Biggest newbie trap: cram the bus narrow early on. Few items early, so "should be enough" logic. Reality: mid-game hits and you're jammed. No room to slip a new line in, underground can't bridge crossings, re-routing costs grow fast. I hit this a bunch.

Fix: leave 2-tile gaps between groups. Even if you're clustering iron+copper as one 4-belt unit, gaps beyond let you slip new items without demolishing. Add a line = add to group, or place a new group in the gap. Not "squeeze 1 belt into a packed zone."

Can't fit new supply? Add groups, not lines within groups. Adding copper as a 5th belt squeezed into the iron zone invites chaos. Add it as a second copper group to the right, split clean. Reads better, expands nicer.

Slack space looks wasteful early. Mid-game when you're adding lines every session, it saves hours of re-work. Plan for it from the start.

Copper Wire Bus → Removal Walkthrough

Second classic fail: copper wire on the bus. Seems helpful; actually balloons width for little gain. Once you've locked wires on a trunk, the circuit zone sucks them up and everything past starves.

How to fix: move on-site production of wires. Plant circuits near the bus start. Copper plates come in short and thick. Make wires right there, feed circuits. Done—copper wire never left that zone.

Compounding error: circuits eating raw iron+copper directly from many points. Circuit material (iron 1 + copper 3 per circuit) hits multiple lines if you make them scattered. Consolidate. One circuit factory, one iron-copper draw, one circuit-finished output.

I tried scattered on-site circuits early—rampant, chaotic. Centralized block, one iron tap, one copper tap, one circuit line out? Stable. No question where the shortage hit. Now I test: are my late-game stalls from "not enough circuits" or "iron/copper spread too thin?" Centralized circuits always made that clear.

Flip from bus copper-wire to on-site: big stability jump. Multiplayer? Your co-player's problems stop leaking into your area via shared wire supply. Sanity win.

One-Side vs. Two-Side Expansion

Layout-wise, people debate: feed one side or both? Both look efficient; both behave very differently. One-side is simpler; two-side wastes real estate _and_ complicates reads unless you lock it down hard.

Easiest balance: symmetric trunk, one-sided takeout. Bus stretches both left and right evenly (clear architecture). But _take_ from right only (locked rule). Fewer ground crossings, cleaner splits, co-op doesn't accidentally tap left and ruin balance.

Two-side only works if you're truly symmetric—left has iron plate ×2, right has iron plate ×2, same order everywhere. Mix it up ("left is iron, right is copper") and you've lost all overview. One of you pulls left, another pulls right, suddenly items are scattered and nobody knows why.

Stick to: symmetric layout, asymmetric takeout. Or: one-side layout entirely. Either beats mixed.

Leveling Up: When to Graduate Off the Bus (Trains & Robots)

Warning Signs of Bus Limits

The main bus is amazing early-mid, then it hits a ceiling. Not because it's weak—because doing everything through one line stops scaling. The pain isn't "not enough belts to carry"; it's "the trunk is too crowded to read."

Clear red flags:

• Downstream starving constantly. Not occasional; persistent. Means supply can't reach through the network.
• Re-balancers multiplying. Adding devices to "

Summary and Next Actions

Decision Flow Recap

When in doubt, start by thinking only about iron plates, copper plates, steel, and green circuits as the main players -- that's the most stable design. Locking these in first means you won't need to rework the entire bus every time you expand. On the other hand, petroleum products and gears are best decided not by "is it correct to bus this" but by whether demand is scattered or concentrated -- that's about the right granularity. Copper wire should stay off the bus -- you can commit to that decision.

I was also tempted at first to line up everything that seemed necessary on the trunk. But what actually stabilized best was keeping bused materials slim and sharing green circuits as a finished product. This is quietly important. Think of the bus not as a highway for everything but as a trunk for items you want to share across multiple blocks for a long time, and decisions become much easier.

Checklist

• Remove copper wire from the bus; consolidate green circuits into a dedicated zone
• Add priority settings to branch splitters and check whether downstream starvation occurs
• Consider busing petroleum products and gears only when consumption points are scattered

Just running through these four steps makes your next login startup much smoother. Once you get lines quietly humming along, the factory's overall visibility improves dramatically too.