Factorio Main Bus: What to Transport and Priority Order

The tricky part of main bus design is that while it looks easy to carry everything, you'll quickly bottleneck on copper wire and circuit boards. This guide uses Factorio vanilla v2.0 as a baseline and breaks down what to put on your main bus—and in what order—across four priority tiers, from essential to not recommended. The approach remains solid even as Space Age expands your factory's scope.

I remember hitting this myself right after red-green science packs. Two copper plates dried up in a heartbeat, and I thought, "Green circuit production is thirsty—way more than I expected." That's when I shifted to a setup with yellow belts at 15/s, red belts at 30/s, running 48 stone furnaces to feed one yellow line of iron plates and 24 steel furnaces for one yellow line of steel. I started with two lines each of iron and copper, made copper wire on-site, and moved completed electronic circuits onto a single bus line instead of raw materials. The whole factory stabilised noticeably.

So the core principle is simple: don't throw everything onto the bus from day one. Instead, stock your plate materials thickly and split the expanding intermediate products by their role—bus line, on-site production, or dedicated line. Let's walk through how to judge copper wire, gears, and electronic circuits across these three categories, with practical flows that fit real factory builds.

Factorio Main Bus: What to Carry and Priority Order—The Verdict

The Four-Tier Judgment Framework

When you're unsure what belongs on your main bus, sort it by four questions: "Does multiple production lines use this widely?" "Is the finished product thinner to carry than its materials?" "Does demand cluster in one spot?" "Would making it on-site feel more natural?" Breaking decisions this way saves endless second-guessing. I made the mistake of blurring these lines, kept adding materials, and ended up with a bus that was impossibly wide and unwieldy. Truth is, splitting between "shared staples" and "local sides" keeps your factory more stable than trying to centralise everything.

Here's the vanilla v2.0 verdict upfront:

Never put copper wire on your main bus—this is crucial. One copper plate becomes two copper wires, so you're basically fattening your transport for the same job. The electronic circuit area usually chokes right there, and I once tried flowing copper wire only to need more belt lanes with no practical benefit. I pulled it out and switched to local production.

Electronic circuits, though, have real value as finished products on the bus. You can pull iron and copper wire on-site and assemble there, but the demand is so heavy that each local production bubble eats into plate availability. An electronic circuit takes 1 iron plate and 3 copper wires, so even a single circuit line sucks a lot of copper. Consolidating circuit production into one area and pushing finished circuits down the line keeps your overall layout readable.

Gears sit in a grey zone. They're used everywhere, which superficially sounds like a bus candidate, but they're also trivial to craft from plates and often sit next to their point of use. Beginners usually fare better keeping gears local. Stick them on the bus only when multiple lines in the same area continuously chew through gears together.

Petroleum derivatives—plastic, sulphur, batteries—live or die by whether you partition the oil processing area. If multiple lines spread across your factory need them, the bus works well. If you cluster your chemical plants into one self-contained zone feeding one region, that's equally solid. The deciding factor is: do users spread out, or bunch together?

Starter Template

A friendly opening shape is the 4-belt group + 2-tile spacing pattern, with top-priority materials layered upstream. This layout plays nicely with underground belts and crossing tricks. You can scan it later and instantly know what flows where. The Factorio Wiki's Tutorial:Main bus covers the standard template well.

My go-to opening:

1. Iron plates (2 belts)
2. Copper plates (2 belts)
3. Steel (1 belt)
4. Electronic circuits (1 belt)

This order scales smoothly from early to mid-game. Starting with just iron and copper at 2 each, adding steel when you first need it, then electronic circuits next—that's the softest path. Dumping red circuits, plastic, and everything else onto the layout upfront bloats it before you use any of it.

Steel needs 2+ belts later on, but one suffices to start. Steel furnaces (hardened) peak at 24 units to fill a yellow belt. It lags plate production naturally and catches up easily. Electronic circuits, though, should become a dedicated line early once you see demand. That switch makes linking to red and blue circuits much smoother.

Red and blue circuits are the next step: add one belt each in a fresh group. But skip it if demand clusters; if modules and late-game items concentrate in one zone, keeping production local is neater.

Tutorial:Main bus

wiki.factorio.com

Version Scope and Caution

This priority ranking is for Factorio vanilla v2.0 series—a stable build like 2.0.73 is confirmed. The core logic doesn't shift much, but the guidance assumes pushing to late-game rocket production without undue strain.

For Space Age: be aware that DLC and mod specs and design best practices can diverge. Any specifics about interplanetary transport numbers or mod-specific mechanics should cite the official mod/DLC page (reference: Hoo's adoption guide https://note.com/hoo3863/n/n3de93e1891e7).

The same applies to vanilla: mid-to-large factories outgrow a single main bus. Steel mass production, mega circuit lines, and petroleum chains all benefit from dedicated lines or off-site zones. Further ahead, robot logistics and train networks naturally slot in. I love train grids, and misreading the handoff point is genuinely punishing. The main bus is strong, but it's not a one-size-forever solution.

So: aim for iron, copper, steel, and finished circuits as your core, add red circuits if demand spreads, and branch bigger items into dedicated lines. That holds up in vanilla v2.0 and scales decently into broader Space Age setups.

Background: The Main Bus Isn't a Catch-All Highway

Purpose and Scope

A main bus is a logistics strategy: stream primary materials in one direction and branch them where needed. The payoff isn't perfect transport—it's keeping your factory readable and easier to expand later. Prevents spaghetti. That edge is biggest in early-to-mid growth phases.

But the comparison to roads can mislead. The main bus isn't "a highway that carries anything"; it's the backbone for materials your whole factory lightly shares. Iron, copper, steel, finished circuits—widely consumed goods—suit it perfectly. Copper wire, which explodes in volume, clogs this backbone if you try.

The Factorio Wiki's Tutorial:Main bus treats the main bus as precisely this: a collector for primary resources. I started thinking "more materials = better organisation" and learned the hard way that it just fattens your footprint. Once a bus is locked in, retrofitting width is brutally awkward. And sprawling takes space, so oversizing early robs you of flexibility later.

This truth crystallises when circuits and oil derivatives scale up. A shared bus works magic for even-demand goods; it crumbles under specialised or local-heavy consumption. Readability and expandability matter more than gathering everything. Misunderstand that, and you'll bloat the bus for no gain.

Late-Game Alternatives

Once your factory swells past mid-game, a single main bus strains: you add materials, but bus width is your only dial. When big lines need dedicated production or far-flung mines must feed you, shoe-horning it all into one belt runs out of steam.

The move: keep the main bus running your factory's core, but hand off upline supply and mass transport to something else. Trains and robots do this work. Trains excel at long-haul plate delivery; robots handle fine-grained top-ups and connection shortcuts. The shift isn't because buses fail—it's because narrowing the bus's job keeps it powerful.

I've been in your shoes: I added rows of assembly machines to one side, the bus was already locked, and I spent hours trying to squeeze extra lanes where none fit. Parking a train station alongside and running bulk supply off-rail was faster. Bring iron and copper by rail, drop it locally, and feed short buses from there. Your factory transforms from one choked artery into layered systems.

Robots work similarly: use them for "many SKUs, low volume"—modules, constructs, miscellaneous refills. The main bus thrives with thick, steady flows; robots thrive with scattered, flexible demand.

Space Age Thinking

Space Age tilts the lever further: you don't push one mega-bus across planets. Each outpost gets a local main bus; transport between outposts goes by train or robot.

Even sources like Hoo's Space Age example reflect this: old main-bus-for-everything thinking breaks under expansion; local buses plus inter-site rail feels much tidier. I found the same: don't unify production across worlds; close gaps locally, connect worlds via trains. Especially true here—trying to run one bus spine through multiple planets, you hit trouble fast.

Really: in Space Age, the main bus is **the backbone of a single zone, not your whole megabase**. Local bus + train bridges = lean, extendable, survivable design. This, genuinely, matters.

Priority 1: Iron Plates, Copper Plates, Steel, Electronic Circuits

Iron and Copper Plate Count and Ramp-Up

Iron and copper are your first candidates for the main bus. Simple reason: they're the foundation. As you branch assembly lines sideways, lots of stations want them at once. Threads like this play nicer when shared from the start rather than traced individually to each consumer.

Count conservatively: 2 iron, 2 copper makes a solid launchpad. Early-to-mid pacing, this cushion is enough to organise your assembly sections. Oversizing upfront wastes belt real estate and muddies your overview. Space for later expansion beats false thickness now.

Factorio yellow belts carry 15 items/s, red belts 30 items/s. 48 stone furnaces output one yellow belt of plates. Steel furnaces peak at 24 units per yellow belt (check https://wiki.factorio.com/tutorial:main_bus).

Iron shortages surface first, then copper. Electric circuits multiply copper appetite—I thought 2 copper lines were ample until I fired up green packs and watched them vanish. Staging early pays: one more lane costs next-to-nothing if the trunk's ready.

Steel: Why and When

Steel sits next on the candidate list. You won't consume it like plates, but it's needed in splinters across many jobs. Routing fresh supply to each consumer every time grinds. One trunk line of steel saves wiring drama, and unlike plates, you can lean on lower throughput initially.

Sequence: iron → copper → steel → circuits. Nail the base metals first, stabilise them, then add steel once early lines are running. Steel is vital, but it's not what props up your factory's first breaths. Your plates are.

Steel's appeal lies in scattered demand. One massive line doesn't need it shared; dozens of small jobs do. Trying to hand-make steel locally explodes iron splits and furnace layout. I've tangoed with this pattern and regretted it. On-trunk steel simplifies mid-game sprawl immensely.

Electronic Circuits as Finished Goods

Electronic circuits belong on your bus as completed units, not raw materials. Here's why: running the finished product is steadier than distributing components.

A circuit needs 1 iron + 3 copper wire. The copper wire to circuit ratio is 3:2. Building on-site everywhere means each branch needs iron, copper, and copper wire—a tangle. Pushing circuits finished cuts this to "grab one circuit line"; iron-copper balance becomes invisible downline.

I used to sprite-build circuits at each consumer point mid-game. The copper wire consumption would spike somewhere, starving copper plate elsewhere, and my red-circuit and military lines would stutter. The instant I segregated circuit assembly into one zone and ran finished goods as a single line, the local stalls vanished. Tracing consumption became obvious.

I know many people run massive circuit farms later and pipe finished goods separately—totally valid. But within a main-bus strategy, complete circuits as a single trunk line is clearest and least likely to collapse. Foundation plates, add steel, then finished circuits. Your bus stops being a bin and starts being your factory's spine.

Situational: Plastic, Sulphur, Batteries, Gears

These three surface mid-game onward as expansion picks up. Since circuits, fluid specs, and output recipes shape your decisions, whenever citing numbers or designs, source the Factorio Wiki (Plastic bar: https://wiki.factorio.com/Plastic_bar, Sulphur: https://wiki.factorio.com/Sulfur, Battery: https://wiki.factorio.com/Battery). Clustered demand tips toward dedicated lines; scattered demand tips toward bus injection. Treat this as applied wisdom, not law.

Gears: Thin Spread or Local Glut?

Gears are genuinely tricky. They're everywhere, so they feel like a bus material. Honestly, if you're constantly expanding belts and miners and need gears in dribs across your layout, feeding one line is reasonable. But—and this is the catch—crafting gears inflates the physical volume you haul. Running ore as-is and assembling gears beside the user is often sleeker and beats a long gear belt.

Particularly when one corner gorges on gears—all your mining expansion at once—carving them locally beats ferrying finished gears from far away. I've tested this: on-site production looked tidy. Long-haul gears clogged the route for no gain.

I've tested it: gears on-site usually read cleaner and fit tighter than shipping them. When a mate and I expanded a mining outpost together, making gears right there meant we only needed iron from the trunk, and suddenly the core line felt loose. The opposite—pulling gears from afar—turned into "why is this belt here?" annoyances. Idle belts like that snowball into a hard-to-read factory.

The Factorio Wiki's 『User:Fried biter/workspace2』 covers on-site logic; gears are a poster child. High demand ≠ bus material. Ask instead: are consumers scattered (bus candidate) or lumped (on-site candidate)? That's the real lever.

User:Fried biter/workspace2

wiki.factorio.com

Bus vs. On-Site: Decision Flow

Consumption geography is your deciding axis. I typically check in this order:

1. Spread of consumers

Multiple far-apart clusters? Bus is worth considering. One spot or adjacent zones? On-site or a mini-line feels tighter.

1. Single-stream peak load

Heavy per-outlet? Dedicated line wins. Light per-outlet? Shared bus suits better. Petroleum byproducts vary here; gears often locally explode.

1. Local stockpiling

Construction waves want spare inventory. On-site production supplies that buffer. Gears fit this; plastic is more "flow and tap what you need."

1. Belt lane headroom

Your bus already packed with plates, steel, circuits? Adding items gets pricey in width. Skinny bus? One more line sharpens design.

Flowchart version: Many consumers, spread out? → Bus candidate Few consumers, together? → On-site candidate Further: Heavy single-stream consumption → Dedicated line Light multi-stream → Bus leaning Episodic local binges → On-site leaning Bus width tight → On-site or partition

Result: plastic, sulphur, batteries are "bus if scattered, dedicated if lumped." Gears are "local-first, bus only when many lines simultaneously pull steady." Compare to the material's consumption shape, not its name.

Not Recommended: Copper Wire and Heavy Intermediates

Why Copper Wire Fails

Copper wire lures every newcomer. It's in green and red circuits—surely one line saves routing hell. I thought so too. But here's the trap: one copper plate → two copper wires. You're inflating your cargo mid-route. Main buses run multiple materials side-by-side, so a cargo that doubles eats other lanes and clogs fast. Yellow belts cap at 15 items/s, red at 30 items/s. Double-volume cargo on one line? Bottleneck central.

Plus copper wire is almost pointless stockpiled. Circuits need 1 iron + 3 copper wires. Right next to your circuit machines, copper wire disappears fast. Copper plates carried long, wires made local—that's the sleek move. Forcing yourself to "add more lanes for copper wire" bloats your backbone and clouds your sightlines.

I tried it once: flowed copper wire down the bus, and red-circuit factories upstream vacuumed it instantly. The belt choked there, and everything downstream starved. Copper wire alone wasn't the villain—it was using a bus for 2-to-1 blowup material. Repositioned the circuit zone closer to the start, made wire on-site, and the pinch evaporated.

Factorio Wiki『User:Fried biter/workspace2』 also avoids copper wire on the bus. Heavy demand doesn't mean bus-it; heavy demand often means craft-it-local. You'll dodge a lot of grief remembering that inversion.

On-Site Design Philosophy

Enter on-site production: make what you need right beside the consumer. Copper wire and similar volume-expanding stuff pairs beautifully with this.

Example: your electronic circuit line needs plates and wire. Pull iron and copper down the bus; wire is made right there in the assembly zone and fed straight to circuits. Your trunk carries lean, high-value materials. Volume stays slim. When you rework one zone later, your trunk barely flinches.

The hidden win: consumption ripples stay local. Copper wire on the trunk means one zone's expansion tugs your whole backbone. Fixes ripple everywhere. On-site means change is confined; easier to patch, clearer to debug. Multiplayer amplifies this—your mate can expand a different area without your circuit upgrade derailing them.

I often slot circuit zones near the bus start. Copper runs short; carving wire on-site then consolidates copper demand and shrinks the trunk. Circuits sit where plates are thick; the local wire station absorbs all the copper-to-circuit alchemy. Readability soars.

Other Non-Recommended Examples

Copper wire is textbook, but any heavy intermediate that mass-consumes locally should be eyed for bypass. The lens: does this merit long-haul transport, or is it consumed locally?

Gears bundled with copper wire as local-heavy intermediates. Ore→gear→done right there? Keep it there. Giant blue-circuit farms? Cluster production, run finished goods by rail or as a isolated block. When demand is "mostly one zone, not spread," local beat or dedicated line beats shared trunk.

That copper wire episode taught me: the real villain wasn't the wire—it was trying to trunk two massive zone demands. Compact them, and you've solved the problem at source.

What chokes a bus: "many use it lightly" (solid bus material) vs. "one zone gorges on it" (dedicated or on-site). Copper wire and on-demand intermediates are your classroom examples. Master this split, and early-game bus design gets robust.

Belt Math: Reverse-Engineering from Throughput

Conveyor Speed and Furnace Math

Pick your main bus count from throughput math, not vibes. The baseline: yellow belts move 15 items/s, red belts 30 items/s. Once you know "I want X items/s of this material," required belt count emerges. Yellow-line full? Add a second yellow or swap to red. Clear arithmetic.

Furnaces work the same. Stone furnaces output one plate every 3.2 seconds, i.e., 0.3125 plates/s. To feed a yellow belt of 15 items/s, you need 48 stone furnaces. Steel furnaces (capped) need 24 units per yellow belt. I used to wing furnace counts and wondered why my plates fell short. Turns out I had 1.5 lines, not 2. Bus wasn't thin—source was undersized.

Once you crunch these numbers, scaling is trivial. Want 2 yellow lines of iron? 96 stone furnaces, or 48 steel furnaces. Yellow-to-red swap? Double throughput on the same footprint. Math makes "why's that slow?" answerable instead of mysterious. Factorio攻略局's Main Bus Design Guide anchors itself in belt speed and furnace counts—foundational stuff.

Starter Configuration

Lean on 2 iron, 2 copper, 1 steel, 1 finished circuits as your opening statement. Build thin, add only what slows you, ditch guesswork. Copper wire on-site as the anchor. This sketch holds surprisingly far and breaks rarely.

Why it works: iron and copper ground everything. Circuits multiplied copper hunger fast. Starting with fat plates and skinny midgame add-ons beats the reverse. Early isn't about ceiling-height buses; it's about padding your growth runway.

When adding more: grow one material at a time. Red sci will starve you for iron, then copper. Yellow→yellow (2→3) or yellow→red (same width, double flow) are your knobs. One stride sideways each pinch simplifies the flow. I ditched "rip out the bus every growth phase"; now each shortage is one lane, one swap. Vastly less rework.

Four-Belt Grouping and Underground Span

Plan the layout alongside count. Standard: 4-belt groups, 2-tile gaps between. Iron 2 + copper 2 = first group. Skip 2 tiles. Pile steel, circuits, etc. downstream.

This spacing pairs with yellow underground belts (max 4-tile void between ports). Crossing becomes natural; additions stay obvious; later you'll recall which line does what. Multiplayer appreciates column-clear intent.

Furnace output math + group discipline = no surprises. Yellow belt choked? Furnace count? Or just one fewer line? Math kills ambiguity. I've shifted from "buses feel slow" to "furnaces feeding 1.8 lines" and fixed it once. Huge morale swing.

Splitter Priority: Keep Your Tail Fed

Priority Tiers (Input/Output) 101

Don't split evenly; decide who gets first fill. Factorio Wiki's Main bus chapter pivots on this: feed your priority side first; leftovers scatter. Seems lopsided, but downstream stays alive. That's the goal.

Splitters have input and output priority. Output priority is your lever: "which exit fills first?" On bus splits, set the main spine to priority-fill. Feed the branch after the trunk has enough. This way, your backbone never starves, even during crunch.

Without priority? Upline eaters suck dry the first split, and downline dies. Been there. Every new assembly cluster and boom—tail line stalls. With priority set, at least the farthest consumer survives.

Filter + priority beats even distribution. Where multiple materials cluster, output priority safeguards the intended recipient. Sloppy parallel splitting kills.

Right-Side or Outer-Lane Consistency

Nail a pull rule early: always extract right, or always extract outside. Consistency means your brain knows where support exits and you don't trace the same confusion twice. Splitter placement and prioritisation align.

Right-side priority on right-side pulls = natural fill. Right lane stays dense; branch taps from an always-full pool. Fewer rebalancers needed. Takes-from-inside-outward feels cleaner than constant lane shifts.

The outer lane rules similarly: extract outer first, outer priority, and the central lanes stay undisturbed. Clean handoff, fewer logistics tangles. Four-belt groups respond well: take-outer-first means inner lanes sit quiet until overflow.

Instance: 4 iron belts, consumers on the right. Set right-lane priority, always pull from the right. Right lane stays plump; spillover is graceful, not strangled.

Rebalancer-Free Layout

Rebalancers sprawl when you split without direction. The antidote: decide pull direction, set priority to match, use filters to nail specifics. Done well, you scrap rebalancers almost entirely.

Example: multiple assembly blocks downright, eating the same input. Vanilla split-by-sequence starves the rear. Main-line priority + right-side extraction = all blocks stay fed, no magic lane-swapper needed.

Psychological win too: bus feels "held together" rather than "glued-together-with-duct-tape." That's setting-priority mattering.

Common Pitfalls and Fixes

Cramping: The Tightest Mistake

Most common bus fail: narrowing it too early. Upfront you feel safe, mid-game you're strangled. Widening later is agony.

The fix: leave 2-tile gaps between groups. Yellow underground spans 4 tiles max; 2-tile breathing room fits future lanes easily. I've crowded belts and regretted it badly.

When widening: do it in group units. Copper ran low? Add copper-group sideways, not one lane in the middle. Preserves rule, preserves readability, prevents cascade.

Whitespace is for future-you, who will bless past-you for foresight.

Copper Wire Ramp-Down

The other classic: copper wire on the trunk. It feels apt upfront, then it ruins balance.

Dismantling: move circuit zones to trunk start, run copper wire locally. Reroute ore slightly closer. This isn't a wholesale rebuild, just a reshuffle. Copper becomes material, not intermediate. Boom, stable.

The side effect: electric circuit and red circuit clustering near the top. Copper pulls drop near-end; far-end demand shrinks. Trunk lightens, runs smoother. Late-game sprawl is easier.

See『まるわかブログ』 Main bus example—copper local, plates thick—and you see the payoff.

One-Side vs. Two-Side Sprawl

Layout-wise: pull from one side only, or truly balanced?

One-side is simpler: rules stick, confusion dies. Two-side looks efficient until someone breaks the rule, and now you're chasing chaos.

My sweet spot: balanced trunk lines (both sides visible), but extract consistently from one side. Symmetric appearance, disciplined operation. Both worlds.

Multi-play amps this: one pull-rule prevents anarchic taps. "Take from the right" is universal enough even tired coworkers follow.

Graduation: When to Bail on the Bus

Bus Strain Signals

Buses are mighty early-mid, but midgame onward they hit a ceiling that's no longer material—it's footprint. Adding width costs space you don't have. You need replacement strategies.

Telltale signs:

• Constant downline starvation despite tweaks (not rare shortages—chronic).
• Rebalancers on rebalancers. You're gluing, not building.
• Belt and underground rewires mounting. You're servicing roads, not making goods.

Thresholds vary, but when a new production block demands main-bus rework, you've graduated. Stations become cheaper than rewiring.

I hit this when blue circuits perpetually choked despite rail-speed plates. A feeder station killed the pinch instantly.

Train Handoff

Don't discard buses; shrink their duty. Offload upstream supply, big consumption, long-haul items to rail.

Model: Smelters → Station → Factory entry → Local bus branches → Machines. Upstream is heavy, iron/copper/steel by train. Core factory shares thin, speedy bus lines. The shift is immediate relief.

Station discipline matters: waiting queues, signal placement, zero blocking to main line. I've learned it's not stations themselves—it's keeping stations out of the spine.

Transition cue: when expanding once means ripping the bus open, a station is cheaper. You'll feel it.

Robot Support

Robots aren't train replacements; they're tiny-load local couriers. Modules, science packs, construction refills—scattered low-volume—robots shine. Freight? No. Finesse? Yes.

Pairing: Belt for bulk, train for long-haul, robots for boutique. Clean separation.

Space Age Thinking (Again)

Planets wreck single-bus logic. Go **zone-local buses,