Transport Belt Systems - Factorio-Access/FactorioAccess GitHub Wiki

Transport Belt Systems

Prerequisite: This page covers advanced belt techniques. For belt fundamentals, read Transport Belt Basics first.

This page covers splitters and advanced belt techniques. For belt and underground belt fundamentals, see Transport Belt Basics.

Splitters

A splitter is a 2×1 machine with two belt inputs on its back side and two belt outputs on its front. Its function is determined automatically by which inputs and outputs are in use — no configuration is needed for basic splitting, merging, and balancing. Unused outputs hold items like a stopped belt end. An important property of splitters is that they preserve lanes: items on the left input lane go to the left output lane and vice versa.

Splitting — one input belt feeds two output belts, distributing items evenly between them. This sends one source to multiple destinations. Setting an output priority directs all items there first, overflowing to the other output only when full.

Merging — two input belts feed one output belt, combining their contents while preserving lanes. Setting an input priority drains that side first, drawing from the other only when space allows. This is cleaner than sideloading, which forces both lanes of one belt onto a single lane of another and halves throughput.

Balancing — two inputs and two outputs with no priority set. The splitter equalises flow across both inputs and both outputs, ensuring neither belt starves. For three or more parallel belts, placing a splitter between every neighbouring pair achieves basic balancing through overflow.

Lane balancing — a splitter alone does not mix lanes. To balance the two lanes of a single belt, split it into two belts with the splitter, then sideload both outputs onto a new belt at a safe merge junction. Each lane of the new belt ends up with half the total item count of the original, producing a lane-balanced result.

Belt compression — a fully compressed belt has no gaps. To compress a flowing belt, feed two partially filled belts into a splitter and sideload both outputs onto a third belt. If the combined input traffic is sufficient, the output belt will run fully compressed. Note this reduces total throughput unless the output belt is a faster tier.

Splitter priorities

Select a splitter and press SHIFT + LEFT ARROW or SHIFT + RIGHT ARROW to set input priority. Press the same direction again to restore equal distribution. Use CTRL + LEFT ARROW or CTRL + RIGHT ARROW for output priority.

Splitter filtering

A splitter can be configured to route one specific item type to a designated output, sending everything else to the other output. This is useful for sorting mixed belts or separating lane-mixed content. To set a filter, hold the target item in hand and press CTRL + LEFT BRACKET on the splitter, then set the filtered output direction with CTRL + LEFT ARROW or CTRL + RIGHT ARROW.

Note that if the filtered output is full, the other output backs up too, since filtered items have nowhere to go. This is different from priority mode, where one output backing up does not affect the other.

Load balancing

Load balancing is the practice of distributing a supply of items evenly across multiple consumers, or combining multiple supplies evenly into one stream. Without balancing, some machines may starve while others are oversupplied, reducing overall throughput even when the total supply is sufficient.

The basic tool for load balancing is the splitter. A single splitter between two parallel belts carrying the same item will equalise flow across both. For larger setups, chaining splitters between every neighbouring belt pair provides basic balancing — items overflow from saturated outputs to underused ones naturally. The Factorio community has developed many multi-splitter configurations for perfectly balanced networks at any scale, which are worth looking up if high-throughput balancing becomes a priority.

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