Chapter 5 ‐ Transport belts part 1 ‐ Segments, lanes, and other basics

Previous page: "Chapter 4 - Inserters part 1 - Inserter logic and burner inserters"

Transport belt

Transport belts are single-tile machines that can transport items automatically. They are flat conveyor belts that uniquely require no energy source and are actively running in one direction when placed. Belt units can face any of the four main directions. Multiple belt units placed end-to-end can form large belt segments that seamlessly connect. In the context of this guide, we will refer to one belt segment as one or more consecutive transport belt units that are added end-to-end in a straight line. An important feature about transport belts in Factorio is that they all have two lanes, meaning that two different items can travel side-by-side along a belt segment without interacting with each other.

Items on belts

Items on belts exist as non-stacking entities just like items on the floor and they can also be picked up by an engineer standing next to or on top of the belt (by holding the “F” key). Items on a belt will travel along the belt's direction until they stop either by reaching the end of their lane without falling onto the floor or by bumping into other items that are already stopped, hence forming queues along the belt’s two lanes. A belt unit can hold up to four items per lane. If a belt segment that has no empty spaces remaining on it, it is said to be compressed.

Items can be placed on and off of belts only via inserters, with the exception of mining drills being able to drop ores directly onto them. Inserters always place on the lane that is farther away from them, even if the nearer lane is empty. Drills always place on the lane that is nearer to them. Inserters can pick up from both lanes, but they prefer the nearer lane.

Systems with multiple belt segments

Transport belt segments can be arbitrarily long. Meanwhile, transport belts can form corners where they turn at right angles. By turning a corner multiple times, the belts can form loops on which items can go around infinitely. Normally, items never fall off the end of a belt segment. The exception is when a belt ends at the side of another belt, which allows the ending belt to pour onto the other belt, forming a sideloading junction. There are different types of sideloading junctions depending on the arrangements of belts. Belt segments and junctions can also be combined with underground belts and splitters to make complex belt systems. If an area has many belts going all over the place without any particular alignment, the popular term used among engineers to describe it is "belt spaghetti".

Belts with one or more item types on them

The basic option is to have one type of item per belt, such as a belt dedicated to carrying only coal. If you do this, everything becomes simple because you do not have to care about lanes or picking up wrong items. Every inserter taking from the belt is guaranteed to get only that type of item. On the other hand, having to build a separate belt for every item type means that your belts will take up a lot of space and you will need to craft lots of them.

A popular second option is to have two item types per belt, specifically by having one item type per lane. This is practical because you can use one belt to do the job of two belts. This means that you can craft fewer belts overall and you also use space more efficiently. For many cases you also eliminate the need for long handed inserters. The disadvantages of this option is having to be careful about lane usage. While straight belts and corners do not mix their lanes, any sideloading junction can cause lane mixing unless it is a safe merging junction. Furthermore, the restriction of inserters only being able to place on the further lane means that belt and inserter layouts need to be planned carefully to prevent lane mixing.

Carrying more than two types of items on a belt is possible but not popular. When you have more than two item types on a lane, due to lane mixing or otherwise, you create the risk of blocking the belt. This happens when the picked up items are removed from the belt but unused items stay and fill up the lanes so that all other items eventually get blocked. You can use careful belt system planning so that every item ends up at least somewhere else and the belt is not blocked, but this is hard to maintain indefinitely. The extreme version of this approach is called a "sushi belt" where a little bit of everything is on the belt and it is very carefully managed to prevent blocking.

Belt corners

A corner is formed automatically when you place a belt unit such that you have the end unit of one segment pointing at the start unit of another segment. This arrangement uniquely restructures the receiving belt unit: It becomes curved so that items go around corner while they preserve their lanes. The lanes on the corners run at different speeds such that items on both lanes go around the corner at the same time despite covering different distances. This does mean that one lane at the corner is moving much faster than the other. This temporary speed-up means that slow inserters at belt corners might fail at grabbing any items.

Belt sideloading junctions

As mentioned previously, items never fall off the end of a belt segment. The exception is when a belt ends at the side of another belt's middle section. This makes the ending belt pour onto the other belt from one side, hence the name sideloading. For the pouring belt, items on both lanes are emptied. For the receiving belt, all the items fill onto only the belt lane that is closer to the pouring belt. Since the contents of both pouring lanes are poured onto the same receiving lane, the lanes end up mixing. When the belt system is crowded, the items being poured wait for the items that were already on the belt before dropping. Due to this behavior, half of a belt being poured waits for its other half as two lanes get forced onto one, which effectively halves the overall carrying speed of the belt being sideloaded.

Safe merging belt junctions

If a belt unit is being sideloaded from both sides, it is said to be double sideloaded. If, additionally, the belt unit is at the start of its segment, meaning that there is no belt unit feeding into it from the back, then this is a special kind of junction that is said to merge safely. It is safe because you have the two pouring belts sideloading onto different lanes and no other belts from the back add to the lanes, meaning that the lanes certainly do not mix.

Transport line analyzer tool

This mod menu tool provides overviews for all the items currently on a transport belt, including individual lanes and parts of the belt that are upstream or downstream from the unit being analyzed. The analyzer also announces which lane is on which side of the belt, which helps with determining how you can build your sideloading junctions.

Select a belt unit and press "LEFT BRACKET" to open the interface. This will read the ID number assigned to the entire belt that this unit is a part of. Press "TAB" to switch between different information tabs. Use "W" "A" "S" "D" to navigate between the two lane options within the same tab.

Building tips for transport belts

• If you need a long and straight transport belt, you can stand on the belt start, rotate the belt item in hand to face the direction you want, and then enable build lock mode with CONTROL + B. The belt will be placed on every tile you step off from. While doing this, if you are not in Cursor Mode and you change your running direction, the belt will also rotate to match your new direction, although the corner belt unit might not be placed automatically.

• If you want to build a belt corner or sideloading junction, building in cursor mode makes it much easier to keep track of which unit is where on the ground. In version 0.4, we added belt junction information to the belt building preview as well.

• You can guarantee lanes not mixing on a belt if you used no sideloading onto it and be careful about where inserters deposit onto the belt.

• You can guarantee that items on a belt end up on a particular lane if you use sideloading. While the nearer lane is easy to pour onto directly, you can reach the further lane by using some inserters, which will place only onto the further lane.

• You can do sophisticated item management with belts when you use inserters and splitters and chests.

Next page: "Chapter 6 - Fluid handling part 1 - Fluid behavior and pipes"

See also: Chapter 10 - Transport belts part 2 - Underground belts and splitters