Infrastructure simulates the cost of transporting goods over land and creating the necessary foundation to support wide-scale industrialization.
To industrialize a state, it isn’t simply enough to build heavy industries there and have the pops available to work in them. The player also needs to ensure that said industries have enough infrastructure to support them.
It ties into several different mechanics such as market access, military logistics, migration, and others.
Infrastructure and market access on the state overview screen.
Infrastructure is provided and modified by numerous sources.
All states in the game have at least a little bit of infrastructure based on the technology level of the country that owns it and its state of incorporation (for example, colonies have lower infrastructure than incorporated states).
Geography is represented through state traits and it plays a significant role when it comes to infrastructure. State traits are bonuses and/or maluses given to a particular state representing particular geographical features, climate and so on. State traits have a variety of effects, but the most common ones are to either affect the production of a particular resource or to provide/modify infrastructure. For example, states with significant rivers get a large boost to infrastructure, making them excellent candidates for early industrialization.
There are short-term alternatives such as using authority on a road maintenance decree to ensure the populace don’t allow the roads to fall into disrepair or become unsafe, but such options will never be sufficient in themselves for large-scale industrialization.
Over the course of the game, the most crucial aspect of a nation’s infrastructure is the size of its railways network.
Railways is a building that produces transportation, an intangible good sold to pops, but they are also the nation’s main source of infrastructure. Railways must be able to find their way back to the market capital, or an exit port destined for the market capital, in order to be useful. In effect, this means that any railway can only provide infrastructure up to the amount of infrastructure provided by the best adjacent railway that connects it to the market capital.
This has a variety of costs involved in that infrastructure-providing railways need both pops to work them and access to goods like coal and engines. Of course, railways also grow more efficient over the course of the game with such inventions as diesel trains and electricity, requiring less levels of rail to support a certain number of buildings.
The infrastructure usage of a state is determined by which types of buildings exist in the state and on their levels. Generally, the more urban and specialized the building, the more infrastructure it will use per level. For example, chemical industries (a heavy industry building) will use several times more infrastructure than a rye farm building of the same level.
Note: Subsistence farms and urban centers do not use infrastructure. The former because its production is nearly all for domestic use and the latter because the infrastructure it provides cancel out the infrastructure it requires.
Infrastructure is represented by two distinct values that each state has: infrastructure and infrastructure usage. Both of these values determine the state’s market access. So long as the infrastructure in the state is greater than or equal to the infrastructure usage, everything is fine and the state maintains a market access of 100%, but if usage starts exceeding the available infrastructure, market access will be reduced by an amount proportional to how much of the usage is not being serviced. For example, if a state has an infrastructure of 45 with a usage of 90, its market access will only be 50%.
Low market access means that the state is unable to fully integrate its local market into the national market, which can lead to adverse price conditions from local over-or undersupply of goods. This imbalance goes in both directions. For example, if there is an iron mining state with a perfect market access, then the price of iron will be the same in all states. If the iron mining state’s market access is reduced, the market price of iron will go up due to undersupply while the local price of iron in the mining state will go down due to oversupply.
A good market access is essential for the production of complex goods. It is required both for sourcing specific input goods from another state in the national market (or via an import from a foreign nation) as well as for reaching a large enough population who can afford to buy them.