Roads on islands

[Diamondj]

Is there any point in building a road on an Island with only one city on it? Does it improve trade just by going to the port?

[Mouzafphaerre]

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Logically, it will increase the transport speed and capacity, so yes, more stuff will be shipped between your town and port in the same time. Technically, I don't know.
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[AngryAngelDD]

certainly not for sweboz or getai (?) etc.
their simple roads add nothing to law etc.
you only have the speed bonus for your units there. (if any, when roads are short like in Gawjam~Rugoz)

but for romans and hellenes (and others) for example level2-roads and up add 5% to law (so at Corsica and Sardinia)

[pseudocaesar]

Doesnt matter where they go, Roads as a "building" increase trade.