[Hithredin]

This medieval example sounds like an easy shortcut though.

At part of Europe, roads were always maintened. Maybe with more local that country-wide focus sometimes. The feudalism may not caused by road system efficiency. Good roads on a empire splitted by succession are still no match to fast manoeuvrable drakkar raiders.

Local power and defence is needed... leading to another important parameter. Size of empires is proportional to time of travel and relative defensive strength of the remote area.

[imbnwa]

> Good roads on a empire splitted by succession are still no match to fast manoeuvrable drakkar raiders.

That's the issue though, dragons had gone extinct in Westeros 150 years before the series begins its story