Try unsubscribing and subscribing again, the "small rural highway" was part of the Network Extension Mod which i removed and replaced with Mass Transit Road 7 Months ago.

@Sidai I already have it friend, "You already have Cities: Skylines - Mass Transit in your Steam library"

@Francisco Pizzaro: yes thats why Mass Transit DLC is listed as required

Error " Small Rural Highway is possibly DLC or mod content."