Roads generate Gold. Each building that is joined to the Town Center by Roads gives 10% extra Gold, the Building Bonus.
Gold is stored in Roads until collected. The maximum that can be stored depends on the storage capacity of the Roads. When the Gold reaches a certain threshold of the capacity, a tax collector will appear on the Road with a Gold icon above his head.
Upgrading your Roads will increase both the Gold produced and the storage capacity.
You can place a Gate on a Road to connect Walls on either side.
You can place traps on Roads.
Selecting a Road will highlight buildings connected to the Town Center by Roads in a green glow.
Caravans move along Roads and will drop any Gold on the Roads they have collected when an attack starts.
Roads also provide a health bonus to the Town Center depending on the amount of buildings connected to the Road.
During an attack, the Gold generated by the Roads is stored in the Town Center.
Road income is calculated as (number of roads) x (base income per road) x (100% + building bonus), and is then rounded down to the closest multiple of 40. Note that this counts the number of Roads, not the number of Roads connected to the Town Center. Connecting Roads to the Town Center is only required for the building bonus.