Roads and railroads (Civ4)

Roads and railroads allow units to move longer distances within a turn by reducing the movement costs of terrain.

When a unit is within hostile cultural borders, roads and railroads have no effect, unless the unit has the Commando promotion. When the civilization has an open border's aggreement allowing their units right of passage they may freely take advantage of roads and railroads though.

Roads

Back to the Tile improvements in Civ4

Road
Introduced in Civilization IV
Requires	The Wheel
Worker Turns to Build	2 turns
Other effects
Movement costs 1/2 movement points Movement costs 1/3 movement points with Engineering Movement costs 1 movement point if crossing River until discovery of Construction

Roads can be built after discovering The Wheel. With roads, all spaces cost 1/2 movement points (MP) to enter from other road tiles. After discovering Engineering, the cost goes down to 1/3 MP. In practice this means that a unit with just one movement point can move three tiles using roads. Similarly, units with two movement points can move six tiles.

Railroads

Back to the Tile improvements in Civ4

Railroad
Introduced in Civilization IV
Requires	Railroad
Worker Turns to Build	3 turns
Other effects
Movement costs 1/10 movement points +1 to Lumbermill, Mine, and Quarry

To build railroads, the civilization first needs to discover the Railroad technology and have an access to Coal and Iron. Railroads are similar to roads but they reduce the number of movement points needed to enter a tile from another railroad tile to 1/10 MP.

Railroad also give a bonus of 1 to tiles with a mine, a lumbermill or a quarry.