Does anyone know what the tech ability "Enables Bridges" on the Civilization Advances tab of the editor does? And how would it be used?

It enables bridges...

If a Civ has not researched a tech with the "enables bridges" option, it's units lose a full movement point when crossing a river, regardless if there are roads on each of the two tiles adjacent to the river. If they have researched a tech enabling bridges, then rivers have no effect on movement.

Thank you very much.