The right-hand side of a street is determined:
– in streets perpendicular or oblique to the course of the Seine, by the right-hand side of the passer-by walking away from the river;
– in streets parallel to the course of the Seine, by the right-hand side of the passer-by walking in the direction of the course of the river.
In the islands, the great channel of the river flowing to the north alone determines the position of the streets.