The street signs in Mainz are a specialty of the city. There are blue and red road signs, with roads with blue signs running parallel to the Rhine and red ones perpendicular to it. The house numbers increase in the direction of the Rhine (i.e. larger numbers on the Rhine) and in the direction of the river. The odd numbers are on the left in ascending direction. There are also white signs with black letters, these streets have no clear direction parallel or perpendicular to the Rhine.