Hola! Calzada y carretera son sinónimos. En Venezuela se le dice carretera. Para mi no hay diferencias porque cuando escribes y no quieres repetir la palabra carretera en un párrafo, simplemente utilizadas la palabra calzada. Espero haberte ayudado. Nos vemos :)

You probably meant "Carretera" and Calzada. Both are "the part where vehicles circulate". The difference is that we call Calzada to the part of the street is between two sidewalks while Carretera is for roads outside the city. In Spain the word Calzada is out of use and we usually call everything Carretera.

it's not carrebera, is "cabecera" Calzada, is like a main street In the middle of two sidewalks, and Cabecera is like a small city.