Why is "tren" singular in "estación de tren", but "autobuses" is plural in "estación de autobuses"?

Question

Why is "tren" singular in "estación de tren", but "autobuses" is plural in "estación de autobuses" (per the website Duolingo)?

Or is it also correct if I write "estación de trenes" or "estación de autobús"?

Answer 1

I don't know about Duolingo but according to the DRAE:

estación

4. f. Edificio o edificios en que están las oficinas y dependencias de una estación del ferrocarril o de autobús.

Notice that the DRAE employs the singular form in the above definition (just replace ferrocarril by train, they are synonymous)

You can use both singular and plural forms to designate the same building. A estación de tren is the same as a estación de trenes. And the same occurs with autobus/autobuses.

As pointed by other users, in small populations train stations usually has got a single line, just one train comes around, and due to Spain being a rural country for a long time that name remains.

As a side note, in great cities, the central train station (with multiple lines) is usually know by its proper name, like Atocha in Madrid or María Zambrano in Málaga, while bus stations have got not proper name or nobody uses it.

Answer 2

Both "estación de trenes" and "estación de autobús" are correct, it's just that "estación de tren" and "estación de autobuses" are more common than the alternatives (at least in Spain).

As for why, my wild guess is that no more than one train is usually stopped in smaller "estaciones de tren" at a given time, but even the smallest "estaciones de autobuses" frequently see multiple buses stopping at the same time (otherwise they would be mere bus stops). Again, this is just a wild guess.

Answer 3

No sé si puedo responder en español para ser más claro. Mi suposición es la siguente. En cada "estación de autobuses" paran varias líneas mientras que en una "estación de tren" a lo mucho pasan 2 trenes que vayan a distintos lugares.

Sin embargo, en Argentina, es mucho más frecuente usar "parada" (creo que uds. también usan la palabra "stop") acompañado de "colectivo/bondi/ómnibus/autobús" en singular. Así que no parece tener ninguna relación.