This is the 9849th most frequent Russian word.
автобусах
"Автобусах" means "buses" (prepositional plural form).
Here, 'автобусах' is used in the prepositional case, indicating the location where the action of reading occurs.
Я часто читаю книги в автобусах.
I often read books on buses.
In this sentence, 'автобусах' is in the prepositional case, used to specify which buses are being talked about.
В автобусах города стало больше мест.
There are now more seats on the city's buses.
Here, 'автобусах' is also in the prepositional case, as it indicates the topic of discussion, specifying the scope of the improvements.