is it not also correct to say, "коли буде наступна маршрутка"?
Hmm... In Ukrainian it's a totally proper sentence, and also used pretty often, but yeah, I cannot find any other English sentence beside "When is the next bus" ("When will the next bus be" sounds wrong), so I guess this answer should be accepted.
"When will the next bus be," is not wrong at all and doesn't sound wrong either.
OK, thanks! I still think the first one is more common, if you just want to ask a person in some ticket office or at the bus stop.
Yup 'коли буде наступна маршрутка' should definitely be accepted
коли наступна автобус?
No, you didn't conjugate the adjective наступна. Since автобус is a feminine case, you need to conjugate adjective accordingly
Thanks for pointing that out. I missed that.