Learn Hardcore Indonesian: Rute alternatif disiapkan kalau cuaca berubah tiba-tiba. - An alternative route is prepared if the weather changes suddenly.

rute alternatif literally means “alternative route” in the sense of a planned detour or itinerary. It’s a loanword from English used in navigation, mapping, or travel‐planning contexts.
By contrast, jalan alternatif would mean “alternative street/road” – a specific physical road you could take instead of another. If you want to talk about the overall plan (sequence of roads), you use rute; if you’re naming a particular road, you use jalan.

How is the word disiapkan formed, and why is this passive structure used?

disiapkan is a passive verb formed with the prefix di- + root siap (“ready”) + suffix -kan, which together mean “to have something prepared” or “is prepared.”
Using the passive focuses on the action (“alternative routes are prepared”) rather than on who does it. It’s common in announcements or plans when the agent (the one doing the preparing) is either obvious, unimportant, or intentionally left unspecified.

There’s no subject in Rute alternatif disiapkan. Who is doing the preparing?

In Indonesian passive sentences, the agent (doer) is often omitted if it’s unknown, obvious, or irrelevant. Here it’s implied that whoever is responsible for traffic or route planning will prepare the detour. If you need to specify, you can add an agent with oleh:
• Rute alternatif disiapkan oleh petugas (“Alternative routes are prepared by the officers”).

What’s the difference between kalau and jika? Do they both mean “if”?

Yes, both mean “if.”
• kalau is more colloquial and widely used in spoken or informal writing.
• jika is more formal or literary.
You can generally swap them: Kalau cuaca berubah vs. Jika cuaca berubah.

Why is tiba-tiba repeated, and what does it mean here?

tiba-tiba is an adverb meaning “suddenly.” It’s formed by reduplication of the verb tiba (“to arrive”), a common way to create adverbs or indicate repetition/intensity in Indonesian (e.g., pelan-pelan “slowly,” sedikit-demi sedikit “little by little”).

Does Indonesian have tenses? How do I know if disiapkan refers to now or the future?

Indonesian verbs are not inflected for tense. Time is indicated by context or time adverbs. In this sentence, the conditional kalau cuaca berubah tiba-tiba implies a future scenario, so you understand that the preparation will happen when (or if) the weather unexpectedly changes.

Can I swap the order of the clauses? For example, start with Kalau cuaca berubah tiba-tiba?

Yes. Both are correct:
• Rute alternatif disiapkan kalau cuaca berubah tiba-tiba.
• Kalau cuaca berubah tiba-tiba, rute alternatif disiapkan.
Putting the “if” clause first simply shifts emphasis to the condition.

How would I say this in active voice, specifying the subject?

You can use an active verb with me-...-kan and add a subject. For example:
Kami menyiapkan rute alternatif kalau cuaca berubah tiba-tiba.
Here kami (“we”) is the subject, menyiapkan is the active form of “prepare,” and the rest remains the same.

Is rute alternatif singular or plural? If I mean several detours, do I need to change it?

Indonesian nouns are unmarked for number. rute alternatif can mean one or multiple routes. If you want to emphasize plurality, you can reduplicate: rute-rute alternatif (“alternative routes”), but usually context makes it clear.