Learn Hardcore Indonesian: Rambu itu melarang putar balik di depan terowongan. - That sign forbids a U-turn in front of the tunnel.

Rambu is primarily used for traffic/road signs or official signage that regulates behavior, especially on roads. You’ll often see rambu lalu lintas (traffic sign).

tanda = sign/mark/signal in a very general sense (a sign of rain, a sign on a wall, a symbol).
papan = a physical board/plank; papan nama is a nameboard/placard.
So in traffic contexts, rambu is the natural choice. Saying rambu itu means that specific sign.

What does itu do here? Does rambu itu mean “that sign” or “the sign”?

Itu is a demonstrative meaning “that,” but it also functions like a definite article (“the”) when referring to a specific, known item.

rambu itu = that/the specific sign (already known from context).
Without itu, rambu would sound generic (“a sign”/“signs” in general).
A more formal alternative is rambu tersebut (“the aforementioned sign”).
ini would mean “this” (near the speaker): rambu ini.

Why is the verb melarang used, and what’s the base form?

The root is larang (forbid). The prefix meN- turns it into an active transitive verb: melarang (“to forbid/prohibit”).

Pattern: meN- + larang → melarang (the N assimilates to “l” giving “mel-”).
You can compare the passive form: dilarang (“is/are prohibited”).

Do I need to add untuk after melarang, as in “melarang untuk …”?

Usually, no. With an activity verb as the object, you just say melarang + verb:

Natural: melarang merokok, melarang parkir, melarang putar balik.
melarang untuk + verb is common in speech but often considered redundant.
Use untuk when you have a person as the object: melarang saya untuk merokok (“forbid me to smoke”).

Is putar balik a verb or a noun here?

It’s a verb phrase used as a nominalized activity (a “verbal noun”) functioning as the object of melarang. Indonesian often uses bare verb phrases this way: melarang putar balik, melarang parkir. On road signs, putar balik is a fixed collocation meaning “to make a U-turn.”

What’s the nuance difference between putar balik, balik arah, putar arah, berbalik, and memutar balik?

putar balik: make a U-turn (road context; very common on signs).
balik arah: turn around/change to the opposite direction (slightly broader, often in news reports).
putar arah: similar to balik arah; can be used in traffic reports.
berbalik: to turn around (intransitive, not specifically a driving U-turn).
memutar balik (sesuatu): to turn something back (causative), less used for a driver’s own U-turn.

Could I instead say Dilarang putar balik di depan terowongan?

Yes, and that’s the most sign-like phrasing.

Rambu itu melarang … = “That sign forbids …” (descriptive sentence about the sign).
Dilarang putar balik … = impersonal passive: “U-turns are prohibited …” / “No U-turn …” (exactly how signs sound).

In this sentence, does di depan terowongan describe where the U-turn is banned, or where the sign is located?

As written, it’s most naturally read as modifying the action: the U-turn is prohibited in front of the tunnel. However, Indonesian allows some ambiguity. To be explicit:

If you mean the sign’s location: Rambu di depan terowongan itu melarang putar balik.
If you mean the place of the U-turn: Rambu itu melarang putar balik di depan terowongan (or add clarity: melarang melakukan putar balik di depan terowongan).

Can I move the place phrase earlier in the sentence?

Yes, fronting is possible for emphasis or context-setting:

Di depan terowongan, rambu itu melarang putar balik.
This is grammatical, though the neutral order typically keeps location at the end. If you want to clearly attach the location to the sign, use: Rambu di depan terowongan itu …

Why use di and not pada with depan?

For physical location, di is standard: di depan, di belakang, di samping. Pada is used for more abstract relations (time, recipients, in formal style), not with depan for place.

What exactly is terowongan? Is terowong also used?

Terowongan means “tunnel” in Indonesian; the suffix -an forms the noun. Terowong is more common in Malay; in Indonesian, terowongan is the standard form.

Is there a difference between dilarang and tidak boleh?

Both communicate prohibition, but:

dilarang is stronger/formal and standard on signs/laws: Dilarang putar balik.
tidak boleh means “not allowed” and is more conversational: Tidak boleh putar balik. On official signage, dilarang is preferred.

Should I say melarang melakukan putar balik instead of melarang putar balik?

Usually no. Melarang putar balik is concise and natural. Adding melakukan (“to do/carry out”) can sound wordy or legalistic unless you need extra formality or clarity. Keep it simple on most occasions.

Could I use di hadapan instead of di depan?

Yes, di hadapan also means “in front of,” but it’s more formal/literary. In everyday speech and traffic contexts, di depan is the default.