Si le métro s’arrête trop tôt, nous appelons un chauffeur de taxi.

Si means if.

It introduces a condition:

• Si le métro s’arrête trop tôt = If the metro stops too early

In French, si is the normal word for if in this kind of conditional sentence.

Because the verb here is s’arrêter, which means to stop.

There is an important difference:

• arrêter = to stop something / to arrest
• s’arrêter = to stop oneself / to come to a stop

So:

• Le chauffeur arrête la voiture. = The driver stops the car.
• La voiture s’arrête. = The car stops.

In your sentence, the metro is the thing that stops, so French uses s’arrêter.

The full form is se arrête, but French avoids two vowel sounds together here, so se becomes s’ before a vowel or silent h.

So:

• se arrête → s’arrête

This is called elision.

You will see this often:

• je aime → j’aime
• ne est pas → n’est pas
• se appelle → s’appelle

The circumflex in arrête is just part of the spelling of the verb form.

This is the present tense of s’arrêter for il/elle/on:

• je m’arrête
• tu t’arrêtes
• il/elle/on s’arrête
• nous nous arrêtons

The accent helps distinguish forms such as:

• j’arrête
• tu arrêtes
• il arrête

You do not need to translate the accent separately; it is simply part of the correct written form.

French often uses the present tense in both parts of a conditional sentence to express a habit, general rule, or usual reaction.

So this sentence means something like:

• If the metro stops too early, we call a taxi driver
• more naturally in English: If the metro stops too early, we call a taxi / we get a taxi

This sounds like a routine or standard response.

If you wanted a more specific future situation, French could say:

• Si le métro s’arrête trop tôt, nous appellerons un taxi.

That would mean:

• If the metro stops too early, we will call a taxi.

Usually, not directly in the si-clause.

Standard French does not normally say:

• Si le métro s’arrêtera trop tôt... ❌

Instead, French uses:

• si + present, then a present/future/imperative in the other clause

Examples:

• Si le métro s’arrête trop tôt, nous appelons un taxi.
• Si le métro s’arrête trop tôt, nous appellerons un taxi.
• Si le métro s’arrête trop tôt, appelle un taxi.

So the important rule is:

• after si meaning if, do not use the future tense

Trop tôt means too early.

• trop = too / excessively
• tôt = early

It comes after the verb because it modifies the action:

• s’arrête trop tôt = stops too early

This word order is normal in French.

Compare:

• Il arrive tôt. = He arrives early.
• Il arrive trop tôt. = He arrives too early.

French uses articles much more often than English.

So where English might sometimes say:

• Metro
• Subway

French usually says:

• le métro

Here le métro can mean:

• the metro system in general, or
• the metro in the situation being discussed

French normally prefers the article here.

Un means a or an.

So:

• un chauffeur de taxi = a taxi driver

The indefinite article is used because it is not a specific taxi driver already identified.

That said, in everyday French, people often say:

• appeler un taxi = to call a taxi

This is often more natural than appeler un chauffeur de taxi, depending on context.

So your sentence is grammatically correct, but appeler un taxi may sound more idiomatic in many real-life situations.

Both can mean we call.

• nous appelons = more formal, more careful, common in writing
• on appelle = very common in everyday spoken French

So in natural conversation, many speakers would say:

• Si le métro s’arrête trop tôt, on appelle un taxi.

That is often the most natural spoken version.

As written, it most naturally sounds like a habit, policy, or general reaction.

So it suggests:

• Whenever this happens, that is what we do.

If you want to talk about one specific future event, French often uses the future in the main clause:

• Si le métro s’arrête trop tôt, nous appellerons un taxi.

So the contrast is roughly:

• present + present = habit / general truth / usual reaction
• present + future = specific future possibility

A simple pronunciation guide is:

Si le métro s’arrête trop tôt, nous appelons un chauffeur de taxi.

Approximate pronunciation: see luh may-troh sah-ret troh toh, noo zah-puh-lohn uhn shoh-fur duh tak-see

A few useful notes:

• métro → the é sounds like ay
• s’arrête → sounds roughly like sah-ret
• tôt → long o sound
• nous appelons → the s in nous is normally silent, but it links before appelons, so you hear a z sound: noo-zappellons

Yes, that is the literal translation.

But in natural English, people are more likely to say:

• If the metro stops too early, we call a taxi.
• If the metro stops too early, we get a taxi.

Likewise, in French, appeler un taxi is often more idiomatic than appeler un chauffeur de taxi.

So the French grammar is fine, but the most natural everyday wording might be slightly different in both languages.