Sur l’autoroute, Paul n’aime ni accélérer trop vite ni doubler quand il pleut.

Sur l’autoroute means on the highway / on the motorway.

French often puts a place phrase at the beginning to set the scene. So the sentence starts by telling you the setting, and then says what Paul does not like to do there.

A more neutral order would be: Paul n’aime ni accélérer trop vite ni doubler sur l’autoroute quand il pleut.

But the original version emphasizes the highway first.

In French, general nouns often take an article where English might not. So French says sur l’autoroute literally on the motorway/highway, even when speaking generally.

This is very common:

• à l’école = at school
• à la maison = at home
• dans la voiture = in the car
• sur l’autoroute = on the highway

Ni ... ni means neither ... nor.

So:

• ni accélérer trop vite ni doubler means
• neither drive faster and faster / accelerate too much nor overtake

It links two things that Paul does not like doing.

Because ni ... ni works with the negative idea, so pas is not used here.

Compare:

• Paul n’aime pas accélérer trop vite.
  = Paul does not like accelerating too fast.

• Paul n’aime ni accélérer trop vite ni doubler.
  = Paul likes neither accelerating too fast nor overtaking.

So ni ... ni replaces the role that pas would normally play.

Because they come after aimer.

After verbs like aimer, adorer, détester, préférer, French often uses an infinitive:

• J’aime lire. = I like reading / I like to read.
• Il déteste attendre. = He hates waiting.
• Paul n’aime pas doubler. = Paul does not like overtaking.

So here:

• aimer accélérer
• aimer doubler

are both normal structures.

A learner might notice that, yes. Accélérer already means to accelerate / speed up, and trop vite means too fast.

So accélérer trop vite means something like:

• to accelerate too fast
• to speed up too quickly

It is not wrong or unnatural. Trop vite adds the idea that the increase in speed is excessive or too sudden.

Here doubler means to overtake / to pass another vehicle.

In road vocabulary, doubler is a common verb for passing a car, truck, etc.

Examples:

• Il double un camion. = He is overtaking a truck.
• On ne peut pas doubler ici. = You can’t pass here.

It does not mean to double in the mathematical sense here.

Yes, sometimes, but they are not always exactly the same in feel.

• doubler is very common in driving contexts and specifically suggests overtaking another vehicle
• dépasser can also mean to pass / overtake, but it is broader and can mean to go beyond, to exceed, or to pass by

In this sentence, doubler is very natural because the topic is driving on the highway.

Grammatically, because quand il pleut comes right after doubler, the most natural reading is:

• Paul doesn’t like accelerating too fast
• and he doesn’t like overtaking when it rains

So the rain phrase is most directly linked to doubler.

However, in real context, a listener might also understand that the whole situation is about driving in rainy conditions. If you wanted to make it clearly apply to both actions, French could say:

Quand il pleut, Paul n’aime ni accélérer trop vite ni doubler.

That version makes the rain condition cover the whole sentence more clearly.

In il pleut, the il is an impersonal subject. It does not refer to a person or thing.

English does the same with it:

• It is raining.
• It is cold.

French uses il in many weather expressions:

• il pleut = it’s raining
• il neige = it’s snowing
• il fait froid = it’s cold

So the il here is just required by French grammar.

Because ne becomes n’ before a vowel sound.

This is called elision.

So:

• ne aime becomes n’aime
• ne accélère would become n’accélère
• le autoroute becomes l’autoroute

French does this very often to avoid awkward vowel clashes.

A natural English translation would be something like:

• On the highway, Paul likes neither accelerating too fast nor overtaking when it’s raining.
• More naturally: On the highway, Paul doesn’t like speeding up too much or overtaking when it rains.
• Or: On the highway, Paul doesn’t like to accelerate too fast or overtake when it’s raining.

Even though ni ... ni literally matches neither ... nor, English often sounds more natural with doesn’t like ... or ....

The structure is:

• Sur l’autoroute = place phrase
• Paul = subject
• n’aime = verb
• ni accélérer trop vite ni doubler = two infinitives linked by ni ... ni
• quand il pleut = time/condition clause

So you can think of it as:

On the highway, Paul does not like neither X nor Y when it rains

More naturally in English: On the highway, Paul doesn’t like either X or Y when it rains / Paul likes neither X nor Y...

Here the two actions are:

• accélérer trop vite
• doubler