Quando il tassista ha visto la strada chiusa, ha preso una deviazione senza che io dicessi nulla.

Ha visto is passato prossimo, and it presents the seeing as a completed event: the taxi driver saw that the road was closed.

That fits the sentence well because the driver’s action sequence is:

1. he saw the road was closed,
2. then he took a detour.

If you used vedeva, it would sound more like an ongoing background situation, such as he was seeing / he could see, which is not the main idea here.

So:

• ha visto = a finished event
• vedeva = an ongoing or habitual background action

In this sentence, the completed event is the natural choice.

Because chiusa agrees with la strada, which is feminine singular.

• strada = road, feminine singular
• chiuso / chiusa / chiusi / chiuse = closed, with agreement

So:

• la strada chiusa = the closed road / the road closed off

This is normal adjective agreement in Italian.

In form, yes, it literally looks like the closed road, but in context it means something more like:

• the road was closed
• the road was blocked off
• the street was closed

After verbs like vedere, Italian often uses a structure like:

• ha visto la strada chiusa

This is similar to he saw the road closed or, more naturally in English, he saw that the road was closed.

So chiusa is describing the state of the road at the moment he saw it.

Ha preso is also passato prossimo, because taking the detour is another completed action in the story.

The sentence gives a sequence of completed events:

• ha visto = he saw
• ha preso = he took

Using the same tense for both actions keeps the narration clear and natural.

Also, prendere una deviazione is a common way to say to take a detour.

It means to take a detour.

Literally:

• prendere = to take
• una deviazione = a detour, deviation from the usual route

So ha preso una deviazione means the driver changed route because the normal road was unavailable.

This is a very natural expression in Italian.

Both are possible, but they are not structured the same way.

1. senza che io dicessi nulla

This means:

• without me saying anything

It uses a full clause with its own subject: io.

2. senza dire nulla

This means:

• without saying anything

This version does not explicitly state the subject. Usually, the understood subject is the same as the subject of the main clause.

In this sentence, the main subject is il tassista, so senza dire nulla could sound like without the taxi driver saying anything, not without me saying anything.

That is why senza che io dicessi nulla is especially useful here: it clearly shows that I am the one who did not say anything.

Because senza che normally requires the subjunctive in Italian.

So after senza che, you do not use the ordinary indicative forms like:

• dicevo
• ho detto
• dicevo

Instead, you use the subjunctive:

• senza che io dicessi nulla

This is a standard grammar rule.
Senza che introduces a subordinate clause expressing something that did not happen before or during the main action, and Italian uses the subjunctive in that kind of clause.

Dicessi is the imperfect subjunctive of dire.

Here is the logic:

• the main clause is in a past tense: ha preso
• after expressions like senza che, when the main clause is in the past, Italian often uses the imperfect subjunctive

So:

• senza che io dica nulla = present-time context
• senza che io dicessi nulla = past-time context

In your sentence, the whole event is narrated in the past, so dicessi is the correct choice.

Yes, it could be omitted, because Italian often leaves out subject pronouns when the verb ending already makes the subject clear.

So both are possible:

• senza che io dicessi nulla
• senza che dicessi nulla

However, including io can be helpful for emphasis or clarity. In this sentence, it helps clearly contrast:

• il tassista did something
• io did not say anything

So the pronoun is not required, but it is very natural and useful here.

In this sentence, nulla and niente mean basically the same thing:

• senza che io dicessi nulla
• senza che io dicessi niente

Both mean without me saying anything.

A few notes:

• nulla can sound a little more formal or literary in some contexts
• niente is extremely common in everyday speech

But in a sentence like this, either one is normal.

This is a very natural Italian structure:

• Quando..., main clause

So the sentence begins with the time clause:

• Quando il tassista ha visto la strada chiusa = When the taxi driver saw the road was closed

and then gives the main action:

• ha preso una deviazione = he took a detour

This order highlights the cause or triggering event first, then the response.

Italian could rearrange parts of the sentence, but this version is very standard and easy to follow.

Not really in this sentence. Here quando is best understood as when, introducing the moment at which the driver noticed the road closure.

So the sense is:

• When the taxi driver saw that the road was closed, he took a detour.

If the idea were more clearly while, Italian would often use other structures, depending on context.

Here the sentence describes one event leading to another, so when is the right interpretation.

Yes. Italian often uses verbs of perception like vedere with a direct object plus a description of its state.

So:

• ha visto la strada chiusa

literally resembles:

• he saw the road closed

But in natural English, we usually say:

• he saw that the road was closed

This structure is very common in Italian and worth getting used to. You may see similar patterns such as:

• ho trovato la porta aperta = I found the door open
• l’ho vista stanca = I saw her tired / she looked tired

So this sentence uses a very typical Italian pattern.