يوثق السائق الآخر الحادث المروري.

Because Arabic very commonly uses verb–subject–object (VSO) word order, especially in formal written language like Modern Standard Arabic.

So:

• يوثق = documents
• السائق الآخر = the other driver
• الحادث المروري = the traffic accident

This is completely normal in MSA.

You could also say:

• السائق الآخر يوثق الحادث المروري.

That uses subject–verb–object (SVO) order and is also correct, but the original VSO order is very standard and natural in formal Arabic.

يوثق is a present/future tense verb in MSA.

More specifically, it is:

• 3rd person
• masculine
• singular

So it means he documents, he is documenting, or sometimes he documents/will document, depending on context.

The dictionary form is usually given as وثّق (waththaqa) = to document / record / verify.

This verb is from Form II, which often has an intensive or causative sense. The doubled middle consonant is important here.

It is pronounced approximately:

• yuwath-thiqu

A more careful breakdown:

• yu-
• wath-
• thi-qu

Important detail:

• The ث sounds like th in think
• The doubled consonant comes from the underlying shadda in the verb pattern, even if short vowels and marks are not written in normal text

So the fully vowelled form would be something like:

• يُوَثِّقُ

Because both words are definite.

• السائق = the driver
• الآخر = the other

Together:

• السائق الآخر = the other driver

In Arabic, adjectives agree with the noun in definiteness, so if the noun has الـ (the), the adjective usually does too.

If you wanted another driver or an other driver in an indefinite sense, you would use something like:

• سائقٌ آخرُ = another driver

So the sentence specifically refers to a particular, known driver: the other driver.

Because Arabic adjectives normally come after the noun they describe.

So:

• السائق الآخر literally = the driver the-other
• natural English = the other driver

This is the normal noun + adjective order in Arabic.

The same thing happens in:

• الحادث المروري = the traffic accident
  • literally: the accident the-traffic-related

Because adjectives in Arabic usually match the noun they describe in definiteness.

Since السائق is definite (the driver), the adjective must also be definite:

• السائق الآخر = the other driver

If the noun were indefinite, the adjective would also be indefinite:

• سائقٌ آخرُ = another driver

This matching is a very important rule in Arabic adjective phrases.

For the same reason: المروري is an adjective describing الحادث, so it agrees with it in definiteness.

• الحادث = the accident
• المروري = traffic-related

Together:

• الحادث المروري = the traffic accident

Since the noun is definite, the adjective is also definite.

This is one of the easiest patterns to recognize in Arabic:

• definite noun + definite adjective

In this sentence, word order helps a lot.

The structure is:

• يوثق = verb
• السائق الآخر = subject
• الحادث المروري = object

So after the verb and subject, the final noun phrase is understood as what is being documented.

In fully vowelled classical-style grammar, the case endings would also show this:

• يُوَثِّقُ السَّائِقُ الآخَرُ الحَادِثَ المَرُورِيَّ
  • السائقُ الآخرُ = nominative subject
  • الحادثَ المروريَّ = accusative object

In normal everyday Arabic writing, these endings are usually not written, so learners often rely on position and context.

Because the subject is singular:

• السائق الآخر = the other driver

So the verb is also singular:

• يوثق = he documents

This is normal subject-verb agreement.

A useful extra note: in Arabic, when the verb comes before the subject, agreement can behave differently from English, especially with plural subjects. But here you do not need to worry about that, because the subject is singular and masculine, so the verb is straightforwardly 3rd person masculine singular.

Here it is an adjective.

• الحادث = accident
• المروري = traffic-related / road-traffic

So:

• الحادث المروري = the traffic accident

This adjective is a nisba adjective, a very common Arabic type of adjective often formed with -يّ.

Related noun:

• مرور = المرور = traffic / passing / transit

From that, Arabic forms:

• مروري = traffic-related

Because س is a sun letter.

When الـ comes before a sun letter, the l sound of الـ is assimilated to the next consonant.

So:

• written: السائق
• pronounced: as-sāʾiq

By contrast, in words beginning with a moon letter, the l is pronounced normally.

For example:

• الحادث is pronounced al-ḥādith
• المروري is pronounced al-murūrī

But:

• السائق is pronounced as-sāʾiq

In fully vowelled MSA, the sentence would be:

• يُوَثِّقُ السَّائِقُ الآخَرُ الحَادِثَ المَرُورِيَّ

The endings are:

• يُوَثِّقُ → verb in the indicative
• السَّائِقُ → nominative, because it is the subject
• الآخَرُ → nominative, agreeing with السائق
• الحَادِثَ → accusative, because it is the direct object
• المَرُورِيَّ → accusative, agreeing with الحادث

In normal printed Arabic, these short vowel endings are usually omitted, so you often see:

• يوثق السائق الآخر الحادث المروري

without the final vowel marks.

Possibly, depending on context, because وثّق can have related meanings such as:

• document
• record
• verify
• authenticate

But in a sentence about a driver and a traffic accident, the most natural meaning is usually:

• documents the traffic accident
• or records the traffic accident

For example, it could mean the driver is taking photos, filing a report, or officially recording what happened.

So the exact English choice depends on the situation, even though the Arabic wording stays the same.