يتبادل شاهد العيان البيانات مع السائق الآخر.

Because starting with the verb is very common in Modern Standard Arabic.

This sentence has a verb–subject–object pattern:

• يتبادل = exchanges / is exchanging
• شاهد العيان = the eyewitness
• البيانات = the data / information
• مع السائق الآخر = with the other driver

So the structure is:

يتبادل شاهد العيان البيانات مع السائق الآخر
= The eyewitness exchanges information with the other driver.

Arabic could also say:

شاهد العيان يتبادل البيانات مع السائق الآخر

That version is also correct, but it puts the subject first and can sound a bit more emphatic about the eyewitness.

يتبادل comes from the verb تبادل, which means to exchange.

This verb often has a reciprocal sense, meaning that two sides exchange something with each other.

So here:

يتبادل ... البيانات
means exchanges data/information

and with مع السائق الآخر, it becomes:

exchanges information with the other driver

The form is the imperfect tense, so depending on context it can mean:

• exchanges
• is exchanging
• sometimes even will exchange if the context points to the future

Because the grammatical subject is singular:

شاهد العيان = the eyewitness

So the verb is singular too.

The idea of mutual exchange is already built into the verb يتبادل, and the other participant is added with:

مع السائق الآخر = with the other driver

So Arabic is not saying only one person is acting alone. It is saying that the eyewitness is engaged in an exchange with the other driver.

شاهد العيان is a standard expression meaning eyewitness.

It is best learned as a fixed phrase. Idiomatically, it means:

• an eyewitness
• someone who personally saw the event

The word عيان here is not simply the everyday word eye. It relates to direct seeing / seeing with one’s own eyes.

So the phrase means something like:

a witness of direct sight
which is why the natural English translation is eyewitness.

Because this phrase behaves like an iḍāfa (construct phrase), or at least very much like one.

In this type of structure:

• the first noun usually does not take ال
• the second noun can carry definiteness

So:

• شاهد العيان = the eyewitness

Even though شاهد has no ال, the whole phrase is definite because of the structure.

This is a very common thing in Arabic, and it can feel strange to English speakers at first.

البيانات is the plural of بيان in this context, and it usually means:

• data
• details
• information

In a sentence like this, especially if the context is an accident or report, it may mean things like:

• contact details
• insurance details
• identifying information

So the exact English wording depends on context, but information/details is often the safest understanding.

It is the direct object because it is the thing being exchanged.

The verb is:

يتبادل = exchanges

What is being exchanged?

البيانات = the information/data

So البيانات is in the accusative case.

A very important detail:

Although it is accusative, البيانات ends with a sound that looks like a genitive ending to beginners. That is because it is a sound feminine plural, and in that pattern:

• nominative: -اتُ
• accusative: -اتِ
• genitive: -اتِ

So here the accusative form is:

البَياناتِ

not البَياناتَ.

مع means with.

After a verb like يتبادل, Arabic often uses مع to show the other participant in the exchange:

يتبادل البيانات مع السائق الآخر
= exchanges information with the other driver

Also, مع is a preposition, so the noun after it is in the genitive case.

That is why, in full vowelled Arabic, you would read:

مَعَ السّائِقِ الآخَرِ

الآخر means the other.

It is an adjective describing السائق:

• السائق = the driver
• الآخر = the other

In Arabic, adjectives usually come after the noun and must agree with it in:

• gender
• number
• definiteness
• case

Since السائق is:

• masculine
• singular
• definite
• genitive here (because of مع)

the adjective must match it:

السائق الآخر
and, with full case endings:
السّائِقِ الآخَرِ

A fully vowelled version is:

يَتَبادَلُ شاهِدُ العِيانِ البَياناتِ مَعَ السّائِقِ الآخَرِ

A rough pronunciation guide:

yatabādalu shāhidu l-ʿiyāni l-bayānāti maʿa s-sāʾiqi l-ākhari

A few useful notes:

• شاهِدُ is nominative because it is the subject.
• العِيانِ is genitive as the second part of the construct phrase.
• البَياناتِ is accusative, but as a sound feminine plural it takes -i.
• السّائِقِ is genitive after مع.
• الآخَرِ matches السائق and is also genitive.

By itself, يتبادل is the imperfect form, which is broader than the English simple present.

Depending on context, it can mean:

• exchanges
• is exchanging
• does exchange
• sometimes a near-future sense

So this sentence could mean either:

• The eyewitness exchanges information with the other driver
• The eyewitness is exchanging information with the other driver

If Arabic wanted to make the future clearer, it could use something like:

• سيتبادل
• سوف يتبادل

to mean will exchange.