Pe când șoferul mergea pe carosabil, mașina din față a frânat.

Pe când means while or at the time when. In this sentence, it sets the background for another event:

• Pe când șoferul mergea pe carosabil... = While the driver was going/driving on the road...

Compared with când, pe când often sounds a bit more literary or narrative. In everyday speech, many Romanians would also say:

• Când șoferul mergea pe carosabil...
• În timp ce șoferul mergea pe carosabil...

All of these can work here, but pe când gives a slightly more storytelling feel.

Mergea is the imperfect tense, and it shows an action that was in progress or formed the background in the past.

So:

• șoferul mergea = the driver was going / was driving

The sentence then contrasts that ongoing background action with a shorter, completed event:

• mașina din față a frânat = the car in front braked

This is a very common Romanian pattern:

• imperfect for the ongoing situation
• perfect compus for the event that interrupts or happens during it

So the tense choice is very similar to English:

• was driving ... braked

In a frânat, the a is the auxiliary verb used to form the perfect compus, one of the main past tenses in Romanian.

So:

• a frânat = he/she/it braked or has braked depending on context

Here, a is not the dictionary form a frâna. It is the auxiliary for the 3rd person singular.

A quick comparison:

• eu am frânat = I braked
• tu ai frânat = you braked
• el/ea a frânat = he/she braked

So in this sentence, mașina is singular, which is why the verb is a frânat.

Yes. A merge basically means to go, to move, or to travel. Depending on context, it can often be translated in different ways.

In this sentence, because the subject is șoferul and the setting is pe carosabil, English would naturally say:

• the driver was driving
• or more literally, the driver was going

Romanian does not always need a special verb like to drive where English does. The context tells you that this is movement by vehicle.

That said, Romanian also has a conduce, which more specifically means to drive. So you could also say:

• Pe când șoferul conducea...

That would sound more explicitly like was driving.

Yes, absolutely.

• mergea = was going / was moving / was driving, depending on context
• conducea = was driving

So:

• Pe când șoferul mergea pe carosabil...
• Pe când șoferul conducea pe carosabil...

Both are possible, but they are not exactly identical in feel.

mergea is broader and describes movement.
conducea focuses specifically on the act of driving.

In this sentence, conducea may sound a bit more precise to an English speaker, but mergea is still perfectly natural because the subject is already the driver.

The preposition pe here means on.

• carosabil = the roadway / the drivable part of the road
• pe carosabil = on the roadway

Romanian often uses pe for movement or location on a surface:

• pe drum = on the road
• pe stradă = on the street
• pe trotuar = on the sidewalk
• pe carosabil = on the roadway

So this is very straightforward: the driver was moving on the roadway.

Carosabil is a fairly specific traffic-related word. It means the part of the road used by vehicles, that is, the roadway or carriageway.

It does not mean the whole street in a general sense. It specifically refers to the vehicle-use section, as opposed to, for example:

• trotuar = sidewalk
• carosabil = roadway

So the sentence sounds a little formal or official because carosabil is a more precise word than something like drum or stradă.

Din față here means the one in front or the one ahead.

So:

• mașina din față = the car in front / the car ahead

This phrase works like a noun plus a descriptive expression identifying which car.

By contrast, în față usually means in front as a location:

• Mașina este în față. = The car is in front.

So the difference is roughly:

• mașina din față = the front car / the car ahead
• mașina în față = the car is in front

In your sentence, din față is the natural choice because it identifies the specific car.

The -ul is the definite article, attached to the end of the noun.

So:

• șofer = driver
• șoferul = the driver

This is one of the first big differences English speakers notice in Romanian: instead of putting the before the noun, Romanian usually adds it to the end.

Some examples:

• băiat = boy

• băiatul = the boy

• drum = road
• drumul = the road

So șoferul simply means the driver.

For the same reason:

• mașină = car
• mașina = the car

In mașina din față, Romanian means the car in front or the car ahead. It is a specific car, not just any car.

So both main nouns in the sentence are definite:

• șoferul = the driver
• mașina din față = the car in front

Yes. Romanian word order is fairly flexible.

The original sentence is:

• Pe când șoferul mergea pe carosabil, mașina din față a frânat.

You could also say:

• Mașina din față a frânat pe când șoferul mergea pe carosabil.

That is grammatically possible, but it sounds a little less natural in a neutral narrative context. The original order is better if you want to set the scene first and then introduce the event.

Romanian often puts the background clause first when telling a story:

• While X was happening, Y happened.

So the given order feels very normal.

Yes. The comma separates the subordinate time clause from the main clause.

Structure:

• Pe când șoferul mergea pe carosabil = subordinate clause
• mașina din față a frânat = main clause

In English, you would also normally use a comma when the while clause comes first:

• While the driver was driving on the roadway, the car in front braked.

So the punctuation works very similarly here.

A very useful way to see it is:

• Pe când
  • imperfect = background action in progress
• perfect compus = completed event that happens during that background action

So this sentence follows a common storytelling pattern:

• Pe când șoferul mergea pe carosabil
  ongoing background

• mașina din față a frânat
  sudden/completed event

This pattern is extremely common in Romanian narrative, just as in English:

• While he was doing X, Y happened.

It is mostly neutral, but with a slightly formal touch because of two things:

• pe când sounds a little more literary than plain când
• carosabil is a technical or official-sounding word for roadway

A more everyday version might be something like:

• Când șoferul mergea pe drum, mașina din față a frânat.
• În timp ce șoferul conducea, mașina din față a frânat.

So the original is perfectly correct, but it is not the most casual possible phrasing.