Машины въезжают, в то время как сотрудник проверяет аппарель.

Машины is the plural of машина and here means cars, vehicles, or machines, depending on context. Since the subject is plural, the verb also has to be plural.

• машина = singular
• машины = plural

The verb въезжают is the 3rd person plural form, so it matches машины:

• машина въезжает = the vehicle drives in
• машины въезжают = the vehicles drive in

So the agreement is the same basic idea as in English:

• The car drives in
• The cars drive in

Въезжают comes from въезжать, which means to drive in, to enter by vehicle, or to move into something while riding or driving.

It is built from:

• ехать = to go / ride / drive by transport
• prefix в- = into
• so въезжать = to go/drive into

In this sentence, машины въезжают suggests that the vehicles are entering some place, such as a building, a ferry, a loading area, or a garage.

Russian uses different verbs depending on the type of movement.

• идти / ходить are for going on foot
• ехать / ездить are for going by transport or in a vehicle

Since машины are vehicles, Russian uses the ехать family, not the walking verbs.

So:

• люди входят = people walk in / enter
• машины въезжают = vehicles drive in

That distinction is very important in Russian and often feels unusual to English speakers, since English just uses go in many situations.

Въезжают is imperfective.

Its infinitive is въезжать. The perfective partner is usually въехать.

Here the imperfective is used because the sentence describes an action in progress or a general ongoing event:

• Машины въезжают = the vehicles are driving in / are entering

This fits well with the second action:

• сотрудник проверяет аппарель = the employee is checking the ramp

So the sentence presents two actions happening at the same time.

Compare:

• Машины въезжают = the vehicles are driving in / entering
• Машины въехали = the vehicles drove in / entered completely

В то время как means while, whereas, or at the same time that, depending on context.

In your sentence, it means while:

• Машины въезжают, в то время как сотрудник проверяет аппарель.
• The vehicles are entering while the employee checks/is checking the ramp.

It is correct and fairly common, but it is a bit more formal or heavier than just пока in some contexts.

Possible alternatives:

• Машины въезжают, пока сотрудник проверяет аппарель.
• Машины въезжают, когда сотрудник проверяет аппарель.
  This changes the meaning slightly.

So в то время как is a good choice when you want to emphasize that two actions are happening simultaneously.

Russian normally uses a comma to separate clauses in complex sentences, especially when they are joined by conjunctions like когда, пока, потому что, если, and в то время как.

Here there are two clauses:

1. Машины въезжают
2. сотрудник проверяет аппарель

Since they are connected by в то время как, a comma is required.

So the comma is standard Russian punctuation, not optional here.

Сотрудник is the subject of the second clause, so it is in the nominative case.

In:

• сотрудник проверяет аппарель

the employee is the one doing the action, so nominative is used.

This is the dictionary form:

• сотрудник = employee / staff member

If it were in another role, the form would change. For example:

• Я вижу сотрудника = I see the employee
  Here it becomes сотрудника because it is the direct object.

Аппарель is in the accusative case because it is the direct object of проверяет.

The verb:

• проверять = to check / inspect

So the thing being checked takes the accusative:

• проверяет аппарель = checks the ramp

Now, аппарель is a feminine noun ending in a soft sign ь. For many feminine nouns of this type, the accusative singular looks the same as the nominative singular.

So:

• nominative: аппарель
• accusative: аппарель

That can be confusing because the form does not visibly change, but the grammatical role is different.

Аппарель usually means a loading ramp, gangway, or vehicle ramp, especially in technical, transport, shipping, or military contexts.

It is not one of the most everyday Russian words, so many learners will meet it mainly in specific contexts such as:

• ferries
• cargo loading
• aircraft or military vehicles
• loading docks

So in this sentence, it likely refers to the ramp the vehicles are using or are about to use.

Yes. Russian word order is more flexible than English, although not completely free. You could say:

• В то время как сотрудник проверяет аппарель, машины въезжают.

This means essentially the same thing:

• While the employee checks the ramp, the vehicles enter.

The difference is mainly one of emphasis:

• Машины въезжают... puts focus first on the vehicles entering.
• В то время как сотрудник проверяет аппарель... puts the time/background clause first.

Both are natural.

Russian present tense often covers both simple present and present continuous meanings that English separates.

So:

• проверяет can mean checks
• or is checking

In this sentence, because it is paired with another ongoing action, the most natural English translation is often:

• is checking

But Russian itself does not need a separate form for is checking.

The same is true for въезжают:

• enter
• are entering

Context tells you which English version fits best.

Yes. Машина is a very flexible word in Russian.

Depending on context, машины can mean:

• cars
• vehicles
• machines

In everyday speech, машина very often means car, but in a sentence involving an аппарель, the broader meaning vehicles may be more natural.

So the exact English choice depends on the situation being described.

Yes, автомобили could work if you specifically mean cars/automobiles.

Compare:

• машины = more general; can mean cars, vehicles, or machines depending on context
• автомобили = specifically automobiles/cars

So:

• Автомобили въезжают, в то время как сотрудник проверяет аппарель.

This is grammatical, but slightly more specific and sometimes a bit more formal or technical than машины.

Grammatically, сотрудник is a masculine noun. It usually refers to a male employee, or sometimes to a person of unspecified gender in certain contexts, depending on style and usage.

If you know the employee is female, Russian would normally use:

• сотрудница

So:

• ...в то время как сотрудница проверяет аппарель.

English often uses gender-neutral employee, but Russian commonly marks gender in nouns like this.