Στον δρόμο χρειάζεται πολλή προσοχή, ειδικά όταν έχει κίνηση.

Στον is a contraction of σε + τον.

• σε = in / at / on / to
• τον = the masculine accusative singular article

So:

• σε τον δρόμο → στον δρόμο

The noun δρόμος means road, and after σε, Greek normally uses the accusative:

• nominative: ο δρόμος
• accusative: τον δρόμο

In this sentence, στον δρόμο is not just a literal location. It often means something broader like:

• on the road
• when driving
• in road situations
• in traffic

So it sets the context for the whole sentence.

Because δρόμο is the accusative singular form.

The dictionary form is:

• ο δρόμος = the road

But after σε (which becomes στον here), Greek uses the accusative:

• στον δρόμο = on the road

This is very common in Greek:

• στον φίλο = to the friend
• στον κήπο = in the garden
• στον δρόμο = on the road

So δρόμος changes to δρόμο because of the grammar required by σε.

Here χρειάζεται means something like:

• is needed
• requires
• takes

It is from the verb χρειάζομαι / χρειάζεται, and in this sentence it is used impersonally.

So:

• Στον δρόμο χρειάζεται πολλή προσοχή
  = On the road, a lot of attention is needed

Greek often uses this kind of singular verb form in impersonal statements, similar to English it takes or there is a need for.

There is no explicit subject like you. The idea is general:

• When you are on the road, a lot of attention is needed.

Because Greek often makes general statements without saying you explicitly.

English often says:

• You need to pay a lot of attention on the road.

Greek can express the same idea more impersonally:

• Στον δρόμο χρειάζεται πολλή προσοχή.

This sounds natural and general, like:

• On the road, a lot of attention is required.

Greek often leaves out subjects when they are understood from context, and in this case the sentence is framed as a general truth rather than direct advice to one person.

Because προσοχή is a feminine noun, and here πολλή is an adjective agreeing with it.

• η προσοχή = attention
• πολλή προσοχή = a lot of attention

Greek adjectives must agree with the noun in gender, number, and case.

Here:

• προσοχή = feminine singular
• so the adjective must also be feminine singular: πολλή

Compare:

• πολλή προσοχή = a lot of attention
• πολύ νερό = a lot of water
  because νερό is neuter

This is a very common point for learners, because πολύ can also be an adverb meaning very, but here it is not an adverb.

They can be different parts of speech.

1. πολλή = feminine adjective

It agrees with a feminine noun.

• πολλή προσοχή = a lot of attention
• πολλή δουλειά = a lot of work

2. πολύ = neuter adjective or adverb

As a neuter adjective:

• πολύ νερό = a lot of water

As an adverb:

• πολύ καλός = very good
• τρέχει πολύ = he/she runs a lot

In your sentence, προσοχή is feminine, so the correct form is πολλή.

Because Greek often omits the article in expressions of quantity or general meaning.

• πολλή προσοχή = a lot of attention

This is indefinite and general, not the attention.

If you said η πολλή προσοχή, it would sound much more specific and marked, like talking about a particular attention already known in context. That is not what this sentence is doing.

So the article is omitted because the phrase means a lot of attention in a general sense.

Ειδικά means:

• especially
• particularly

In this sentence:

• Στον δρόμο χρειάζεται πολλή προσοχή, ειδικά όταν έχει κίνηση.
• On the road, a lot of attention is needed, especially when there is traffic.

Greek adverbs like ειδικά are fairly flexible in position, but the placement here is very natural because it adds extra emphasis to the condition that follows.

You may also see it in other positions, for example:

• Ειδικά στον δρόμο χρειάζεται πολλή προσοχή.
  = Especially on the road, a lot of attention is needed.

The meaning changes slightly depending on what is being emphasized.

Όταν means when.

It introduces a time clause:

• όταν έχει κίνηση = when there is traffic

After όταν, Greek often uses the present tense to talk about something habitual or generally true, as here.

So this sentence means something like:

• especially when there is traffic
• especially whenever traffic is heavy

Greek uses the present tense naturally for repeated or typical situations.

Because έχει literally means it has, but Greek very often uses έχει in expressions where English uses there is / there are.

So:

• έχει κίνηση = literally it has traffic
• natural English: there is traffic / traffic is heavy

This is a very common Greek pattern. For example:

• Έχει κόσμο. = There are people / It’s crowded.
• Έχει ζέστη. = It’s hot.
• Έχει πρόβλημα. = There is a problem.

So όταν έχει κίνηση is an idiomatic, natural Greek way to say when there is traffic.

Because κίνηση here is being used in a general, idiomatic sense meaning traffic.

• έχει κίνηση = there is traffic / traffic is heavy

Greek often leaves out the article in these set expressions when talking about something non-specific or general.

If you said την κίνηση, it would sound more specific, as if you meant the traffic in a particular known sense, which is not the basic idiomatic phrasing here.

So:

• έχει κίνηση = natural, general expression
• έχει την κίνηση = not the normal choice here

Literally, κίνηση means movement.

But in everyday Greek, it very often means:

• traffic
• road traffic
• congestion

depending on context.

So in road-related situations:

• Έχει κίνηση. = There is traffic.
• Πολύ κίνηση σήμερα. = A lot of traffic today.

This is a normal and very common use of the word.

Yes. Even though the Greek sentence is impersonal, a natural English translation can be more personal if that sounds better in context.

Greek:

• Στον δρόμο χρειάζεται πολλή προσοχή, ειδικά όταν έχει κίνηση.

Possible English renderings:

• On the road, a lot of attention is needed, especially when there is traffic.
• You need to be very careful on the road, especially when traffic is heavy.
• You need to pay close attention on the road, especially when there’s traffic.

So the Greek grammar is impersonal, but English may prefer a more direct version.

The structure is:

• Στον δρόμο = context/location
• χρειάζεται = impersonal verb
• πολλή προσοχή = what is needed
• ειδικά όταν έχει κίνηση = added time/circumstance clause

So the sentence is built like this:

On the road + is needed + a lot of attention + especially when there is traffic

Greek word order is often flexible, but this order sounds natural and clear. It first sets the situation, then gives the general statement, then adds the special case.

Yes. Both are understandable, but they are slightly different in feel.

• όταν έχει κίνηση = very common, everyday, idiomatic
• όταν υπάρχει κίνηση = also correct, a bit more literal/formal as when traffic exists / when there is traffic

In normal spoken Greek, έχει κίνηση is extremely common and natural.

So for learners, έχει κίνηση is definitely worth remembering as a set phrase.