oneul jadongchadeuri gireseo keuge chungdolhaesseoyo.

오늘 is a time expression, and Korean often uses time words without any particle.

So 오늘 자동차들이 길에서 크게 충돌했어요 is completely normal.

You could also say 오늘은 if you want to make today the topic or add contrast, like:

• 오늘은 자동차들이 길에서 크게 충돌했어요.
  = As for today / Today, the cars had a major collision.

Putting 오늘 first is very common, but Korean word order is flexible, so other placements are possible too.

The 들 makes 자동차 explicitly plural:

• 자동차 = car / cars
• 자동차들 = cars

Korean often leaves plural unmarked if the meaning is already clear, but 들 is used when the speaker wants to clearly show there were multiple cars.

So 자동차들이 emphasizes that more than one car was involved.

이/가 marks the subject of the sentence.

Here, the cars are the ones doing the action of colliding, so they take the subject marker.

It becomes 들이 because:

• 자동차들 ends in a consonant sound (ㄹ)
• after a consonant, the subject marker is 이

So:

• 자동차들 + 이 = 자동차들이

If the noun ended in a vowel, you would use 가 instead.

에서 marks the place where an action or event happens.

Since the collision happened on the road, 길에서 is the natural choice.

• 길에서 충돌했어요 = collided on the road

By contrast, 에 is often used for:

• destination
• existence
• time
• some other non-action location uses

So in this sentence, 에서 is the correct particle because 충돌하다 is an event happening at that place.

크게 is the adverb form of 크다 (to be big), but in this kind of sentence it means something more like:

• severely
• badly
• on a large scale

So 크게 충돌했어요 means the collision was serious or major, not physically big in a literal English way.

Also, it does not mean loudly here.

A learner-friendly way to understand it is:

• 큰 충돌 = a big collision
• 크게 충돌하다 = to collide badly / severely

It comes from 충돌하다:

• 충돌 = collision
• 하다 = to do
• 충돌하다 = to collide

Then it is put into:

• past tense: 했-
• polite ending: -어요

So:

• 충돌하다 → 충돌했어요

This is a very common Korean pattern:

• 공부하다 → 공부했어요
• 운동하다 → 운동했어요
• 충돌하다 → 충돌했어요

In this sentence, 충돌하다 works without a direct object because the meaning is understood as the cars collided with each other.

Korean does not always need to spell that out if the context is obvious.

If you wanted to make it clearer, you could say:

• 자동차들이 서로 충돌했어요.
  = The cars collided with each other.

So the original sentence is natural even without an object.

Yes. Korean word order is fairly flexible, as long as the verb stays near the end.

For example, these are all possible:

• 오늘 자동차들이 길에서 크게 충돌했어요.
• 오늘 길에서 자동차들이 크게 충돌했어요.
• 자동차들이 오늘 길에서 크게 충돌했어요.

They all mean basically the same thing, but the emphasis may shift slightly depending on what comes first.

Korean often moves time and place expressions around more freely than English does.

Yes, you could say 차들.

• 자동차들 sounds a bit more full/formal
• 차들 sounds more everyday and conversational

So:

• 오늘 차들이 길에서 크게 충돌했어요.
  is also natural.

In some contexts, Koreans might even say:

• 차 여러 대가 길에서 크게 충돌했어요.
  = Several cars collided badly on the road.

That can sound especially natural when talking about vehicles, because Korean often counts vehicles with 대.

크게 충돌했어요 is understandable and natural enough, especially if you mean a major collision.

But depending on context, Koreans might also say:

• 심하게 충돌했어요 = collided severely
• 세게 부딪혔어요 = hit hard
• 큰 사고가 났어요 = a big accident happened

So 크게 is not wrong, but learners should know that Korean has several natural ways to describe a serious crash.