eki no tikaku no humikiri ga nagaku simatte ita node, gakkou ni sukosi okureta.

Both の connect nouns, but they do slightly different jobs in the chain.

• 駅の近く = the area near the station
  • 駅 = station
  • 近く = nearby area / vicinity
• 駅の近くの踏切 = the railroad crossing near the station

So the structure is:

• 駅 → modifies 近く
• 駅の近く → modifies 踏切

You can think of it as:

• [station]’s [nearby area]’s [railroad crossing]

In natural English, that becomes the railroad crossing near the station.

近く here is a noun meaning nearby place, vicinity, or area near something.

So:

• 駅の近く = near the station / the area near the station

This is different from using the adjective 近い directly. For example:

• 駅に近い踏切 = a crossing that is close to the station
• 駅の近くの踏切 = a crossing in the area near the station

Both are natural, but 駅の近くの踏切 is very common.

が marks the subject of the clause:

• 踏切が長く閉まっていた
• The railroad crossing was closed for a long time

So 踏切 is the thing being described as closed.

If you used は instead, it would sound more like you were setting the crossing up as the topic, with a contrastive or topical nuance. But in this sentence, が is the most natural way to introduce the thing that caused the problem.

Because 長い is an i-adjective, and here it modifies the verb phrase 閉まっていた.

To make an i-adjective modify a verb, you change -い to -く:

• 長い = long
• 長く = for a long time / long

So:

• 長く閉まっていた = was closed for a long time

This is the adverbial form of the adjective.

閉まっていた is the te-form + いる in the past:

• 閉まる = to close / to be closed
• 閉まっている = is closed
• 閉まっていた = was closed

In this sentence, it describes a continuing state in the past:

• 踏切が長く閉まっていた
• The crossing had been closed for a long time / was closed for a long time

For things like doors, shops, gates, or railroad crossings, 閉まっている often means is in the closed state, not is actively closing.

Because 閉まる is an intransitive verb, while 閉める is transitive.

• 閉まる = something closes / is closed
• 閉める = someone closes something

Here, the sentence focuses on the state of the crossing itself:

• 踏切が閉まっていた = the crossing was closed

If you used 閉める, you would need a person or agent doing the action, such as:

• 駅員が踏切を閉めた = The station worker closed the crossing

ので means because, since, or so. It gives the reason for what happened next.

• 踏切が長く閉まっていたので、学校に少し遅れた。
• Because the crossing was closed for a long time, I was a little late to school.

Compared with から, ので often sounds:

• a bit softer
• more explanatory
• a little more objective or polite

So:

• 〜ので = because / since, softer and explanatory
• 〜から = because, often more direct or conversational

Both could work here, but ので is very natural.

The comma separates the reason clause from the main clause:

• 踏切が長く閉まっていたので、
• 学校に少し遅れた。

It works like a pause in reading:

• Because the crossing was closed for a long time, I was a little late to school.

Japanese commas are often used more flexibly than English commas, but here it helps make the sentence easier to read.

The verb 遅れる often takes に to mark what someone is late for.

• 学校に遅れる = to be late for school
• 会社に遅れる = to be late for work
• 授業に遅れる = to be late for class

So に marks the target/event/destination that the lateness relates to.

Using を here would be incorrect.

少し means a little or slightly.

It modifies 遅れた:

• 少し遅れた = was a little late

So the speaker is not saying they were very late, only somewhat late.

You can compare:

• 少し遅れた = was a little late
• だいぶ遅れた = was quite late
• かなり遅れた = was fairly/considerably late

Japanese often leaves out subjects when they are obvious from context.

So even though there is no explicit 私は, the meaning is understood as something like:

• (私は) 学校に少し遅れた。
• (I) was a little late to school.

This is very normal in Japanese. If the speaker added 私は, it might be for emphasis, contrast, or clarity, but it is not necessary.

踏切 usually refers to the railroad crossing as a whole.

In real life, when Japanese says a 踏切 is 閉まっている, it usually means the crossing is blocked because the barrier is down and people or cars cannot pass.

So the sentence does not only mean that some object was physically shut; it means:

• the level crossing was closed off to traffic

Yes. Depending on context, natural English translations could be:

• was closed for a long time
• had been closed for a long time
• stayed closed for a long time

Japanese past forms do not always match English tense choices one-for-one. The key idea is that the crossing remained closed for a while, and that caused the lateness.

It breaks down like this:

• 駅の近くの踏切が
  = the railroad crossing near the station

  • subject marker

• 長く閉まっていたので、
  = because it was closed for a long time,

• 学校に少し遅れた。
  = I was a little late to school.

So the overall pattern is:

• [Reason] ので、[Result]

In this sentence:

• Reason: the crossing near the station was closed for a long time
• Result: the speaker was a little late to school

Yes, it would be very similar.

• 駅の近くの踏切 = the crossing near the station
• 駅の近くにある踏切 = the crossing that is located near the station

The version with にある is a little more explicit, because it literally says that exists/is located near the station. But in everyday Japanese, 駅の近くの踏切 is shorter and very natural.

That is a very common Japanese pattern. The reason or background information often comes first, and the main result comes later.

So instead of:

• I was late because...

Japanese often prefers:

• Because..., I was late.

That is exactly what happens here:

• 踏切が長く閉まっていたので、学校に少し遅れた。

This word order is completely natural in Japanese.