Ik was rustig, ook toen de trein vertraagd was.

Because there are two clauses, and each clause has its own verb:

• Ik was rustig = I was calm
• toen de trein vertraagd was = when the train was delayed

In Dutch, just like in English, each clause needs its own finite verb. Both clauses are in the past, so both use was, the singular past form of zijn (to be).

Here, rustig means calm or composed.

It can also mean things like:

• quiet
• peaceful
• relaxed

But in this sentence, because it describes a person’s emotional state, calm is the best fit.

A native English speaker might wonder about kalm. That is also possible in Dutch, but rustig is extremely common and natural.

Literally, ook toen means also when or also at the time when, but in natural English it often comes across as:

• even when
• including when
• also when

So in this sentence, ook toen emphasizes that the speaker stayed calm in that situation too.

It adds the idea:

• I was calm, even when the train was delayed.

Because toen introduces a subordinate clause, and in Dutch subordinate clauses, the verb usually goes to the end.

So:

• main clause: Ik was rustig
• subordinate clause: toen de trein vertraagd was

This is a very important Dutch pattern:

• Ik weet dat hij thuis is.
• Ze zei dat het moeilijk was.
• Ik bleef rustig toen de trein vertraagd was.

In subordinate clauses, Dutch often places the conjugated verb at the end, or near the end if there is more than one verb.

It is a past participle of vertragen (to delay), but in this sentence it functions much like an adjective with zijn:

• de trein was vertraagd = the train was delayed

This is very similar to English. Compare:

• The door was closed
• The train was delayed

So vertraagd comes from a verb, but in this structure it describes the state of the train.

Because rustig is a predicate adjective here, not an adjective placed before a noun.

Compare:

• Ik was rustig. → predicate adjective, no extra ending
• een rustige man → adjective before a noun, so it gets -e

This is a common Dutch pattern:

• Het huis is groot.
• een groot huis
• de grote huizen

So in Ik was rustig, the plain form rustig is correct.

Yes, and it is very natural. But the meaning is slightly different.

• Ik was rustig = I was calm
• Ik bleef rustig = I stayed calm / remained calm

So:

• Ik was rustig, ook toen de trein vertraagd was. focuses on your state.
• Ik bleef rustig, ook toen de trein vertraagd was. emphasizes that the delay did not make you lose your calm.

In many contexts, bleef rustig may sound even more natural in English because we often say I stayed calm.

Because toen is typically used for something that happened at a specific time in the past.

Here, the sentence refers to a particular past situation:

• the train was delayed
• you were calm at that time

So toen is the natural choice.

Very roughly:

• toen = when for a specific past event
• als = if/when for repeated or conditional situations
• wanneer = when, often more neutral or formal, and common in questions

Examples:

• Toen de trein vertraagd was, bleef ik rustig.
• Als de trein vertraagd is, raak ik soms geïrriteerd. = whenever/if the train is delayed...

Yes, the comma is normal and correct here because it separates the main clause from the added clause:

• Ik was rustig, ook toen de trein vertraagd was.

Dutch punctuation often uses a comma before subordinate clauses, especially when the extra clause comes after the main statement and adds information clearly.

You may sometimes see variation in informal writing, but with this sentence, the comma is standard.

Yes. Dutch allows some flexibility.

For example, you could say:

• Ook toen de trein vertraagd was, was ik rustig.

This means the same thing, but the emphasis changes slightly. It puts more focus on the time/situation first: Even when the train was delayed, I was calm.

Notice what happens when the subordinate clause comes first:

• Ook toen de trein vertraagd was, was ik rustig.

After the opening clause, the main clause follows normal Dutch inversion, so the verb was comes before ik.

In this sentence, it most naturally refers to a temporary state in that situation.

• Ik was rustig = I was calm
• in that moment / under those circumstances

Dutch zijn + adjective can describe either a temporary state or a more lasting quality, depending on context. Here, because of ook toen de trein vertraagd was, it clearly points to a specific event, so it sounds temporary.