ame no hi ni kuruma o untensuru toki, shingou ni chuui o shimasu.

雨 and 日 are both nouns, so Japanese usually connects them with の.

• 雨 = rain
• 日 = day
• 雨の日 = a rainy day / a day of rain

Here, の works like of or shows that one noun describes another noun. So 雨の日 literally means something like a day of rain.

The に marks a time expression.

So:

• 雨の日に = on a rainy day / when it is a rainy day

In this sentence, it tells you when the action happens.

A useful pattern is:

• 時間 + に = at/on a time

For example:

• 日曜日に = on Sunday
• 朝に = in the morning
• 雨の日に = on a rainy day

Japanese usually puts the object before the verb.

So:

• 車 = car
• を = marks the direct object
• 運転する = to drive

Therefore:

• 車を運転する = to drive a car

This is normal Japanese word order: object + verb.

とき means when or at the time of.

In this sentence:

• 車を運転するとき = when driving a car / when you drive a car

The part before とき describes what kind of time it is. So the whole clause 車を運転する modifies とき.

A good way to think about it is:

• [dictionary form verb] + とき = when doing that action
• 食べるとき = when eating
• 寝るとき = when sleeping
• 運転するとき = when driving

Because 注意する works differently from a simple direct-object verb.

Here:

• 注意 is a noun meaning attention / caution
• する turns it into a verb: to pay attention / to be careful
• The thing you pay attention to is marked with に

So:

• 信号に注意をする = to pay attention to the traffic signal

That is why 信号 takes に, not を.

You can think of it like this:

• A に 注意する = pay attention to A

Because 注意 is a verbal noun, and in this pattern it behaves like the object of する.

So:

• 注意をする = to do attention → idiomatically, to pay attention

This is a very common pattern in Japanese:

• 勉強をする = to study
• 運動をする = to exercise
• 注意をする = to pay attention

So even though English would not say do attention, Japanese uses 注意 + を + する naturally.

Yes. 注意します is also very common.

Both are understandable:

• 信号に注意をします
• 信号に注意します

The version without を often sounds a little more streamlined in modern Japanese.

So:

• 注意をする = full noun + する pattern
• 注意する = very common shortened verbal form

Both are correct.

In this context, it means traffic signal / traffic light.

The word 信号 can mean signal in a broader sense, but when you are talking about driving, it normally means the road signal.

So in this sentence, 信号に注意をします means paying attention to traffic lights or signals while driving.

Japanese often omits the subject when it is obvious from context.

So the sentence could mean:

• I pay attention to traffic signals when I drive on rainy days
• You should pay attention to traffic signals when driving on rainy days
• People pay attention to traffic signals when driving on rainy days

The exact subject depends on the situation. Japanese often leaves it unsaid if it is already understood.

In Japanese, the non-past form is used not only for future actions, but also for:

• habitual actions
• general truths
• repeated situations
• instructions or general advice

So here:

• 運転するとき = when driving
• 注意をします = pay attention / will pay attention / do pay attention

This makes sense for a general statement like when driving on rainy days, pay attention to traffic signals or I pay attention to traffic signals when driving on rainy days.

The comma just separates the when part from the main action.

So the sentence has two big parts:

• 雨の日に車を運転するとき
• 信号に注意をします

The comma helps the reader hear the pause:

• When driving a car on a rainy day, ...
• ... pay attention to the traffic signals.

It is not absolutely required in every case, but it is very natural here because the first part is fairly long.

Yes. The sentence is understandable, but many speakers might say something a little more natural, such as:

• 雨の日に車を運転するときは、信号に注意します。
• 雨の日に運転するときは、信号に注意します。
• 雨の日に車を運転するときは、信号をよく見ます。
• 雨の日の運転では、信号に気をつけます。

A very common everyday expression is:

• 気をつける = to be careful

So 信号に気をつけます can sound very natural too.

Still, the original sentence is grammatically understandable and good for studying these patterns.

Adding は gives a stronger as for when... or in the case of when... feeling.

Compare:

• 運転するとき、信号に注意します。
  = When driving, I pay attention to traffic signals.

• 運転するときは、信号に注意します。
  = When driving, as a rule / in that situation, I pay attention to traffic signals.

The は often adds contrast or emphasis, especially in advice or general rules. That is why ときは is very common in sentences like this.