eki no mae no miti ha abunai node, kodomo to issyo no toki ha hodoukyou wo tukatta hou ga ii desu.

Japanese often links nouns with の.

• 駅の前 = the front of the station / the area in front of the station
• 駅の前の道 = the road in front of the station

So the first の connects 駅 and 前, and the second の connects the whole phrase 駅の前 to 道.

は marks 道 as the topic: as for the road in front of the station...

This works well because the sentence is making a general comment or warning about that road.
If you used が, it would sound more like you are specifically identifying that road as the dangerous one.

So here:

• 道は危ない = That road is dangerous / As for that road, it’s dangerous

Japanese often leaves the subject unstated when it is obvious from context.

Here, the sentence is giving general advice, so the understood subject is something like:

• you
• one
• people

In natural English, that becomes something like you should use the footbridge or it’s better to use the footbridge.

ので means because or since.

• 危ないので = because it is dangerous

Compared with から, ので often sounds:

• a little softer
• more explanatory
• a bit more polite or less direct

That makes it very common in warnings, explanations, and advice.

In Japanese, non-final parts of a sentence are often kept in plain form, even when the sentence ends politely.

So this pattern is very normal:

• 危ないので、... いいです

The politeness is carried by the final です.
A lot of learners expect politeness on every part of the sentence, but Japanese does not always work that way.

It can mean either, depending on context.

Japanese nouns usually do not have to show singular/plural clearly. So 子供 can mean:

• a child
• children
• your child / your kids, depending on context

In this sentence, it is probably general advice, so English may naturally translate it as when you are with children, but when you are with a child is also grammatically possible.

Here, 一緒の is modifying とき.

• 子供と一緒 = together with a child / children
• 子供と一緒のとき = when you are together with a child / children

A useful comparison:

• 一緒に
  • verb
    
    • 子供と一緒に歩く = walk together with a child
• 一緒の
  • noun
    
    • 子供と一緒のとき = when you are with a child

So 一緒にとき would be wrong, because に does not connect directly to the noun とき in this structure.

は adds a topic/contrast nuance.

• 子供と一緒のときは = when you’re with children, (in that case)...

It highlights that situation as an important condition.

Compare:

• とき = neutral when
• ときに = at the time when / when
• ときは = when it comes to the case of... / when..., then...

In advice sentences, ときは is very common because it sets up the condition clearly.

歩道橋 is a pedestrian overpass, footbridge, or pedestrian bridge over a road.

It is specifically for people to cross safely above traffic.

The word breaks down like this:

• 歩道 = sidewalk / pedestrian path
• 橋 = bridge

So it is not just any bridge; it is a bridge meant for pedestrians.

This is a very common pattern:

• verb in past plain form + ほうがいい

It means:

• it’s better to...
• you should...
• it would be better to...

So:

• 歩道橋を使ったほうがいいです = it’s better to use the footbridge

Literally, ほう means side or option, so the pattern originally has the sense of the option of doing X is better.

Because in Vたほうがいい, the た form is part of a fixed grammar pattern. It does not mean the action already happened.

So:

• 行ったほうがいい = you should go
• 見たほうがいい = you should see/watch
• 使ったほうがいい = you should use

This is one of those cases where the past form is used for grammar, not for actual past time.

Japanese often uses 使う (to use) for things like facilities, tools, or options.

So 歩道橋を使う means use the footbridge as the safe route.

A different sentence could use 渡る:

• 歩道橋を渡る = cross the footbridge

The difference is:

• 使う focuses on choosing/utilizing it
• 渡る focuses on the physical act of crossing it

In this sentence, 使う fits well because the speaker is giving practical advice about what option to choose.

The comma separates the reason from the main advice:

• 駅の前の道は危ないので、 = Because the road in front of the station is dangerous,
• 子供と一緒のときは歩道橋を使ったほうがいいです。 = when you’re with children, it’s better to use the footbridge.

Japanese commas often show a natural pause and make longer sentences easier to read.