asa ha tyuurinzyou ga ippai nanode, zitensya de ha naku basu de gakkou ni ikimasu.

は marks 朝 as the topic: as for the morning or in the morning.

Here, 朝は does more than just give a time. It can also suggest contrast, like:

• In the morning, the bicycle parking area is full...
• Maybe at other times, that is not the case.

So 朝は can feel slightly like when it’s morning / as for mornings.

Because 駐輪場 is the thing being described by いっぱい.

In this sentence, いっぱい means full, so 駐輪場がいっぱい means:

• the bike parking area is full

A very common pattern is:

• A が いっぱい = A is full

So が marks the subject of that description.

Here, いっぱい means full.

It often means a lot or many in other contexts, but in this sentence it means:

• the bicycle parking area is full
• there is no room left

So this is not I have lots of parking lots or anything like that. It is specifically describing the parking area as being filled up.

なので is a polite, smooth, explanatory way to say so / because.

A quick comparison:

• ので: because, since
• なので: a form often used after nouns and na-adjectives
• だから: so, therefore; a bit more direct

Since いっぱい behaves like a na-adjective / noun-like predicate in this kind of usage, なので fits naturally:

• 駐輪場がいっぱいなので = because the bike parking area is full

It sounds natural and slightly softer than だから.

Here, で marks the means of transportation.

So:

• 自転車で = by bicycle
• バスで = by bus

This is a very common use of で:

• 電車で行く = go by train
• 車で行く = go by car

ではなく means not ... but ... or rather than ....

So:

• 自転車ではなく バスで = not by bicycle, but by bus

It connects two contrasting choices.

You can think of it as:

• A ではなく B = not A, but B

In this sentence:

• 自転車ではなくバスで学校に行きます
• I go to school by bus, not by bicycle

Yes, very often.

For example:

• 自転車じゃなくて、バスで学校に行きます。

This means the same basic thing, but the tone is more casual.

A rough comparison:

• ではなく = more formal/written/neat
• じゃなくて = more conversational

So the original sentence sounds a bit more careful or textbook-like.

Because に marks the destination of movement.

• 学校に行きます = go to school

With verbs like 行く, 来る, and 帰る, に often marks the place you are going to.

So:

• 学校に = to school

Japanese often leaves out the subject when it is already understood from context.

So even though English usually needs I, Japanese does not have to say it:

• (私は) バスで学校に行きます

If the speaker is obviously talking about their own routine, 私は is unnecessary.

This omission is extremely common in Japanese.

It can, yes.

Because は often creates a contrast, 朝は may suggest something like:

• In the morning, the bicycle parking area is full, so I go to school by bus.
• Maybe at other times, going by bicycle is possible.

That implication depends on context, but many learners should notice that は often carries this kind of contrastive feeling.

Yes.

駐輪場 means a place where bicycles or similar vehicles are parked.

Breakdown:

• 駐 = park/stop
• 輪 = wheel
• 場 = place

So it is a bicycle parking area or bike parking lot.

That is why the sentence mentions 自転車 afterward: the parking issue is specifically about bicycles.

Because the first part gives the reason, and the second part gives the result.

Structure:

• 朝は駐輪場がいっぱいなので、 = Because the bicycle parking area is full in the morning,
• 自転車ではなくバスで学校に行きます。 = I go to school by bus instead of by bicycle.

This is a very common Japanese pattern:

• Reason + ので, Result

The comma is not always absolutely required, but it helps readability.

Usually, 朝は is better here.

朝に simply marks a point in time, like at morning, but with general time words such as 朝, 今日, 明日, 毎日, Japanese often does not need に.

Also, 朝は gives the useful topic/contrast nuance:

• As for the morning...

So in this sentence, 朝は sounds more natural than 朝に.