Hoe drukker het bij de kruising is, des te voorzichtiger fiets ik in onze woonwijk.

It is a comparative correlative pattern. It expresses a link between two changing things:

• Hoe + comparative ...
• des te + comparative ...

It means the more ..., the more ... or sometimes the more ..., the less ..., depending on the adjectives you use.

So here the structure says that as one thing increases, another changes too:

• hoe drukker = the busier
• des te voorzichtiger = the more carefully / the more cautious

This is a very common Dutch pattern.

Not really. In this sentence, hoe is not asking a question. It is part of the fixed pattern hoe ..., des te ....

In this structure, hoe corresponds more closely to English the in a sentence like:

• The busier it is, the more carefully I cycle

So even though hoe often means how in other contexts, here it helps build a comparison.

Because they are comparatives.

• druk = busy

• drukker = busier

• voorzichtig = careful / cautious
• voorzichtiger = more careful / more cautious

Dutch usually forms the comparative with -er, much like English sometimes does with -er:

• small → smaller
• druk → drukker

For longer English adjectives, English often uses more, but Dutch still often uses -er:

• voorzichtig → voorzichtiger

Because after hoe + comparative, the clause behaves like a subordinate clause, so the finite verb goes to the end.

Compare:

• Main clause: Het is druk bij de kruising
• In this pattern: Hoe drukker het bij de kruising is

So the word order is normal for this kind of Dutch clause:

• het = subject
• bij de kruising = location
• is = finite verb at the end

Het is a dummy subject, similar to English it in:

• It is busy at the intersection

It does not refer to a specific object. It is just the subject Dutch needs in a sentence like Het is druk.

So:

• Het is druk bij de kruising = It is busy at the intersection

And in the comparative clause:

• Hoe drukker het bij de kruising is = The busier it is at the intersection

Dutch usually does not make adverbs the way English does with -ly.

So:

• voorzichtig can mean careful as an adjective
• but it can also function adverbially, meaning carefully

That means:

• Ik fiets voorzichtig = I cycle carefully
• Ik fiets voorzichtiger = I cycle more carefully

So even though voorzichtiger looks like an adjective, here it is functioning adverbially.

Because the second part is a main clause, and Dutch main clauses follow the verb-second rule.

The first position is taken by des te voorzichtiger, so the finite verb must come next:

• Des te voorzichtiger fiets ik ...

Structure:

• first position: des te voorzichtiger
• second position: fiets
• then subject: ik

If you started directly with the subject, you would get the normal order:

• Ik fiets voorzichtiger ...

But once des te voorzichtiger is moved to the front, inversion happens.

Des te is part of the fixed comparative expression. By itself, it does not mean something simple like therefore or so. In this structure, it means something like:

• all the more
• the more

So:

• des te voorzichtiger = all the more carefully / the more carefully

It is slightly more formal or written in tone than some other ways of expressing the same idea.

Yes. That is also very common in Dutch.

So a similar structure can use:

• hoe ..., hoe ...

The version with des te is perfectly correct, but it can sound a bit more formal or polished. Many learners will hear both patterns.

A useful thing to remember is:

• hoe ..., des te ... = very standard and correct
• hoe ..., hoe ... = also very common, often a bit more neutral in everyday use

They refer to two different locations in the sentence.

• bij de kruising tells you where it is getting busier
• in onze woonwijk tells you where the speaker cycles more carefully

So the sentence connects these ideas:

• when traffic or activity near the intersection increases,
• the speaker cycles more carefully in the residential neighborhood

Also, bij de kruising usually means at or near the intersection, not literally in the middle of it. That is why bij is natural here.

Yes, normally you separate these two linked parts with a comma:

• Hoe drukker het bij de kruising is, des te voorzichtiger fiets ik in onze woonwijk.

The comma marks the boundary between the first comparative clause and the second one. It makes the structure much clearer and is the standard way to write this kind of sentence.