Learn Hardcore Japanese: kuruma yori tikatetu no hou ga zutto hayai desu.

It’s a postposition meaning “than/compared to.” It attaches to the thing you’re comparing against. In the sentence, 車より means “than cars.” Common patterns:

B は A より形容詞 (B is adjective-er than A)
A より B のほうが形容詞 (Compared to A, the B one is adjective-er)

What does のほう mean? Why is there a の after 地下鉄?

方(ほう) literally means “side/option.” X のほう means “the X side/the X one.” In comparisons it picks out the option that has more of the quality: 地下鉄のほう = “the subway one.”

Do I have to use のほうが? Can I just say 地下鉄が車より速いです?

You don’t have to use it. Both are fine:

地下鉄は車より速いです (very common)
車より地下鉄が速いです (grammatical but a bit abrupt)
車より地下鉄のほうが速いです adds clarity that you’re choosing the subway option.

Why is が used after のほう? Could I use は instead?

Yes. が marks the subject and fits answers to “Which is faster?”:

地下鉄のほうが速いです。 は topicalizes and invites contrast:
地下鉄のほうは速いですが、料金は高いです。 Both are correct; choose based on nuance.

What does ずっと add? Can I omit it?

ずっと intensifies: “by far/much.” Without it: “The subway is faster.” With it: “The subway is much faster.” You can omit it if you don’t need emphasis.

What’s the difference between ずっと and もっと?

Both can modify adjectives in comparisons: A は B よりずっと/もっと速い.

ずっと = “by far,” a neutral, strong intensifier.
もっと = “even more,” often used when urging an increase or emphasizing “more than that.” For simple factual comparisons, ずっと is very natural; もっと also works.

Where should ずっと go in the sentence?

Right before the adjective: ずっと速い. You can place it on either side of the より-phrase:

車より地下鉄のほうがずっと速いです。
地下鉄のほうが車よりずっと速いです。

Which hayai is correct here: 速い or 早い?

Use 速い for speed (fast). Use 早い for time (early). A fast train = 速い電車; getting up early = 早く起きる. For this sentence, 速い is best.

How do I pronounce the sentence?

Romaji: kuruma yori chikatetsu no hou ga zutto hayai desu. Notes: ほう has a long vowel (hoo). ずっと has a doubled t sound. The “u” in です is often devoiced, so it sounds like “des.”

Why are there spaces between the words here?

They’re for learners. Normal Japanese is written without spaces: 車より地下鉄のほうがずっと速いです。

Can I change the order and start with the subway?

Yes:

地下鉄は車よりずっと速いです。
地下鉄のほうが車よりずっと速いです。 Same meaning; different focus/emphasis.

How do I say “not as fast as”?

Use ほど with a negative:

車は地下鉄ほど速くありません。 (Cars are not as fast as the subway.) Plain negative: 速くない.

How do I compare actions, like going by car vs. subway?

Put verb phrases before より/のほう:

車で行くより地下鉄で行くほうがずっと速いです。 (Going by subway is much faster than going by car.)

Why is です used after an i-adjective? Is 速いだ okay?

い-adjectives don’t need だ. 速い is a complete predicate. 速いです just makes it polite. Never say 速いだ.

Does 車 here mean “a car” or “cars in general”?

Japanese nouns don’t mark singular/plural. 車より can mean “than a car,” “than cars (in general),” or even “than going by car,” depending on context.

How would I ask “Which is faster, the car or the subway?”

車と地下鉄とでは、どちらのほうが速いですか。 Answer with: 地下鉄のほうが速いです。

Is 地下鉄の方 the same as 地下鉄のほう? Which should I write?

Yes, same word. 方 is the kanji; ほう is the kana. Both are common; no meaning difference. It’s always read ほう here (not かた).

Can I say 車よりは地下鉄のほうが…?

Yes. よりは adds a contrastive, slightly hedging nuance: “at least compared with cars, the subway is…”. It’s useful when softening claims or contrasting with something just mentioned.