Learn Hardcore Japanese: kono miti ha semai keredo, yoru ha kanari nigiyaka da. - This street is narrow, but it’s quite lively at night.

The first は marks the overall topic: この道は = “as for this road.”
The second は introduces a subtopic/contrast within that topic: 夜は = “as for nighttime (regarding this road).” It’s natural to “stack” topics like this: the main topic is the road; within that, you talk about nights. The subject of the second clause (the road/area) is left implicit because it’s already the topic.

Why is there no だ after 狭い, but 賑やか needs だ?

狭い is an i-adjective, which can be a predicate by itself and attaches directly to けれど: 狭いけれど.
賑やか is a na-adjective; when used predicatively, it needs the copula: 賑やかだ (plain) or 賑やかです (polite). Also note: before けれど, na-adjectives and nouns take だけれど (e.g., 静かだけれど), whereas i-adjectives take けれど.

How does けれど work here? How is it different from けど, けれども, が, and でも?

けど: most casual.
けれど: a bit more neutral/polite than けど.
けれども: more formal/emphatic.
が: formal/written connector meaning “but”; concise and neutral.
でも: sentence-initial “but/however,” starts a new sentence rather than linking within one. All can express contrast; choose based on formality and whether you want one sentence or two.

Can I say the sentence politely with です/ます?

Yes. For example:

この道は狭いですが、夜はかなり賑やかです。
この道は狭いですけれど、夜はかなり賑やかです。 Try to keep politeness consistent; avoid mixing plain and polite within the same sentence unless intentional.

Can I end a sentence with けど/けれど?

Yes, in conversation. Ending with けど/けれど can trail off, soften a statement, or invite a response. For example: この道は狭いけど… implies “it’s narrow, but… (there’s more).”

What nuance does かなり have compared with とても, けっこう, or すごく?

かなり: “quite/considerably”; relatively objective/neutral and fairly strong; common in both speech and writing.
とても: “very”; neutral and broad.
けっこう: “quite/pretty”; often “more than expected,” can sound modest or understated.
すごく: “very/really”; casual and emphatic. (Formal alternatives: 非常に, 相当.)

Could I say 夜に or 夜には instead of 夜は? What’s the difference?

夜は marks night as a (contrastive) topic: “as for nights.” Very natural with stative predicates like 賑やかだ.
夜には emphasizes “at night (in particular),” often contrasting with another time: 昼は静かだが、夜には賑やかだ.
夜に is a plain time marker. With stative descriptions like 賑やかだ, 夜に賑やかだ sounds odd; 夜に is better for events/actions (e.g., 夜に出発する). For change, use 夜になると賑やかになる.

What exactly does 賑やか mean? Is it positive? How is it different from うるさい?

賑やか: lively/bustling (lots of people, sound, activity); generally positive or neutral, used for places/events.
うるさい: noisy/annoying (unpleasant noise); negative. Related: 騒がしい (noisy/restless; negative-ish), 賑わう (to be bustling).

Is it natural to call a road 賑やか? What if I mean “busy with traffic”?

Yes, if you mean the street is lively with people/shops/entertainment. If you mean vehicle traffic, say:

交通量が多い (a lot of traffic)
車が多い (many cars)
混んでいる／渋滞している (crowded/there’s a traffic jam)

What’s the difference between 狭い and 小さい?

狭い: narrow/cramped (width/space). Natural for streets, corridors, rooms.
小さい: small (overall size). Not used for a road’s width. “This road is small” would be odd; use 狭い.

How would I say it’s quiet by day but lively at night using the same pattern?

Example: この道は昼は静かだけれど、夜はかなり賑やかだ。 This shows stacked topics (この道は, then 昼は/夜は) and contrast.

Could I rearrange the clauses?

Yes: 夜はかなり賑やかだけれど、この道は狭い。 The meaning stays, but the focus shifts to what comes first. The original foregrounds “narrow,” then contrasts with the lively nights.

Is 賑やか usually written in kanji? I’ve seen にぎやか too.

Both are fine. にぎやか (hiragana) is very common in everyday writing; 賑やか is also correct but the kanji 賑 is less frequently used.

Why is there a comma before 夜は? Is it required?

The comma marks a natural pause after the けれど clause. It’s stylistic, not strictly required. Without it is also fine: この道は狭いけれど夜はかなり賑やかだ。

Can I split it into two sentences with でも or start with でも like in English?

Yes:

Two sentences: この道は狭い。 でも、夜はかなり賑やかだ。
Starting with でも is natural; starting with けど at the very beginning is more colloquial and usually relies on prior context.