Wir warten an der Straße, bis die Ampel grün wird.

Not usually. An der Straße means at the street, by the roadside, or next to the street.

A native English speaker might expect on the street, but in German:

• auf der Straße = on the street / in the street
• an der Straße = at the side of the street / by the street

So this sentence suggests standing or waiting near the road, not out in the middle of it.

Because an is followed by the dative here.

The noun is:

• die Straße = the street

But after an with a location meaning, German uses the dative:

• an der Straße = at the street / by the street

So the article changes like this:

• nominative: die Straße
• dative: der Straße

An is a two-way preposition. That means it can take either:

• accusative for movement toward a destination
• dative for location

Here, the sentence describes a location, not movement:

• Wir warten an der Straße. = We are waiting by the street.

If it were about moving toward the street, you could get accusative:

• Wir gehen an die Straße. = We go to the street / toward the street.

So the dative is used because the people are already there, waiting.

Good question. Warten auf means to wait for someone or something.

Examples:

• Ich warte auf den Bus. = I’m waiting for the bus.
• Sie warten auf ihren Freund. = They are waiting for their friend.

But in your sentence, warten is being used without a direct object. It just means to wait, and then the sentence adds:

• where they are waiting: an der Straße
• until when they are waiting: bis die Ampel grün wird

So:

• Wir warten an der Straße ... = We are waiting by the street ...
• not Wir warten auf der Straße — that would sound wrong here

Bis means until.

It introduces the point in time when the waiting ends:

• Wir warten ..., bis die Ampel grün wird.
• We wait ..., until the traffic light turns green.

So the structure is:

• main clause: Wir warten an der Straße
• subordinate clause with bis: bis die Ampel grün wird

Because bis introduces a subordinate clause, and in German subordinate clauses, the conjugated verb usually goes to the end.

Compare:

• main clause: Die Ampel wird grün.
• subordinate clause: ..., bis die Ampel grün wird.

This is a very common German pattern:

• weil er müde ist
• dass sie kommt
• wenn wir Zeit haben
• bis die Ampel grün wird

So the verb-final position is normal here.

Because grün wird means becomes green or turns green, and that matches the idea of a traffic light changing.

• Die Ampel ist grün. = The traffic light is green.
• Die Ampel wird grün. = The traffic light is turning green / becoming green.

In English, we often say until the light is green, but German very naturally uses werden for this change of state.

Because grün is a predicate adjective here, not an adjective directly before a noun.

In German, predicate adjectives do not take endings:

• Die Ampel ist grün.
• Die Ampel wird grün.

But if the adjective comes before a noun, then it does take an ending:

• die grüne Ampel = the green traffic light

So:

• die Ampel grün wird → no adjective ending
• die grüne Ampel → adjective ending needed

Because German normally uses a comma before a subordinate clause.

Since bis die Ampel grün wird is a subordinate clause, it must be separated by a comma:

• Wir warten an der Straße, bis die Ampel grün wird.

This is much stricter in German than in English, where commas are sometimes more flexible.

Die Ampel means traffic light.

It is a feminine noun:

• nominative: die Ampel
• accusative: die Ampel
• dative: der Ampel
• genitive: der Ampel

In everyday German, Ampel by itself usually means a road traffic light.

Yes, that is possible, but it is slightly different in feel.

• bis die Ampel grün wird = until the light turns green
• bis die Ampel grün ist = until the light is green

Both are understandable, but grün wird focuses on the change, which is very natural for traffic lights. In many situations, German speakers would prefer wird here.

In standard German, the subject is usually stated, so Wir is needed.

• Wir warten ... = We are waiting ...

German verb endings do give some information, but not enough to regularly leave out the subject in normal sentences. So unlike in Spanish or Italian, you generally do not drop subject pronouns in standard German.

Not exactly.

• Straße = street, road
• Weg = way, path, route, lane, walkway, depending on context

In this sentence, Straße is the normal word because it refers to an actual road/street by which the people are waiting.