Breakdown of An der roten Ampel ist der Verkehr immer langsam.
sein
to be
immer
always
langsam
slow, slowly
an
at, on (vertical) / to (addressee) / of (in quantity/stock expressions)
Questions & Answers about An der roten Ampel ist der Verkehr immer langsam.
Why is the adjective spelled roten instead of just rote?
This is because it is in the dative case. The preposition an requires the dative case here to show a fixed location. Whenever an adjective comes after a definite article in the dative case, it always gets an -en ending, regardless of the noun's gender. So, rote becomes roten.
If Ampel is a feminine noun (die Ampel), why is the article der?
The preposition an is a "two-way" preposition. Because it describes a fixed location in this sentence (answering "where?"), it triggers the dative case. In the dative case, the feminine article die changes to der.
Why does the verb ist come before the subject der Verkehr?
German sentences follow the "verb second" rule. The entire phrase An der roten Ampel takes up the first position. To keep the verb in the second position, ist must come next, which pushes the subject der Verkehr to the third position.
Why do we use the preposition an here to say "at"?
In English, you stop "at" a traffic light, but German uses an, which usually means "on" or "at the border of". Standing right next to the intersection or traffic light requires an.