No rule for this one
No ending or word group predicts the article of Ampel. Learn it as a pair and say it out loud: die Ampel.
die Ampel
It's die Ampel. Ampel is feminine, plural die Ampeln.
An der Ampel gehen Sie links.
At the traffic light go left.
No ending or word group predicts the article of Ampel. Learn it as a pair and say it out loud: die Ampel.