novice driver mark; new driver sticker
Colloquial term for the green-and-yellow V-shaped symbol that new drivers in Japan must display on their vehicle for one year after obtaining a license. Also called 初心者マーク or 初心運転者標識 in official contexts.
I just got my license, so I have a novice driver mark on my car.
Other drivers are required to show consideration for cars displaying the novice driver mark.