This sign and others like it have been created and posted by students of Kaarli Kool (school) in its surrounding laneways and parking lots: Do not drive fast, it's dangerous! DRIVE SLOWLY! Kihutama is to drive fast. Its other meaning is to urge on or encourage, as in tagant kihutama / takka kihutama ("kihuta from behind"). Kihutus/töö is the act of promoting or propagating ("kihutus-work"). Vaikselt literally means "quietly", but also slowly in the given context. You could also say "Sõida tasa". Tasa / tasaselt means quietly, evenly, gently. If someone says "(Ole) tasa!" or simply TASA! it means "Be quiet".
Photo and text: Riina Kindlam, Tallinn.