Situation: A rented flat with a busy street right in front of it. The bed room faces towards the street with a window front. As the flat is rented I can not build something permanently like new windows or a wall. I already thougt about styrofoam plates, other foam or heavy curtains but don't know what is usable.
According to a municpial computer model the noise is between 55-75 dbA in 4m height from the ground. The flat is like 10-15m from the ground.
How could I reduce the noise from the street?
Edit 2: The noise is mostly a problem during bedtime as it disturbs the sleep. Foam earplugs are not a solution for everyone due to medical reasons.