Reducing the speed limit from 50 to 30 kilometres per hour reduces road noise as much as if there were about 40 to 50 per cent fewer vehicles on the road, transport administration spokesman Jan Thomsen told the newspaper. "This makes a speed reduction an effective measure to reduce motor vehicle noise even on main roads." The goal of expanding speed 30 zones is anchored in the coalition agreement of the SPD, the Greens and the Left. However, it is not legally possible to introduce 30 km/h speed limits throughout Germany.