The centre of Cambridge is to become a 20mph zone for drivers from this week.
Road signs for the year-long trial scheme have been going up in streets bounded by the inner ring road and the River Cam.
It is hoped the scheme will reduce accidents by protecting children, cyclists and pedestrians, and encourage more people to walk and cycle.
Some streets are already a 20mph zone, but now the whole area will be subject to the limit.
Cambridgeshire county councillor Mac McGuire, said: "By making the area safer it is more likely people will want to walk or cycle and therefore reduce congestion and improve the environment."