Almost every residential street in Portsmouth has become a 20mph zone, with the rest to follow by the spring.
Only one more section of the city remains to be covered by the low-speed scheme.
Portsmouth City Council is the first in Britain to make almost all its residential roads 20mph.
Its plan, which is funded by the Government, has attracted national attention and stimulated interest from other councils.
Norwich is already exploring a similar scheme.
Cllr Alex Bentley, Portsmouth council's executive member for traffic and transportation, said: "Most of our residential streets are just not suitable for speeds of more than 20mph, and we're sending a message to the reckless minority of drivers that they must drive safely."
While all residential roads will eventually be covered by the 20mph limit, most main routes - such as London Road, Northern Parade, Mile End Road, Eastern Road and the seafront - will keep their current limits.