A speed limit of 30km per hour is in place in the eastern suburbs of Christchurch.
The restriction is to prevent further deterioration of the roads and to enable repairs to take place.
Civil Defence says the lower speed limit applies from New Brighton across to Dallington and Avonside, and as far south as Sumner.
Police Inspector Al Stewart says speeding vehicles are an extra stress for residents in parts of the city.
Civil Defence says there are 38,000 road defects that need repairs due to the earthquake, but contractors have repaired almost all the damage to arterial roads.