40km/h speed limits for Sydney's CBD

Travelling through parts of central Sydney will be even slower from the end of September, with a maximum 40km/h speed limit set to be imposed by Christmas.

From September 27 the government will roll out the measure, which NSW Roads Minister Duncan Gay says "further improve pedestrian safety."

"Considering a vehicle that hits a pedestrian at 50km/h is twice as likely to cause a fatality as the same vehicle travelling at 40km/h, this speed limit change will deliver significant safety benefits," he said in a statement.

The 40km/h limit will be imposed on streets between Castlereagh Street, Kent Street and Hay Street.

While the measure is targeting drivers, Mr Gay warned pedestrians to pay attention when near busy roads.