The cut from 50km/h to 30km/h would be to reduce the risk of pedestrian fatalities, according to a report from the University of NSW.

The study recommended lowering the limit to 40km/h or 30km/h in high pedestrian areas, such as city CBDs, suburban shopping strips and school zones.

“Pedestrians struck in vehicle crashes are the largest group of traffic fatalities worldwide – and excessive speed is the biggest factor in such crashes,” said UNSW Professor Jake Olivier.

“Even an impact speed of as low as around 30km/h is equivalent to what you would experience if you fell off the roof of your house.”

An analysis of crash data from six countries found that risk of a fatality reaches 5 per cent at an estimated impact speed of 28km/h, 10 per cent at 36km/h, 50 per cent at 57km/h, 75 per cent at 67km/h and 90 per cent at 78km/h.

“So, for example, if a pedestrian gets hit by a vehicle at 30km/h impact speed, the average risk of death is at 6 per cent  – but when the impact speed increases by 1km/h, the odds of a pedestrian fatality increases on average by 11 per cent,” Professor Olivier said.

According to the Centre for Road Safety, there are areas in NSW where the speed limit is below 50km/h.

There are already 188 40km/h High Pedestrian Activity Areas (HPAAs) in NSW, including several in the Illawarra.

There also speed zones in the Sydney CBD that fall as low as 20km/h and even 10km/h in some areas.

Centre for Road Safety executive director Bernard Carlon said 40km/h speed zones were working.

“An evaluation of 40km/h high pedestrian activity areas in NSW found they were effective in improving safety, with a 33 per cent reduction in crashes resulting in serious injuries and deaths between 2005 and 2015,” Mr Carlon said.

“The benefits were observed not only for pedestrians, but for all road users.”