Road safety campaigners say speed limit should be lowered to 30km/h in certain areas

A road safety campaigner says the speed limit should be 30km/h in some areas to reduce the risk of serious injuries from crashes.

Auckland Transport is currently investigating a bylaw to reduce the speed limit in high-risk areas to protect cyclists and pedestrians.

It's planned most of Glen Eden town centre will go down to the lower limit and four high risk intersections and three high-risk routes have been identified in the Kaipātiki area.

Some residents are in support of the bylaw, but others have reservations.

"There is an old adage that no law without popular support is enforceable," Bayview's Christopher Coulter wrote on Neighbourly.

"I never speed intentionally but I for one will not drive at 40kmh unless it is for a specific purpose like school zones."

Caroline Perry from road safety charity Brake New Zealand told The AM Show while speed may not be the cause of all crashes, it is always a deciding factor.

"Speed is a factor in all crashes in terms of the outcome of that crash," she said.

"So whether it's a cause or not, it's going to determine whether you're injured in a crash, whether you're killed in a crash."

Ms Perry said our children, elderly, and people with disabilities are at most risk when they're out on the street and should be protected.

"We want to protect them, so that means having our residential areas, our communities, shopping centres at 30km/h so that they can get out and about safely and [it's also] encouraging more of us to walk and cycle too."