International report recommends 30km/h in NZ cities, 70km/h on rural roads

New Zealand could see a dramatic shift in speed limits if a new recommendation of 70km/h on rural roads and 30km/h in built up areas is implemented.

A report by the International Transport Forum in Paris has recommended that in order to reduce the risk of head-on collisions, rural roads without a median barrier should have a speed limit of 70km/h.

The forum is made up of 59 member countries including New Zealand. 

If implemented, this would mean almost all of New Zealand's roading network would have to have its speed limits reduced, including state highways.

The forum recommended a speed limit of 30km/h in built up areas that have vulnerable road users like cyclists and pedestrians and 50km/h in other areas that have intersections and are at high risk of side collisions. 

A 50km/h limit was also recommended for most urban areas.

"To reduce road trauma, governments need to take actions that will reduce the speed on roads as well as speed differences between vehicles sharing the same road," the report says. 

The forum studied crash cases from ten countries to find the relationship between vehicle speed and crash risks. 

The report says studies showed that each one percent increase in the average vehicle speed resulted in a two percent increase in the frequency of injury crashes, a three percent increase in severe crash frequency and a four percent increase in fatal crash frequency. 

"Thus, reducing speed by a few km/h can greatly reduce the risks of and severity of crashes. Lower driving speeds also benefit quality of life, especially in urban areas as the reduction of speed mitigates air pollution, greenhouse gas emissions, fuel consumption and noise," the report states. 

The report also recommended improving infrastructure and automatic speed control systems.