The Australasian College of Road Safety (ACRS) is calling on the New Zealand Government to implement a 90 km/h speed limit on undivided rural roads that presently have a 100 km/h speed limit, as a practical measure to reduce road trauma and reduce fuel use.
ACRS CEO, Dr Ingrid Johnston said strong evidence shows that modest reductions in travel speed can deliver significant safety and economic benefits.
“Research indicates that optimal cruising speeds on rural roads are closer to 75 km/h when considering safety, fuel use, and emissions. While that may not be practical across the network, a 90 km/h speed limit is a realistic and effective step,” Dr Johnston said.
Importantly, a 90 km/h speed limit trial would have no impact on the heavy vehicle industry. Vehicles with a gross vehicle mass above 3,500 kg are already subject to a speed limit of 90 km/h, even on roads where the speed limit is posted as 100 km/h or 110 km/h.
Historical and recent evidence supports the proposal. When rural road speed limits in New Zealand were reduced during the 1970s fuel crisis, road deaths declined, before rising again when speed limits were increased in the 1980s. More recently, a speed limit reduction from 100 km/h to 90 km/h on State Highway 2 near Maramarua resulted in a 35% reduction in people killed and seriously injured.
Lower operating speeds also improve road safety outcomes by reducing crash likelihood and severity. The latest Austroads report, Review of Speed Management Evidence and Guidance1, confirms that even small reductions in speed lead to significant reductions in road trauma, alongside benefits such as lower fuel consumption and largely negligible impacts on travel times.
“Many drivers already travel at around 90 km/h on undivided rural roads according to travel surveys, particularly where conditions are challenging. A 90 km/h speed limit would formalise safer speeds, reduce the proportion of motorists travelling too fast for the conditions, and create a more forgiving road environment,” Dr Johnston said.
Aerodynamic drag increases rapidly for relatively small increments in travel speed; particularly at higher speeds. International evidence shows2 that lower speeds reduce fuel consumption and emissions. For a 300 km typical open road route, the savings for all vehicles on just that one route are estimated at around $50-70K per day. So the savings across New Zealand are potentially enormous.
For undivided roads where the existing speed limit is 100km/h, the ACRS recommends implementing a 90 km/h speed limit, with monitoring to evaluate impacts on safety, fuel consumption and community acceptance.
“This is a pragmatic, low-cost intervention that could deliver immediate benefits. Evaluation would allow New Zealand to assess the outcomes based on evidence, to ensure the new speed limit is working as intended” Dr Johnston said.
Source:
- Austroads (2025), Review of Speed Management Evidence and Guidance: https://austroads.gov.au/publications/road-safety/ap-t385-25/media/AP-T385-25_Review_of_Speed_Management_Evidence_and_Guidance.pdf
- IEA, Road transport fuels (https://www.iea.org/reports/sheltering-from-oil-shocks/road-transport-fuels)