Speeding towards danger: the concerns and consequences of increasing speed limits on our roads

The trend of reducing speed limits in urban areas and on selected state highways in New Zealand reflects a growing consensus among local authorities and the New Zealand Transport Agency (Waka Kotahi) regarding the importance of road safety. This shift towards lower speed limits is not merely a random decision but a strategic move aligned with the Road to Zero strategy, which aims to eliminate road fatalities and serious injuries. However, the current coalition Government plans to reverse many of the speed limit reductions introduced by the previous Labour Government. The proposed changes would see many state highways reverting to 100km/h from 80, and local roads returning to 50km/h from 30, while introducing new highways designed for 110km/h speeds.

The prospect of sweeping reversals in speed limit reductions has sparked concerns regarding impacts on road safety. In a proactive move, the New Zealand Trauma Committee of the Royal Australasian College of Surgeons reached out to the ministers of transport, health and ACC last year, urging them to proceed with caution and not rush into changes that, in some respects, even go beyond the National Party’s election promise to scrap lower speed limits only “where it is safe to do so”.¹ This plea underscores the critical importance of prioritising safety considerations in any decision related to speed limit adjustments.

The ministers of ACC and health remained silent in response, while the minister of transport issued a brief reply emphasising the importance of keeping New Zealand’s transportation system in motion. But the implied time savings for people driving are uncertain, as we discuss further below, in contrast to the high likelihood of increases in road deaths and serious injuries, as well as other adverse health and environmental impacts. It seems that increasing maximum driving speeds has been prioritised over all other considerations, which does not reflect the balance needed for responsible decision-making about our transport system. And it flies in the face of best practice in road safety based on global evidence.²

One of the most pressing concerns is the inevitable increase in deaths and serious injuries that would result from higher speed limits. Studies have shown that higher speeds directly correlate with a greater risk of crashes and more severe outcomes for those involved.³ Consequently, there is little doubt that increasing maximum speeds will lead to more lives being lost on our roads. Despite progress in transport designs, high severity trauma in New Zealand is dominated by road traffic injuries, as evident in a recent 10-year review.⁴

The data and evidence surrounding speed limit changes in urban areas and state highways provide a compelling argument for the effectiveness of lower speed limits in enhancing road safety.

International studies conducted in cities like London and Edinburgh have demonstrated the positive impact of 30km/h zones on reducing injuries.^5,6 These studies revealed a 30–40% reduction in injuries within these zones, with subsequent reviews in European cities indicating a 40% reduction in injuries across various urban areas.⁷ The implementation of 30km/h zones not only leads to a significant drop in injuries, but also contributes to additional benefits such as lower emissions, reduced noise levels and decreased fuel consumption, with no indication of increased congestion.⁷

The historical examples of speed limit changes in the United States of America (USA) and New Zealand provide valuable insights into the impact of speed on road safety outcomes. In the USA, the repeal of federal speed limit controls on interstates in 1995 led to an increase in road fatalities on these highways from 4–9%. This stark contrast with the 16% reduction in road fatalities following the federal government’s decision to lower interstate speed limits in 1974 underscores the critical role that speed limits play in ensuring road safety.⁸ Similarly, New Zealand’s decision to reduce its open road speed limit from 60mph to 50mph (80km/h) in 1973 resulted in a significant decline in road fatalities by 37%, demonstrating the positive correlation between lower speed limits and improved road safety outcomes.⁹

The relationship between traffic speeds and perceived traffic safety is a crucial factor influencing the choices of pedestrians and cyclists. Studies have shown that perceived traffic danger can deter individuals from walking and cycling, highlighting the importance of traffic calming measures to create safer and more inviting environments for non-motorised road users. Shifting short neighbourhood trips from driving to walking and cycling in New Zealand would lead to substantial health gains and healthcare savings.¹⁰

Proponents of raising speed limits argue that it will result in time savings and boost economic productivity. However, the purported benefits of time savings are often overstated. In cities, travel times are affected not only by speed limits, but by congestion from the number of other cars on the road and the need to stop at traffic lights and other intersections. Smoother traffic flow from lower speed limits may have travel time benefits.¹⁰ On the contrary, the health impacts of raising speed limits are likely to be significant and far-reaching. The costs associated with the potential increase in deaths, injuries and negative health outcomes are likely to far outweigh any perceived benefits. The speed limit reductions implemented in recent years have not only saved lives, they have been well supported by the public, with over 70% of school leaders supporting permanent safe speed zones around schools.¹¹

Furthermore, the adverse impacts of the proposed policy shifts in road speeds are likely to be unfairly distributed. It is well established that pedestrian and road injury risks are disproportionately borne by tamariki Māori and Pacific children, older people, disabled people, rural communities and residents of socio-economically disadvantaged urban neighbourhoods.¹² Many of these groups have lower access to cars but are more likely to be injured by them. They are also more likely to face severe and disabling consequences, with higher out-of-pocket expenses and many unmet needs alongside barriers to accessing care. Therefore, the proposed policies are most likely to accentuate risks to personal safety and opportunities for active travel in already underserved communities. To prioritise opportunities for motorists to drive at pace ahead of conditions that protect opportunities for active travel and safety of non-motorists is inherently unjust and unethical.

These risks compound the economic, resource and workforce demands placed on healthcare systems to mitigate the inequitable access to safe and inclusive transport systems, a fundamental determinant of health. Acknowledging the precautionary principle in public health, proposed policy shifts require a thorough pre-emptive analysis that takes account of our commitments to Te Tiriti o Waitangi and health equity. 

In conclusion, the current proposal to raise speed limits on our roads is hard to defend given what we know about the probable consequences. The likely outcome of increased deaths and injuries, worsened air quality and heightened health impacts are too significant to ignore. The state has a responsibility to assure collective health interests and avoid third-party harm, particularly to children and other vulnerable road users. It is imperative that we prioritise road safety, environmental sustainability and public health in any discussions or decisions regarding speed limits on our roadways.