Speed – the human factor
By Hamish Mackie
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New areas of focus for speed limits are currently out for consultation and are underpinned by the Government’s emphasis on productivity and economic growth. It’s important that, as a country, we get the setting of speed limits right. We need to find the balance between ensuring that all road users are as safe as possible from harm, as well as ensuring that speed limits appear logical and make sense.
We have a significant road safety challenge in New Zealand. We were ranked 29th out of 35 OECD countries for road fatalities per 100,000 inhabitants in 2022, a step worse than Greece and a little better than Serbia. So how do we improve? We know that around two thirds of road crashes involving a death or serious injury occur because everyday people make a mistake, the remainder involving ‘reckless’ behaviour such as illegal blood alcohol, or excessive speeding. So while we rightly need to focus on those who deliberately operate outside of our legal system, there are huge gains to be made by accepting that everyday people just get it wrong sometimes and we need to design a system that, as far as possible, protects us all when mistakes are made.
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Global evidence shows that speed is an important ingredient in road safety solutions, along with safer roads, vehicles, and compliant road users. When it comes to speed limits, the takeaway is that we need the right speeds, in the right contexts, consistently across New Zealand. Let me explain why.
The right speeds
Basically, lower speed means less energy in a crash, and less harm. Or, the faster you go, the bigger the mess. For example, we know that the risk of a pedestrian fatality increases dramatically above 30 km/h, and on higher speed roads where there is a risk of head-on collisions, even the safest vehicles won’t prevent fatalities or very serious harm much above 70 km/h. This is why safe urban speed limits in busy pedestrian areas are globally considered to be 30 km/h, and rural speeds on undivided roads are 80 km/h.
We’ve also seen recent local examples that prove that safer speeds save lives. The evaluation of 880 km of Auckland roads that were subject to Phase 1 of the Safe Speeds Programme found a 30% reduction in fatalities (compared with a 9% increase in fatalities where speeds were not changed), and a relative reduction of 18.4% for all injuries. Likewise, an evaluation of rural speed limit reductions from 100 km/h to 80 or 90 km/h at appropriate locations in the Waikato have also led to reductions of deaths and serious injuries of around 30%.
We’ve also seen recent local examples that prove that safer speeds save lives. The evaluation of 880 km of Auckland roads that were subject to Phase 1 of the Safe Speeds Programme found a 30% reduction in fatalities (compared with a 9% increase in fatalities where speeds were not changed), and a relative reduction of 18.4% for all injuries. Likewise, an evaluation of rural speed limit reductions from 100 km/h to 80 or 90 km/h at appropriate locations in the Waikato have also led to reductions of deaths and serious injuries of around 30%.
On rural roads I do find it fascinating that as a society, we accept the risk of being separated from oncoming 100 km/h traffic by a 150mm painted line, when the slightest mistake can easily lead to death. Would we accept a 10th floor apartment balcony without a safety barrier? In a health and safety at work context, failure to take practicable steps to address such a risk would typically lead to prosecution.
However, day to day people don’t see these risks, and in reality we can’t expect everyone to be happy if we change to safer speed limits overnight. This is where we struggle, but we can be smart and reasonable about it, read on.
However, day to day people don’t see these risks, and in reality we can’t expect everyone to be happy if we change to safer speed limits overnight. This is where we struggle, but we can be smart and reasonable about it, read on.
The right contexts
If we want these safer speeds to be effective, it’s important they make sense to people – that they feel intuitive and credible. So if we are asking people to travel at 30 km/h, the surrounding road environment needs to reflect this. Mostly we drive on ‘auto-pilot’ and we need cues to help us automatically drive to the conditions. Having lower speed limits in places that look and feel much faster invites non-compliance and resentment. It’s very human to push back when things don’t seem fair or reasonable, or if we don’t understand why something has been done.
Most drivers already manage their speed to the situation. For example, where there are lots of people, shops, cafes, or busy school frontages, measured speeds are often a lot lower than the set speed limit. In these cases, a lower speed limit mostly just reinforces the safe speed choices people are already making and knocks off the top-end speeds. In some cases, drivers can be unaware of the risks and may make an unsafe speed choice if the speed limit isn’t set lower.
Often communities, schools, and businesses ask for safer speeds, as they see the risks on a daily basis. But we don’t hear much about these situations, people are just getting on with it, working with road authorities to make things better. Rather, we hear more about the controversial aspects of speed changes.
As well as putting the right speed limits in the right contexts, over the long-term we need to develop an overall ‘view’ of the world for what normal is. With helpful national level conversations and sensible local implementation, we can all learn what safe and sensible speeds are. On Swedish roads, you will never see an undivided road at 100 km/h, and over time, depending our on our understanding, conversations, and actions, this could also be normal for New Zealand.
But firstly focussing lower speed limits on the areas and streets that really make sense to us all, before taking on more difficult areas over time is a good way to improve both safety and buy-in. School communities, town centres, and other areas where people naturally want to slow down are the places to start. Rural roads that are winding, narrow, or constantly changing are naturally places for slower speeds we would all buy into.
Most drivers already manage their speed to the situation. For example, where there are lots of people, shops, cafes, or busy school frontages, measured speeds are often a lot lower than the set speed limit. In these cases, a lower speed limit mostly just reinforces the safe speed choices people are already making and knocks off the top-end speeds. In some cases, drivers can be unaware of the risks and may make an unsafe speed choice if the speed limit isn’t set lower.
Often communities, schools, and businesses ask for safer speeds, as they see the risks on a daily basis. But we don’t hear much about these situations, people are just getting on with it, working with road authorities to make things better. Rather, we hear more about the controversial aspects of speed changes.
As well as putting the right speed limits in the right contexts, over the long-term we need to develop an overall ‘view’ of the world for what normal is. With helpful national level conversations and sensible local implementation, we can all learn what safe and sensible speeds are. On Swedish roads, you will never see an undivided road at 100 km/h, and over time, depending our on our understanding, conversations, and actions, this could also be normal for New Zealand.
But firstly focussing lower speed limits on the areas and streets that really make sense to us all, before taking on more difficult areas over time is a good way to improve both safety and buy-in. School communities, town centres, and other areas where people naturally want to slow down are the places to start. Rural roads that are winding, narrow, or constantly changing are naturally places for slower speeds we would all buy into.
Consistently across New Zealand
Our auto-pilot driving behaviours are developed from being exposed repeatedly to the same cues over and over. This is how we learn any advanced skill. So if our goal is to have the right speeds in the right contexts, we need to apply this consistently across New Zealand. We are a mobile society, and we don’t only drive in our neighbourhood. We drive across town and around the country, and so the way different speed limits are used should be the same in Auckland as they are in Hamilton.
This is why we have the same signs and road markings, applied in the same way, around the country. The red circle around a speed limit sign is incredibly powerful and we learn to associate this with a legal speed limit, in the same way the red octagonal shape of a stop sign is unmistakable.
With repeated exposure we get a strong understanding of how to safely operate on the road, and the same goes for speed limits. This suggests a national and consistent approach, with communities helping to get it right locally. This would also save us a lot of money!
This is why we have the same signs and road markings, applied in the same way, around the country. The red circle around a speed limit sign is incredibly powerful and we learn to associate this with a legal speed limit, in the same way the red octagonal shape of a stop sign is unmistakable.
With repeated exposure we get a strong understanding of how to safely operate on the road, and the same goes for speed limits. This suggests a national and consistent approach, with communities helping to get it right locally. This would also save us a lot of money!
What about productivity?
The safety/productivity debate is a separate discussion, but there are a range of important concepts that need to be factored in, thinking about how people behave and what we value.
Some include:
Some include:
- Actual travel time, and how it is mostly affected by intersections and congestion in urban locations, as opposed to speed limits.
- How we perceive and value travel time – we tend to think that we’ll get where we are going faster when speed limits increase, but research shows that there is little difference most of the time.
- What really matters to people, a few seconds delay, or large and inconsistent delays due to congestion or a crash? We tend to value predictability over small travel time increases.
- Lower speed limits in the right places are also important in encouraging pedestrians and cyclists, leading to health, climate benefits, and shopping centres that just feel nicer. This is good for business and helps to reduce healthcare costs.
What’s the way forward?
There’s obviously a lot of ‘devil in the detail’, but it’s important we firstly understand the science, and work towards a unified set of principles based on the science and what we value as a country. The evidence points to::
- The right speeds: speed limits that reflect survivability and risk.
- In the right contexts: speed limits that make sense to everyday people in different contexts, understanding we are on a journey.
- Consistently across New Zealand: A unified approach across the country so that over time everyday people intuitively know what to expect in different circumstances, and behave accordingly.
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Dr Hamish Mackie is co-Director of Mackie Research and is a certified Human Factors specialist (how people work and how they respond to the world around them). Hamish has led a range of road safety and other transport projects over the past 20 years.
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