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Myth: Going a few kilometres faster or slower doesn’t make any difference to safety

Actually, it does. Speed is the difference between a correctable mistake and a fatal error. Every extra km/h increases the likelihood of someone having a crash. Regardless of what causes a crash, speed always plays a part.

A large and credible body of international research indicates reducing speeds has a direct impact on reducing deaths and injuries. The most recent study from the International Transport Forum (2018) estimates that for every 5km/h reduction in average speeds, there is a 28 percent reduction in fatal crashes and a 26 percent reduction in serious injury crashes. The risk of an injury crash approximately doubles between 80km/h and 100km/h.

International Transport Forum study(external link) (2018)

When a vehicle crashes, it undergoes a rapid change of speed, but the people in the vehicle keep moving at the vehicle’s previous speed until stopped. The faster the speed at which the human body must absorb the energy released in the crash, the greater the severity of the resulting injury.

Your speed dictates what happens if you hit another vehicle or person and whether you have time to react and avoid a collision. For example, if someone steps out in front of you and you take one second to react:

  • Driving at 50km/h, you need at least 27m to stop
  • Driving at 60km/h, you need at least 36m to stop.

The probability that the pedestrian will die or be seriously injured increases rapidly with relatively small increases in speed. The risk of a pedestrian being killed or seriously injured if struck by a car roughly doubles between an impact speed of 30km/h and 40km/h and doubles again between 40km/h and 50km/h.

For more vulnerable pedestrians, such as a child or an elderly person, the risks are particularly high.

“Lower speeds are not a panacea for all sins. But, at a time when our road toll is rising, the one key tool that we haven't picked up from overseas yet is to introduce lower speeds more widely on our roads.” Dr Glen Koorey, 2015.

The video below shows a reconstructed crash advertisement by the Traffic Accident Compensation Victoria and demonstrates what happens if you drop your speed from 65km/hr to 60km/hr in an accident.

View road crash statistics on the Ministry of Transport’s website(external link)

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Myth: Speed isn’t a major cause of road crashes

According to Police reports, travelling too fast for the conditions was a contributing factor in about a third of all fatal crashes, and it affects the impact of every crash. Even good drivers can hurt others if they travel at the wrong speed for the road and conditions.

We all make mistakes sometimes. Speeding is one risk that good drivers can minimise. Speed contributes to the severity of the impact when a collision does occur. For car occupants in a crash with an impact speed of 80km/h, the likelihood of death is 20 times what it would have been at an impact speed of 40km/h.

According to MegaMaps analysis, half of all injury crashes occurred on roads and streets where the speed limit was higher than the recommended safe and appropriate speed.

 “But it's more than just about safety. Lower speed limits also encourage more people to walk and cycle (due to the calmer environment provided), with all the health and environmental benefits this brings. It also makes for more pleasant places to live, work and play, resulting in economic benefits from the improved amenity (eg. higher property values, more local shopping).”Dr Glen Koorey, 2015

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Myth: Slowing down will mean it takes a lot longer to get anywhere

Many people over-estimate the time they would lose if they drove at a slower speed.

When you factor in things like traffic lights and congestion, travel times don’t vary as much as you think.  A study, commissioned by Waka Kotahi NZ Transport Agency, tracked travel times along six different routes spread between several major towns and cities and looked at both long journeys and shorter urban trips. It found that when driving at the maximum posted speed limit wherever possible, drivers arrived at their destination as little as 1.08 minutes quicker than when they drove 10km/h slower.

Trips reducing the maximum speed from 100km/h to 80km/h on a 10km length of road showed travel time increases ranged from 30–48 seconds. For local trips reducing the maximum speed from 50km/h to 40km/h showed travel time increases ranged from 11–42 seconds difference.

Trip type Distance Maximum speed (time) before Maximum speed (time) after

Open road travel


100km/hr (06:00)

80km/hr (06:30–06:48)
30–48 seconds difference

Local road trips


50km/hr (04:48)

40km/hr (05:09–05:30)
11–42 seconds difference

If the maximum speed limit around a typical town is 50km/h, your average journey speed is between 26km/h and 33 km/h. Safe and appropriate speeds result in significant fuel savings.

Increasing safety might also improve journey times. Many of us have been on our roads when there has been a serious crash. These traumatic crashes cause significant physical and emotional harm and they also create additional economic costs and lost productivity from the resulting traffic jams while crashes are being investigated.

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Myth: Lower speed limits will harm the economy, especially for moving freight

A research project commissioned by Waka Kotahi [PDF, 1.4 MB] found a drop in maximum speed travelled along certain routes from 100km/h to 80km/h increased travel times by around 10 percent and reduced fuel use by about 15 percent.

So while there would be small increases in travel times with lower speed limits, these pale into insignificance when compared with the potential to save lives and prevent serious injuries.

An earlier Waka Kotahi unpublished report studied the combined impacts of changes in mean speeds to road safety risk, travel times and fuel use for heavy vehicles. It concluded that the ‘optimum’ speed for heavy vehicles taking these three factors into account would be around 80km/h (Max Cameron, 2012)

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Myth: Modern cars are safer and better, so there’s no need for us to drive slower

Cars may have evolved to go faster, but humans haven’t; our bodies feel the force of a crash the same way they did when the first car was invented.

While modern cars have better safety equipment that can help protect us, New Zealand’s vehicle fleet is relatively old and unsafe, especially when compared to other countries like Australia and the UK. Half the cars on New Zealand’s road lack even basic safety features, like electronic stability control or side airbags.

New Zealand roads are often unforgiving and leave no room for error. Many do not have median barriers to prevent head-on crashes, or roadside protection to stop people hitting trees and power poles. Even the best technology won’t stop another vehicle crashing into you or protect you from impact with a roadside object.

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Myth: It’s slow drivers who cause crashes, because they cause others to overtake

Travelling too fast for the conditions contributed to the cause of about a third of all fatal crashes. On the other hand, slow driving is not significantly implicated as a cause in our poor crash statistics.

The posted speed limit is a maximum not a target. Drivers are expected to adjust their travelling speeds depending on the weather conditions and road environment and show patience.

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Myth: The speed limits in NZ are low compared to other countries already, so it’s ridiculous to make them even lower

Our roads are unique. They are windy, hilly and often single lane so can be challenging and demanding to drive, and the consequences of small errors can be fatal. And yet we have a default speed limit of 100km/h on most open roads, regardless of how safe they might be to drive.

Many countries we compare ourselves with have a default speed limit on the open road that is lower than ours. It’s only on highest quality motorways in some of those countries that speed limits are higher.

We need to help drivers choose the right speed for the road. We also need to reduce the risk on the road by improving the roads or lowering speed limits.

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Myth: The problem isn’t speeding – it’s bad drivers not driving to the conditions or the rules

Improving everyone’s driving skills, and their ability to read the road, would have a positive impact on the speeds people travel and the harm done on our roads. Speed is one risk that good drivers can minimise.

Drivers should consider the appropriate speed for the road, every time they drive. While poor driving behaviour has resulted in crashes, more are a result of mistakes and even the most experienced “perfect” driver among us drops the ball sometimes. Whether late for a meeting or work, or late dropping the kids off/picking up from school, everyday pressures can influence our driving behaviour and result in us making driving errors. These mistakes shouldn’t result in loss of life or serious injury and the speed you are driving by far has the greatest influence on the severity of a crash, and it could be the difference between life, death or serious injury.

In fact, it has been found that: if all road users complied totally with all road rules, fatalities would fall by around 50 percent and injuries by 30 percent, therefore around 50 percent of fatalities and 70 percent of injuries would remain (Elvik R, 1997.)

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Myth: It’s the road not the speed limit that needs changing

New Zealand’s roads are not as safe as those in other countries. Our road network is comparatively long and stringy and much of it was built when vehicles travelled at much lower speeds. Our geography is challenging, and our population base is small. This means it is difficult to spend the same amount per kilometre of road as the countries that perform better in road safety.

Waka Kotahi and local government work together to improve our roads and target improvements to where there is higher risk. While there have been some significant improvements in the road network in recent years, much remains to be achieved.

Engineering improvements such as median barriers are proven, effective and long-lasting, but they are not cheap. The new road safety strategy currently under development will seek a much greater level of ambition, including investment in roading improvements, but it is going to take time to make all our busiest, highest risk roads safer.

It will not be economic to invest in improvements to all our risky roads to make them safer at their current speed limit, so we need to consider other solutions too. This includes lowering speed limits where investment cannot be justified, increased enforcement and encouragement of safe road use.

“We are dealing with a system that involves human beings and we have a limited transport budget. There will always be some people who make a mistake or a bad judgment, and there will always be roads of less-than-desirable quality. Improving both of those areas will not happen overnight either. That's where lower speeds can improve crash outcomes now even when other parts of the system aren't perfect.” Glen Koorey, 2015

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Myth: Introducing a lower speed limit on its own won’t change traffic speeds

The evidence is very consistent that, for every 10km/h posted speed limit reduction, typically you observe a 2–3km/h reduction in mean or average speeds, all other things being equal. That might not seem much, but again research has found that every 1 percent reduction in speed generally results in a 4 percent reduction in fatalities (The World Health Organisation). So even a 2–3km/h drop in an urban area could mean 8–12 percent fewer fatalities.

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