Actually, it does. Speed can be 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 shows that reducing speeds has a direct impact on reducing deaths and injuries. The most recent study from the International Transport Forum (2018) [PDF, 7 MB] estimates that for every 5km/h reduction in average speeds, there is a 28% reduction in fatal crashes and a 26% reduction in serious injury crashes. The risk of an injury crash approximately doubles between 80km/h and 100km/h.
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:
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. 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.
Watch this Video: ‘What happens when you wipe off 5?'
This reconstructed crash advertisement by the Traffic Accident Compensation Victoria demonstrates what happens if you drop your speed from 65km/hr to 60km/hr in an accident.
See the ‘Road crash statistics’ (link is external) on the Ministry of Transport’s website.
Most crashes do happen at or below the speed limit, which supports the conclusion that the speed limits on some of our roads are too high, in fact we know that most of the speed limits on our higher risk roads are not safe and appropriate. For example, it’s relatively safe to travel at
100km/h on a 4-lane, median-divided road, but it’s not nearly as safe on narrow, windy roads with no median barriers or roadside protection.
Half of all injury crashes occurred on roads and streets where the speed limit was higher than the recommended safe and appropriate speed.
Speed affects the impact of every crash. The speed that people are travelling at the time of a crash contributes to the severity of the impact when a collision does occur.
As your speed increases, you travel further in the time it takes you to react and apply the brakes. You also travel further before you can bring the vehicle to a halt. We all make mistakes sometimes and speeding is one risk that drivers can minimise.
“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
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 the New Zealand 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 just 11 to 42 seconds.
Maximum speed (time before)
Maximum speed (time) after
Open road travel
80km/hr (06:30 - 06:48)
30-48 seconds difference
Local road trips
40km/hr (05:09 - 05:30)
11-42 seconds difference
A research project commissioned by NZTA [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% and reduced fuel use by about 15%.
The average social cost of a fatal crash in New Zealand is over $4.3 million. The total social cost of motor vehicle injury crashes to New Zealand in 2017 was calculated to be $4.8 billion. International studies estimates that for every 5km/h reduction in average speeds, there is a 28% reduction in fatal crashes and a 26% reduction in serious injury crashes.
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 NZTA 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)
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 still feel the force of a crash and even with modern safety features like airbags and crumple zones, many high-speed crashes are not survivable.
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.
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.
We know that the speed at the time of impact is a crucial factor in the severity and the survivability of a crash. It could be the difference between walking away from a crash or being carried away.
Many New Zealand roads are windy, hilly and often single lane, so they 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 default speed limits on the open road that are 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.
Improving everyone’s 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 behaviour results in crashes, many are the result of simple mistakes and even the most experienced and competent drivers make mistakes. Whether late for a meeting or work, or late dropping the kids off/picking up from school, everyday pressures can influence our behaviour and result in us making errors. These mistakes shouldn’t result in loss of life or a serious injury. The speed you are driving has by far has the greatest influence on the severity of any crash you are involved in, 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% and injuries by 30%, therefore around 50% of fatalities and 70% of injuries would remain (Elvik R, 1997.)
Many of New Zealand’s roads are not as safe as those in other countries. Our road network is comparatively long and remote, 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 we don’t have the same level or resources to invest as some countries that perform better in road safety.
The NZ Transport Agency 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 done.
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.
The current speed limits on many New Zealand roads are higher than what is safe and appropriate for how they are used. The cost of ‘engineering up’ all of these roads to make them safe at their current speed limit far exceeds the level of resource available. If we want to reduce the number of deaths and injuries on these roads we need to consider other solutions. This includes lowering speed limits, increased enforcement and encouraging safer 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
The evidence is very consistent that, for every 10km/h posted speed limit reduction, typically you observe a 2‐3 km/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% reduction in speed generally results in a 4% reduction in fatalities (The World Health Organisation). So even a 2-3 km/h drop in an urban area could mean 8-12% fewer fatalities.