There’s no doubtis a major factor in the number of deaths and injuries on New Zealand roads. It causes more injuries than, and it’s estimated that 87% of current speed limits are.
But there’s a counter argument that speed limits should only be reduced in “”, with school environs being the most common example. Widespread speed limit reduction, the argument goes, will waste drivers’ time and damage the economy.
But this assumes the only way speed limits affect society is through crash-related deaths and injuries, and through time lost travelling. So it’s important we recognise the other significant benefits that come from slowing traffic down.
Death and injury
The risk of injury or death if you are hit by a vehicle isat speeds below 50km/h. At 40km/h, for example, the risk of dying drops from around 90% to around 10%. For injuries, the greater reductions are seen at speeds of 20 or 30km/h.
found the introduction of 20 miles per hour (mp/h) zones resulted in a 42% reduction in road casualties, and the reduction was greatest in younger children. There was also no evidence of more people moving to drive on adjacent streets with higher speed limits.
Գ, a country with a population of 3.1 million that implemented a default urban speed limit of 20mp/h (30km/h), found the economic value of savings from lower accident rates to be in the region of NZ$180m in the first year alone. The total value is far greater if.
What statistics don’t show is the reality of the suffering road crash deaths and injuries cause. But survivors’ stories, such as thoseby transportation consultant Jeanette Ward, also powerfully demonstrate how lower speeds can save lives.
Economics and emissions
But what of the argument that slowing drivers down and prolonging trips mean the economy will suffer? There are two answers to this.
The first is thatlower speed limits in urban areas add virtually. You can see why in this simplethat compares traffic with different speed limits.
The second is that people don’t always productively use the time saved by faster travel. In fact,people often choose to travel further, especially for their daily commute. Making journeys faster can also encourage people to travel more often. This is calledand it adds to congestion.
Furthermore, there is a reasonably established relationship between the speed a vehicle travels and greenhouse gas emissions, with the lowest emissions being produced when a vehicle travels at around 55-80km/h.
However, this assumes a vehicle is moving smoothly, without stops and starts.are created when a vehicle has to repeatedly brake and accelerate. While individual driver behaviour can be a factor, the road environment and volume of traffic play a role too.
Research has actually found that in urban areas theto minimise emissions for small petrol cars is 28.2km/h. For larger vehicles, diesels and SUVs, CO2emissions are minimised with a maximum speed of 20km/h.
Pollution, noise and health
Nitrogen dioxide from traffic is estimated toeach year in New Zealand.with 20km/h speed limits.
The World Health Organization estimates traffic noise is theon public health after air pollution. Lower speeds significantly reduce noise, withthat “in urban areas with speeds of between 30 and 60kp/h, reducing speeds by 10kp/h would cut noise levels by up to 40%”.
Lower speed limits have also been shown to reduce health inequalities. One of the UK’s most eminent experts, Oxford University’s Professor Danny Dorling,was “the most effective thing a local authority can do to reduce health inequalities”.
This is particularly important, given rates of road injury and death in New ZealandMāori, younger people and low-income communities.
A range of other benefits from reducing speed limits are identified by Paul Tranter and Rod Tolley in their book. These include more physical activity from walking and cycling, time saved from not having to earn the money necessary to own and operate a car, and broader economic benefits for individuals and businesses.
Overall, reduced speed limits in urban areas would not only reduce injuries and deaths, they would also make our towns and cities better places to live.
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