There鈥檚 no doubt听听is a major factor in the number of deaths and injuries on New Zealand roads. It causes more injuries than听, and it鈥檚 estimated that 87% of current speed limits are听.
But there鈥檚 a counter argument that speed limits should only be reduced in 鈥溾, with school environs being the most common example. Widespread speed limit reduction, the argument goes, will waste drivers鈥 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鈥檚 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 is听听at 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.
听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.
搁别肠别苍迟听, 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听.
What statistics don鈥檛 show is the reality of the suffering road crash deaths and injuries cause. But survivors鈥 stories, such as those听听by 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 that听听lower speed limits in urban areas add virtually听. You can see why in this simple听听that compares traffic with different speed limits.
The second is that people don鈥檛 always productively use the time saved by faster travel. In fact,听听people often choose to travel further, especially for their daily commute. Making journeys faster can also encourage people to travel more often. This is called听听and 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.听听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 the听听to minimise emissions for small petrol cars is 28.2km/h. For larger vehicles, diesels and SUVs, CO2听emissions are minimised with a maximum speed of 20km/h.
Pollution, noise and health
Nitrogen dioxide from traffic is estimated to听听each year in New Zealand.听听with 20km/h speed limits.
The World Health Organization estimates traffic noise is the听听on public health after air pollution. Lower speeds significantly reduce noise, with听听that 鈥渋n urban areas with speeds of between 30 and 60kp/h, reducing speeds by 10kp/h would cut noise levels by up to 40%鈥.
Lower speed limits have also been shown to reduce health inequalities. One of the UK鈥檚 most eminent experts, Oxford University鈥檚 Professor Danny Dorling,听听was 鈥渢he most effective thing a local authority can do to reduce health inequalities鈥.
This is particularly important, given rates of road injury and death in New Zealand听听M膩ori, 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听. 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.
This article orginigally published on听.
