New speed policy leaves evidence in rear view mirror

Wednesday, 26 June 2024

“The evidence shows clearly that higher speeds result in higher crash rates, more severe injuries and more deaths,” writes Lin Roberts.

Dr Lin Roberts is a biological and social scientist with decades of experience in a range of areas including public policy, management and governance. Her most recent role was as a senior lecturer in sustainability and environmental management at Lincoln University.

OPINION: Faster is better, right? This seems to be the main assumption underlying the coalition Government’s plan to raise speed limits.

The proposal is to increase speed limits on ‘Roads of National Significance’ to 110kph or even 120kph, require councils to reverse local speed reductions put in place since 2020, and limit the hours during which speed reductions around schools apply.

Regulation Minister David Seymour is fond of saying he likes evidence-based policies, but the inconvenient truth is that the evidence all indicates these are silly ideas.

A sensible approach would be to examine the evidence about the impact of speed changes where it has been tried. Yet despite saying all speed rule changes should involve a cost-benefit analysis, the proposal document - it’s out for consultation until July 31- includes none of this information.

Fatalities and injuries

The evidence shows clearly that higher speeds result in higher crash rates, more severe injuries and more deaths. Auckland Transport found roads where speed limits were lowered on June 30, 2020 experienced a 47% reduction in deaths in the next 18 months, a reduction in all injury crashes of more than 25%, and a greater than 15% reduction in serious injuries. Rural roads have seen a 71% reduction in deaths and a drop of more than 25% in serious injuries. And all during a time when deaths and injuries on other roads increased.

In Christchurch, a comparison of reduced speed areas in Addington, Sumner and Papanui with adjacent areas with no speed reductions found a 59% reduction in injuries from less severe crashes.

These are not just statistics. These are our family members, friends and colleagues.

In Wales, one leading car insurer has reported a 20% drop in vehicle damage claims since the introduction of a nationwide 20mph (32kph) speed limit in built-up areas last September.

Consumption, emissions

Higher speeds also increase fuel consumption. Auckland Transport found average fuel consumption dropped 14-15% when the speed limit was reduced from 100kph to 80kph on the open road. Conversely, driving at 110kph instead of 100kph uses about 15% more fuel. Fuel is not only a personal cost; given we import all vehicle fuel, it also impacts our balance of payments.

Traffic flow on Christchurch’s 30kph one-way streets is “smooth and efficient, with green lights most of the way”, writes Lin Roberts.

Increased fuel consumption means increased greenhouse gas emissions. In 1997, New Zealand made a commitment in Kyoto to get our emissions down to 1990 levels, but they have steadily risen since, with transport the biggest culprit. In 2022, GHG emissions from transport were up 62.1% from 1990, mainly made up of road vehicle emissions (91.2%). Under the previous government, progress was at last being made to stabilise and reduce these.

However, the current Government is determined to reverse that. The Clean Car discount has been scrapped. So too have bus discounts and cycleway funding that make alternatives to car use much more attractive. Now Transport Minister Simeon Brown plans to increase speed limits and weaken the Clean Vehicle Standard, so fuel use and emissions will rise again.

Particulates and nitrogen dioxide emissions increase with more, faster vehicles. The 2022 Health and Air Pollution in New Zealand study estimated the social costs of the health impacts of nitrogen oxides alone as $15.6 billion.

Time saving and productivity

If I can drive faster, I’ll get there sooner, right? And (maybe) I will then be more productive. It turns out that people consistently overestimate how much time they will save by increasing their speed.

Are We There Yet? is a new series from The Press examining the transport challenges facing Christchurch - New Zealand’s second-largest city.

Increasing average speed from 80kph to 100kph on a 10km trip saves only 90 seconds, assuming you maintain the 100kph average all the way. In Sweden it was found a 10kph increase in the speed limit resulted in a mean speed increase of only 3kph, while in Madrid a 20kph speed reduction on their ring road left average travel times virtually unchanged, but reduced CO2 and NOx emissions by 14.4% and 16.4% respectively.

As a 2017 “real world” New Zealand study found, traffic, road conditions and intersections have as much or more influence on drivers’ speed as the maximum limit.

Mike Yardley (Change in direction on Christchurch transport, June 18) clearly rates the illusion of speed above the evidence. He argues that speed reductions “knee-cap the efficient flow of cross-city traffic”, yet the traffic flow on the 30kph one-way streets is smooth and efficient, with green lights most of the way. The roads mainly used by trucks and freight vehicles, such as Moorhouse and Brougham, do not have reduced speeds. It is clear here congestion and intersections have most impact on the average speed of travel.

Liveability

The good news is that while higher speeds make streets noisier and decrease the willingness of citizens – from school children to the elderly – to walk and cycle in their city, the converse also applies. Lower speed limits make streets safer for playing, walking and cycling, encourage more people to walk, wheel or cycle, thus making our communities safer and improving health and wellbeing.

This is why in Christchurch, as in other New Zealand cities, neighbourhood after neighbourhood has lobbied the council to reduce the speeds in their areas.

It would presumably enhance productivity to have people spending less time sitting in cars and trucks. But the main problem here is the number of vehicles on the road. Better travel times (and more liveable cities) can be achieved more effectively, and at much lower public and private cost, by shifting more freight to rail and coastal shipping, significantly improving public transport options, and making cycling and walking more attractive.

(CORRECTION: Updated 26/06/2024 10:29am The 14th paragraph has been updated to make clear that a 10km journey takes 90 seconds less at 100kph than 80kph)

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