In brief

• New revelations challenge the long-standing ‘speed kills’ narrative.

• Police admit they lack evidence that speed is the main cause of fatal crashes.

• Crash investigations don’t focus on identifying root causes.

• Reckless decisions, fatigue, and other factors may be more critical than speed.

• Public messaging campaigns often restate clichés rather than addressing true crash causes.

Challenging the ‘speed kills’ narrative 

For decades, New Zealand Police and road safety campaigners have bombarded the public with messaging that “speed kills” or “speed was a factor in 34 percent of fatal crashes”, but Police have now just admitted they don’t actually know.

Police admit no evidence speed is primary cause of fatal crashes

The stunning admission comes in a series of documents released to Centrist by Police and NZTA Waka Kotahi under the Official Information Act.

Centrist decided to probe deeper than the official soundbites that are often run, and asked Police a series of questions:

1. Copies of any studies on fatal road crashes in NZ that detail to what extent speeding was the primary cause of the crash (ie, but for excessive speed the crash would not have happened)

The Police response?

“Police has not conducted any such studies. This part of your request is therefore refused pursuant to section 18E of the OIA as the document alleged to contain the information as requested does not exist,” replied Superintendent Steve Greally, Director of Road Policing.

2. The studies I have repeatedly seen quoted in NZ road safety literature are merely observational studies noting a general association between speed limits and fatalities. Observational studies, particularly on low frequency events, are regarded as low quality in the sciences. Do you have copies of ANY studies in NZ or globally that have taken a randomised sample of detailed crash reports and actually worked out what the top five real primary causes (the ‘but for’ test) of fatal road crashes are?

“Police has not conducted any such studies. This part of your request is therefore refused pursuant to section 18E of the OIA as the document alleged to contain the information as requested does not exist.”

Centrist also asked whether traffic crash analysis reports – the investigations police do when they close the road for hours to comb the crash scene – are “designed to deliver a primary cause of each individual incident? If not, why not?”

What police crash investigations really reveal

The Police admitted they don’t investigate to find the root cause of a fatal crash:

“Crash analysis by Police does not report on ‘primary causes’ as such. The identification or otherwise of ‘primary crash causes’ and the interaction of various risk factors in the incidence of traffic crashes is complex and the identification of ‘primary causes’ is not necessarily helpful in determining the cause of a crash when multiple factors might be at play.”

All of which casts the incessant messaging about the significance of speed, used to justify lower speed limits and “traffic-calming” measure like speed bumps, in doubt.

Addressing the real cause of road fatalities

No sensible observer questions the laws of physics involved. A 2.2 tonne EV hitting a 1.6 tonne ICE vehicle head on with both cars travelling at the legal open road limit results in an impact speed of 200 km/h. So to that extent, speed and mass are both “factors”. Yet the speeds were legal, not excessive, and the real primary cause of a head-on is actually that someone is in the wrong lane – either recklessly, or through inattention, or fatigue, a medical event or they were drunk. Trumpeting “speed was a factor” is as meaningless in that particular example as remarking that the sky was blue.

Given that NZTA, Auckland Transport and others have noted that a car crash at 50 km/h can be fatal, two cars colliding head on in a suburban 30 km/h zone can still have an impact speed of 60 km/h, so the Road to Zero vision of the last government would need ridiculously low speed limits(with drivers actually following them) to actually achieve zero.

So, Police do catch-all crash investigations that appear to box-tick the obvious potential factors, and this in turn allows for expensive public messaging campaigns re-stating cliches. Yes, it is technically true that the faster you go the bigger the mess, but how much slower would you have to be moving to avoid any risk of fatality? An open road head-on at 50 km/h each way is still the same as hitting a parked car at 100 km/h.

Meanwhile, the real causes of road fatalities like reckless decisions or fatigue go largely unaddressed because Police have not  found out why crashes really happen.

COMING UP IN Part Two: what NZ’s official crash data really reveals about crash causes

COMING UP IN Part Three: why NZTA is changing its flawed approach to crash investigations