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Are lower speed limits really safer?

In Australia, especially in cities and busy suburbs, speed limits are on the way down. The message is clear: speed kills. It makes sense that moving more slowly creates less impact if you are forced to stop. But what if moving too slowly changes the way you drive?

Danish experiments

In 2005, the Danish government increased limits from 110 kmh to 130 kmh on motorways and the death rate on those roads fell.

A further experiment in Denmark, beginning in 2011, found accidents decreased on country roads after raising speed limits from 80 to 90 kmh. While the slowest drivers drove faster, the fastest 15% drove 1kmh slower so the average speed was similar to before. There was also less overtaking, a potentially hazardous manoeuvre.

Open limits

The Northern Territory Government trialled open speed limits up to 300 kmh on stretches of the Stuart Highway in 2014. During this trial, 85% of drivers travelled at 133-139 kmh and mostly to the conditions. There were 11 crashes, no deaths and one serious injury was the result of alcohol and no seat belts.

In the year to October 2016, fatalities on NT roads were down 12.2% compared to an increase of 14.5% in NSW. Even so, the new NT government says voters want the 130 kmh limit reinstated for safety reasons.

Attention deficit

A recent study by University of Western Australia found strict enforcement of speed may cause drivers to direct more attention to watching their speed than detecting hazards around them. Participants who were given a stricter speed limit threshold also rated the experience of driving as more demanding.

The study did not suggest this, but could drivers be more easily distracted by mobile phones because driving slowly does not take their full attention?

World road toll

The road toll has fallen in most western countries, including Australia, because:

  • Modern cars are becoming safer
  • Roads are becoming safer
  • Better medical attention means people seriously injured are less likely to die
  • Speed cameras help deter drivers.

In spite of these positive factors, the road toll in NSW was worryingly up in 2016.

Figures from International Transport Forum OECD, 2014-5, show Australia is still a relatively safe place to drive - but not as safe as Germany, UK or Norway, for example. This is surprising, given that Germans drive at very high speeds on the Autobahns and UK roads are fast moving and highly congested.

Deaths per Deaths per
100,000 10,000
population vehicles
Norway 2.3 0.37
UK 2.9 0.51
Germany 4.3 0.61
Australia
5.3 0.66
NZ 7.0 0.87
USA 10.2 1.19


What to do about speed limits?

One view is to apply the 85th percentile principle to setting limits – limits that 85% of drivers would not wish to exceed. However, speed limits in Australia already seem much lower than this.

Road safety authority, Robert Solomon, has studied international approaches to road safety and claims: “a competent driver at 120 kmh is far less dangerous than an incompetent one at 80 kmh”. Perhaps it is time to pay attention to improving driving skills and create a more demanding test for a driving licence.

CTP insurers may reward safer drivers with cheaper green slips.