John Williamson: Don't underestimate risk on the road

Research shows we under-estimate some risks and over-estimate others.

It started as an email conversation.

"There is a growing concern on the coast about the incredibly high number of crashes at Murphy's Hill (just past Ngunguru Ford Road heading towards the coast). I receive community alerts on the Tutukaka Coast Facebook page and there have been at least six over the past three months, highlighting run off road and advising others about slippery roads."

Here we have a great local network wanting to warn others about the current dangers but is this a problem road and if so what is being done about it?

An email message to Jeff Devine — WDC's Roading Manager — got the following response: "There have been six recorded accidents on the stretch of Ngunguru Road between Ngunguru Ford Road at the top of the S Bends and Coalhill Lane at the bottom of the hill, between 2006 and 2015 (that's 10 years!). They were all loss of control.

There is however, only so much that roading engineers can do. The road rules require us to adjust speed according to the road conditions.

One was alcohol-related, one fell asleep and four occurred during heavy rain. Two of these were serious head-ons and there were no fatalities. There are speed advisory signs and chevrons on all corners.

This stretch of Ngunguru Road has a medium personal and collective risk and will be looked at as part of the Speed Management Guide review."

What this means is that local people observe a lot more crashes than are being reported as serious and if you want to know where a problem spot is then you ask tow truck drivers and insurance companies rather than rely solely on official crash analysis data.

This raises the question about what actually is the problem with Ngunguru Road and how do drivers perceive any risk there might be on this particular stretch?

The issue of how well drivers perceive the risks of the road has been the subject of an NZAA Research Foundation study published recently. The Foundation commissioned two research projects by Sam Charlton's team at Waikato University.

One of these compared actual and perceived risk and that was followed by a study that examined how safety "treatments" such as road markings, affect drivers perception of risk and influence the speeds that drivers choose to travel.

A key finding from the project was that Kiwi drivers generally perceive risk well but that we do under-estimate some risks and over-estimate others.

We over-estimate the risk from bends and narrow lanes but we under-estimate the risk from intersections and roadside hazards such as narrow shoulders, ditches, trees and power poles. As a result of these latter road features they are less likely to receive due care and attention.

The study suggested that double yellow lines and wide centre lines were more effective at communicating risk rather than dashed white centre lines, but that nothing quite beats the presence of a police car at communicating risk and slowing drivers down.

Now, how might this study relate to the high non-serious crash rate that local people talk about on Murphy's Hill?

My ordinary driver analysis of this road is that this particular stretch needs some different messages on and about it.

You drive from Whangarei through native bush and past stone walls which tend to create a perception of a narrower road which naturally slows you down. You exit the bush at Ngunguru Ford Road and before you is a long sweeping road with open distant views and you might see the chance to plant boot.

The road has sweeping S Bends and is relatively narrow but seems wider. The curves themselves may well be slightly out of context and the road is overall, unforgiving. If you lose control you will end up in the paddock, but the road itself does not communicate much risk.

To me, this is a classic stretch where you might under-estimate the risk. While there are curve advisory signs of 45km/h and chevrons, this particular stretch could benefit from a different "treatment".

Perhaps a wider centre line which tends to perceptually narrow the road to communicate the risk of losing control and slow drivers down. A lower speed limit over the whole road should also be publicly consulted.

There is however, only so much that roading engineers can do. The road rules require us to adjust speed according to the road conditions.

It seems to me that what Tutukaka Coast residents are saying, is that this particular stretch is dangerous, particularly in heavy rain conditions and adjusting for that risk is part of safe driving behaviour.

Drive safely, enjoy your driving and share the road

* John Williamson is chairman of Roadsafe Northland and Northland Road Safety Trust, a former national councillor for NZ Automobile Association and former Whangarei District Council member.