It's hard to have a rational discussion about speed. Some people are in your face about the hoons who just roared past them and narrowly missed a crash. Pedestrians describe their near-miss as red-light runners sped through the intersection.
Most of us see ourselves as above-average drivers who stick to the speed limit, and we yearn to see a speed camera around the corner as idiot drivers speed past.
It's curious when, as Northland AA has raised the level of conversation about the parlous state of our state highways, that NZTA's response is a review of speed limits across the Northland state highway network.
Over the past five years, road-controlling authorities have been implementing speed limit reviews over the top 10 per cent of our roading hotspots using new speed management guide principles.
This involves a discussion with the community around targeted roads with three options. These are:
Self Explaining, where the speed limit is set to the feel and operating speed of the road;
Engineer Up, where a strong case is made to bring the road up to the required standard to support higher economic needs;
and Challenging Conversations, where it is likely that a speed limit reduction is an unpopular likely outcome.
Now, though, we have a review of the whole Northland network as a test case with a possible outcome being a speed limit reduction across all our state highways, and that will generate some emotional reactions.
Before we even consider that possibility we need to adopt some non-negotiable principles, namely:
• That any new speed limits should closely match the operating speed of the road and they make sense;
• that our roads will have a continuous programme of capital improvements;
• that there is no trade-off between reduced speed limits and enhanced road maintenance, and that any new speed limits are well communicated with adequate enforcement and reasonable tolerance.
In laying down some principles we also need to examine the facts about Northland roads and establish some hard evidence of the need for change.
Our road crash statistics are the worst in the country. We have 14.4 deaths per 100,000 people compared to the New Zealand average of 6.3. Our hospitalisations from road crashes are 108 per 100,000 people as against the national average of 69.
Most of our fatal and serious injuries are from head-on or run-off-road single-vehicle crashes. Around 20 per cent of our fatal and serious crashes are identified as inappropriate speed, although multiple factors are often involved.
The average speed on Northland highways is 85-95km/h. Generally we drive at below the posted speed limit. Multiple research evidence identifies that dropping the speed limit by 10km/h creates an observed reduction of 2.5km/h and we generally use our instincts about the speed we should be driving.
What is lacking in most speed reviews is the case for and against any speed limit reduction. The case for is about having more time to react and a less severe impact of a crash as well as a more acceptable environment for walking and cycling.
The case against identifies longer travelling time, higher fatigue, reducing traffic efficiency, more congestion, having to watch the speedo, frustration with slower drivers, revenue-gathering and the potential to reduce road maintenance because of lower traffic impacts.
There is reasonable international evidence that reducing speed limits reduces the incidence of serious and fatal crashes but is there an acceptable level of road trauma against the economic costs?
It's the potential to reduce road maintenance which is of most concern, and this cannot be a trade-off for a reduced speed limit.
Skid resistance and roughness are the road quality measures that have the biggest influence on road safety and Northland state highways remain significantly lower than most other regions by this measure.
A trial by NZTA four years ago indicated that a 10km/h speed limit reduction brought the skid resistance of previously high-risk curves to within acceptable limits. It's a potentially cynical way of sweating your roading assets.
Reasonable people will agree to reasonable speed limits that do not include a maintenance trade-off.
One size does not fit all and you can't make people do something just by putting up a sign.
• John Williamson is chairman of Roadsafe Northland and Northland Road Safety Trust, a former national councillor for NZ Automobile Association and former Whangārei District Council member.