Wellington Scoop

The $100m smart motorway – but it’ll all depend on the driving

The opening date of Wellington’s smart motorway is just around the corner, so we thought it would be worth taking a look at whether it’s really going to work as expected. Short story: the technology is impressive, but it’s a massive social experiment that may or may not work, given some of the less impressive driving habits of Wellingtonians.

The basic idea of the smart motorway is that it automatically smooths the flow of traffic to suit traffic densities, by dynamically altering the speed limit based on how much congestion there is. The intention is that travel times become more predictable, speeds are more consistent because there’s less stop/start queueing, and there are savings in time, stress, CO2, fuel, money … everything up to and including peace in Syria, if the pundits are to be believed.

The basis of the idea lies in the queueing theory – which in this case is the study of how to get all those vehicles to where they’re going as efficiently as possible. And that’s going to be quite important in the years ahead, given that the completion of Transmission Gully will see many more cars dumped at Wellington’s doorstep each morning as people trade the train for the car. So sorting out the backlog and funnelling the cars through the congestion point where SH1 and SH2 arrive in the city will be critical.

The NZ Transport Agency describes how the smart motorway works like this:

Smart motorways reduce congestion by carefully controlling the flow of vehicles. The most critical time when the system can influence the severity of congestion is as the traffic volume begins to build, ie before the road becomes congested. Detectors under the road and radars mounted on lighting poles and gantries count the number of vehicles in each lane, as well as the speed they’re travelling. The smart system calculates the rate at which the road is getting congested, factors in what’s likely to happen based on traffic records that are continually updated and monitored, and automatically adjusts the speed limit to pace the traffic and delay queues being formed.

And NZTA have certainly thrown the kitchen sink of technology at the project. There’s oodles of sensors, piles of computers, an entire stack of algorithms and even a flash new asphalt surface to reduce noise and spray. These guys look like they’re trying really hard to make this thing work – to the tune of chucking more than $100 million at the project.

Of course, it’s still just a road – so how well it works will depend on driver behaviour as much as bleeding-edge technology. And NZTA says that there two things that drivers need to do in order for the smart motorway to work as intended:

– Stick to the posted speed limit (the posted limit is the legal limit) – the smart system calculates the optimum speed to minimise congestion and to get the maximum number of vehicles through the area. As well as breaking the law, exceeding the speed limit will just get drivers to the back of the queue faster and just increase the size and duration of the queue.
– Minimise lane changes – changing lanes can have a shockwave effect on following vehicles. If everyone stays in the lane where possible, traffic moves smoothly and everyone gets where they’re going sooner.

And there’s the two problems right there. For starters, NZTA is asking people to actually stick to the speed limit, which will vary based on the time of the day, the amount of traffic, the phase of the moon and a whole bunch of other factors that may be totally invisible to the person behind the wheel. To put it mildly, Wellingtonians aren’t very good at sticking to the speed limit even when it doesn’t change.

Here’s an experiment you can try in order to prove the point. There are roadworks through a big part of the smart motorway section on SH1/2, they’ve been there for ages, and there are 70km/hr signs all up and down the stretch of road. So try setting cruise control to 70km/hr or thereabouts in the middle lane … and watch the traffic zoom past you on both sides, as the bloke behind relentlessly tailgates to try and get you to speed up.

I tried it a few days ago and was passed by practically everything on the road – including a brace of taxis, more courier vans than I could count, a handful of trucks and a bus. All these people are supposed to be professional drivers, yet they looked more like professional scoff-laws. And that’s when the speed limit is fixed, and is in place for the safety of the people in the fluoro vests on the side of the road.

Of course, when you actually stick to the speed limit, NZTA’s other smart motorway rule – don’t randomly change lanes – flies out the window as well. The most entertaining was the courier van who was executing a huge multi-lane weave through traffic like a latter-day Ayrton Senna, before finally dashing across the separator between SH2 and SH1 as he responded to the magnetic pull of the Ngauranga Gorge. I won’t say who the courier company was, but will note that the van was yellow – presumably so the rest of the world could see him coming and prepare themselves for the impact.

The fact is that Kiwis are rubbish drivers. We’re routinely in the lower ranks of the developed nations when it comes to road fatalities, the crash reports are filled with examples of the most appalling judgement, and the road toll is on the rise. So expecting Wellingtonians to drop their normal driving habits – I’ll drive at the speed that suits me because the road ahead doesn’t have much traffic on it – seems like a big ask.

The smart motorway is like NZTA asking drivers to stop texting, cease applying their lippy, look up from the end of their bonnet and start driving with their brains rather than their egos, so everyone gets to work a bit faster. It will be fascinating to see if Wellington responds.


  1. Patrick Morgan, 16. June 2016, 17:19

    $100 million? Your source please. [The figure is provided by the NZTA.]

  2. Ian Apperley, 16. June 2016, 18:21

    Not sure I agree. Bottom line is that we won’t know until it actually gets switched on. The UK has had reasonable success with similar deployments.

  3. PCGM, 16. June 2016, 20:58

    And apparently smart motorways work like a dream in Germany. But to state the obvious, this isn’t Germany – and NZ has nearly three times the road toll per capita than they do.

  4. JC, 17. June 2016, 12:35

    No, NZ isn’t Germany. We have many dangerous country roads. But the motorway isn’t one of them – it’s almost the closest thing we have to a German road. So a comparison to UK/Germany in this instance is fair.

  5. Richard Keller, 17. June 2016, 14:07

    I think we should see some sort of relationship between the bad driving habits of Wellingtonians (New Zealanders) and the uproar in Island Bay. In Island Bay what we see is a response to the fact that the cycleway challenges, or appears to challenge, the total dominance of the motor car in transport planning; finally something has actually been built, rather than just talk. In terms of current, local politics, the motor car can be seen as a fundamental ingredient in the psyche of the country. No future in that, so the future is viewed with suspicion.

  6. Curtis Nixon, 17. June 2016, 17:19

    $100 million plus – (I love how NZTA lists an open-ended amount) – seems like an incredible amount for what are improvements to an existing road. We could have built a light rail system from Wellington Railway station to the airport for that amount. Being a new piece of much needed infrastructure as opposed to tarting up something we already have.

  7. David, 17. June 2016, 18:06

    To the best of my knowledge, the $100million plus figure includes the yet to be built 4th southbound lane. The Dompost article says the smart motorway costs $55million.

    Curtis, the 2013 Public Transport Spine Study said that one light rail line to the airport would cost around $900million! I am yet to be convinced of the benefits of light rail especially when 90% of public transport trips from some major suburbs would be forced to make transfers (and wait) at hub stops.

    Richard, I don’t think cycleway opposition is because “people hate anything other than the car.” Not even close. If you have followed Ian Apperley’s former blog Strathmore Park, you will see exactly why people opposed the IBCW. Some of those who oppose IBCW are bicycle riders too.

  8. JC, 17. June 2016, 18:20

    Curtis Nixon – seriously??? It’ll cost a truckload more than $100m to build a light rail system. If it was only $100m it would have been done years ago.

  9. Richard Keller, 18. June 2016, 11:38

    I expect the Wellington ‘Smart Motorway’ will not include ‘smart billboards’ which I recently read are operating in Boston (others?) along motorways. These so-called smart billboards read the cellphones in the traffic whizzing (or not) by, create some kind of profile from the available databases of those cellphone owners, then adjust the item advertised on the billboard. I’m sceptical of the efficacy this operation, but perhaps I’m wrong. Analysing the information gleaned from so many cars could only reveal minor differences through time I would have thought; it sounds like a toy.

  10. Troy K, 18. June 2016, 16:04

    It’s not smart, it’s unnecessary and costly.

  11. Alexandra, 19. June 2016, 7:17

    How is more pointed advertising for products and the distraction from reading billboards on the motorway “smart”? … and the collection of private data is very 1984.

  12. Curtis Antony Nixon, 19. June 2016, 10:40

    David and JS. I cleverly used the $100million PLUS that NZTA lists on its website, to cover my loose statement that it would be enough to build a light rail system. If it’s good enough for NZTA to use open-ended figures . . .

    And David, the 2013 Public Transport Spine Study stupidly included in the cost of the light rail a very expensive tunnel next to the existing Mt Vic car tunnel because bizarrely they chose for their preferred route a track around the Basin, Mt Vic and Hataitai (Highway 1): whereas going up Taranaki, John and Riddiford Sts is best to eliminate congestion at the Basin, plus it gets you to the hospital and Newtown, thence through Kilbirnie to the airport.

    And yes, please transport gods, get transfers sorted out on Wellington public transport so people can move across modes and services like in the rest of the world. The only reason we don’t have it here is that it is another way Infratil can impose its scarcity pricing model, thus charging people all over again and making as much profit as possible.

  13. PCGM, 19. June 2016, 20:46

    Curtis – The difference between your fudging of the numbers and NZTA’s fudging of the numbers is that they used the plus sign, while you used the multiply sign. According to my back-of-the-envelope calculations, the $100 million that the Transport Agency are spending on the smart motorway would have built a light rail system from the railway station to about halfway down Courtenay Place. How would that have eased congestion, exactly?

  14. Helen S, 20. June 2016, 8:15

    Both NZTA and the WCC fudge data. Like the silly motorway, fudging facts to waste money and get us more in debt is not ‘smart’.

  15. Curtis Antony Nixon, 20. June 2016, 8:34

    Sorry PCGM, I think you need new glasses. I wrote the word PLUS, not a multiply sign. A light rail line from the railway station to the end of Courtenay Place would be a good start.

  16. Ross Clark, 21. June 2016, 21:28

    If we really want to control Wellington traffic, we need to control commuter parking, but I do not think that anyone has the bottle to do this.