Changes to the lane layout of the Victoria Park viaduct will be happening on Monday – finally enabling the use of the entire viaduct for southbound traffic. This has the potential to provide the biggest increase in capacity from the whole project, adding two southbound lanes and (hopefully) putting an end to the significant delays experienced by southbound traffic in the morning peak most particularly.
As the NZ Herald reports, the new layout has been partially operational for the past week or so, with one southbound lane being shifted onto a part of the viaduct previously used by northbound traffic. This led to quite a bit of confusion among drivers:
The change doubles the capacity for southbound traffic, but the Transport Agency acknowledges it could cause considerable confusion, because it has been unable to remove a barrier between the flyover’s two sets of lanes.
That is because the barrier separates what are effectively two viaducts, at different heights from one another.
Drivers going to Cook St or the links to the port and to the Northwestern Motorway must use the two lanes on the left of the viaduct.
Those wanting to continue south can do so only from the two lanes on the right.
A limited version of the split has been operating since early last week, when the agency made one of the lanes on the right available to southbound traffic for the first time.
That caused queues back to Esmonde Rd in Takapuna on the first day.
Traffic came to a halt as drivers dithered over which flyover lane to choose, even though southbound vehicles have still been able to use either lane.
By coincidence, I found myself having to negotiate this new arrangement, heading back towards SH16 from the Harbour Bridge this evening. And it certainly was confusing as at one stage I was pretty certain that I’d picked the wrong lane and was going to be forced off at Fanshawe Street. I’m guessing from the layout that everyone heading further south than SH16/Port thought they needed to use one lane (whereas actually they had a choice of two), causing the big traffic jams the article talks about.
Here’s a useful video from NZTA explaining the new lane layout that will be in operation from Monday:
It will be interesting to watch traffic flows on Monday, which still should be down on normal a bit (for example, I don’t return to work until the 16th). Implementing motorway changes resulting from constructing the Victoria Park Tunnel has been a bit of a disaster so far – so I’m sure NZTA will be hoping things go smoothly.
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Intuitively you would expect that two lanes split across two traffic streams adds up to much less than the four that are available, because of the “wasted” capacity that is created from not being able to balance flows across all lanes at once. So while we’ve added two lanes (by way of the tunnel) we get much less than two lanes of additional capacity. I’m very interested to know how this was modelled …
Whoops, meant to say “four lanes split across two traffic streams adds up to much less than four”
On the flip side Stu you get the traffic flows sectorised with far less need or opportunity to change lanes once you are in your sector. The days of inconsiderate drivers flying down the Fanshawe bound lanes then forcing their way on to the southbound lanes are long gone.
It also means that a tailback on the southern won’t affect the SH16 links as much, and vice versa to some extent.
Good point – so there’s a downside (in terms of vehicle throughout) from less effective use of capacity (because the flows in the two streams are likely to be unbalanced), but an upside from more “laminar” flow in the two streams. Be interesting to know whether the net effect is more/less capacity …
2010 traffic data tells us the following splits (although likely to change as a result of the project):
SH16/Port southbound offramp: 14,180 vehicles a day
SH1 southbound: 29,954 vehicles a day
So quite unbalanced, but I would expect when Waterview opens there will be much more traffic from the Shore heading west, and I think more traffic will use the Port exit to access the city centre rather than Fanshawe/Cook Street.
http://nzta.govt.nz/resources/state-highway-traffic-volumes/docs/SHTV-2006-2010.pdf
As an aside to your point about Waterview, if this is the case isn’t it mad to direct traffic into town to get to the shore…? CBD as traffic sewer: the role that the likes of Phil ‘Cities Matter’ McWhatsit see for the city, a conduit for inter suburban traffic but of no particular value in itself.
I do hope that the billions spent on SH20/16 and the upper harbour, do mean that Ak finally gets a functioning ring road. I heard of a plan to change the designation of 20 to 1 post Waterview, thereby encouraging regional traffic that way. Anyone know about this?
I also suspect more people may start using the Port exit instead of Fanshawe St as a result of the Vic Park project. At the moment It can often be quicker to use Fanshawe St going to/from an eastern CBD/ Parnell location
Swan, well that’s all good, rather than than have people drive through town to get to Parnell or the east side of the city…. especially as it looks like there may well be even less port raffic…
Yes, exactly. So an opportune time to do things like reduce capacity on Quay St through town, get rid of the lower Hobson St Viaduct etc…
With regard to the Fanshawe St lanes being used to queue jump onto the viaduct. I’m not sure that particular maneuver will be entirely eliminated.
I’ve had to drive through this section for several years in the mornings and I’ve noticed that cars which have slowed everyone down by forcing their way into the southbound lanes will often then exit at Cook St. This is a pathway from one point to another that could just as well be accomplished by going off at Fanshawe St. and up past Victoria Park market.
The savings in time and distance would appear to be trivial compared to backing up two lanes of a major highway. This short run along and then off the viaduct will still be possible under the new layout though it will now only affect through traffic for the Port and SH16.
Answer; ditch the cook St off ramp. see below…
My feeling is that this will work better than having four lanes with no separation. However, it will take much more getting used to.
As an aside, I’d intuitively think that the benefits of reduced vehicle weaving (e.g. changing lanes) would be unlikely to be picked up by a strategic transport model (such as SATURN, EMME) because they model vehicle demands as a continuous flow. Maybe they applied differential speed-capacity curve to the highway sections after the two vehicle streams split?
Alternatively, maybe they used a micro-simulation model (e.g. Paramics, AIMSUN, VISSIM) to capture the impacts of less weaving on the flow of individual vehicles. Interesting stuff anyway, and possibly a good opportunity to investigate the relative strengths/weaknesses of strategic versus micro-sim models.
I wonder if there would be a benefit in extending the separation right through St. Mary’s Bay from the moveable barrier up to the start of the viaduct?
That way the weaving and indecision would be removed entirely from that section and drivers would have to choose their respective lanes before reaching the Bridge. This choice has to take place in any case since the southbound Bridge in the morning is already separated into two clippon lanes on the left and three lanes of the old bridge on the right.
Good thinking Gary, could work.
Admin do you know the Cook St/Fanshawe spilt? I would love to see the end of the Cook St off ramp for the enormous benefit that would give to whole of the Freemans Bay slope up to Nelson St. The old street pattern could be restored and an area with enormous value and potential developed. For the city to realise this value the construction of thousands of new carparks must be prevented on the old City Council site and the new Sky City monstrosity, with their huge additional circulation take-over of the entire street network.
If you were to extend the physical barrier between Fanshawe/Cook/SH16 and SH1 it would be a little like one of the goals of the proposed harbour crossing, to separate the SH1 through traffic from the commuter traffic headed to the city (I realise SH16 is still in with the commuters).
One way to overcome the issue of Onewa interchange access to the central SH1 lanes would be the same solution I have proposed for the harbour crossing, that is to construct a second set of ramps from Onewa interchange to the SH1 lanes (leaving the existing ramps to access the City/SH16 lanes). You’d effectively have two separate motorways, just with one physically located in the median of the other.
Yes and therefore no need for any additional vehicle crossing… just the missing mass transit one.
I think a problem with that proposal is for vehicles getting on at Onewa Rd and heading south past all the city exits. You would be forcing a really extreme lane change for them to get across in time.
Patrick the link I posted in the comment above with the volumes should answer your question.
Hey that’s fascinating! Cook St off ramp has been declining crazily: 2006: 16 666 -> 2010: 7687. That’s a plunge of over 50%. …. And look Fanshawe has declined too, less dramatically: 2006: 20 286 -> 2010: 16 576. Got to be the Northern Busway.
So there is absolutely no need for any extra harbour car crossing, at least with city off ramps. And with the western ring road and improvements to Bus privilege and integrated ticketing and bus coordination on the Shore this trend could continue.
Also the Fanshawe St intersection has five lanes [+one buslane], the new St Mary’s configuration have these five lanes fed from one traffic lane and one bus lane [that looks intermittent] as far as I can tell from the video above. So how unworkable would it be to close Cook St off ramp and send two full lanes plus buslane to Fanshawe? in 2010 the combined vehicles for the two off ramps was 24K, in 2006 the old Fanshawe off ramp handled just over 20K alone, still plus 25% but there is a whole lot of new road to go into now. I guess it depends on what the intersection can process…?.
That would also fully sort the lane confusion; all city traffic left lanes, all SH1, SH16, and port traffic the intuitive right hand lanes.
PS I think it’s counterintuitive to not have the SH16 lanes to the right as mentally that’s where you’re are heading….
Patrick, you seem to be forgetting every road builder’s favourite: induced demand. If doubling the number of car lanes while only half building a bus lane doesn’t rekindle traffic growth over the bridge (and Cook St off-ramp) nothing will…
The reason for Cook Street’s decline in volumes (you can see the same for Wellington St) is that once the SH16/SH1 ramps were hooked up (late 2006 from memory) traffic heading between the northern motorway and the northwest motorway didn’t need to exit anymore.
Yes the big drop is between 2006 to 2007, but it has kept declining steadily each year since, but anyway Cook St then was principally a temporary route for connecting the two motorways…. all the more reason to close it now and get this part of the city back.
Yeah most of the motorway network, like the entire state highway network around the country, has seen negligible traffic growth for the past few years. Here’s data from the southern motorway: