It’s generally accepted that the Victoria Park Tunnel represents probably the most cost-effective project out of the entire Roads of National Significance package. This was confirmed by the SAHA report, which puts the VPT miles ahead of any other project in terms of its cost-benefit ratio:
For southbound traffic, the project has worked wonders – at least making it easier for traffic to access State Highway 16 westbound (which will be important post Waterview Connection as the primary route from the North Shore to the Airport), the Port and the Cook Street offramp. Interestingly though, there has been relatively little increase in daily traffic over the Harbour Bridge, with NZTA’s latest monthly traffic update showing just a 1% increase in Harbour Bridge traffic in July 2012 compared to July 2011.
For northbound traffic, the story is a bit different I think. While traffic patterns won’t really settle down until after the Wellington Street onramp is reopened, already there has been quite a few noticeable changes to traffic patterns in the past few months – especially in the evening peak. To analyse this further, let’s step back a while to before the VPT opened. At this time the big bottleneck was where the SH16-SH1 ramp and the Wellington Street onramp (when it was open) joined in with northbound SH1 traffic into just two lanes over the Victoria Park Viaduct. The two northbound lanes couldn’t cope with the volumes, which tailed back through spaghetti junction often back to Gillies Ave.
However, what the Victoria Park Viaduct bottleneck actually did was limit the number of northbound vehicles that could hit the Harbour Bridge at any one time to the capacity of the two lanes on the viaduct plus Fanshawe Street plus Curran Street. With a bit of ramp signalling at Curran this seemed to work quite well and even at the peak of the afternoon peak, northbound traffic flowed fairly smoothly over the bridge at least as far as the Esmonde Road interchange. In other words, the bottleneck at Victoria Park didn’t allow too many cars over the bridge during any particular hour – which meant that the motorway north of the Harbour Bridge (at least as far as Esmonde Road, I rarely travelled further north than that so can’t comment too much) didn’t get too jammed up.
Once the third northbound lane of the Vic Park Tunnel was opened earlier this year, everything changed. Many more cars were able to get through each hour, which meant that the Harbour Bridge now had to cope with three lanes of traffic through the tunnel plus Fanshawe plus Curran. Wellington Street’s closure probably didn’t impact on this much as most of its traffic probably diverted to Fanshawe and Curran – meaning it was joining the motorway anyway before the traffic hit the bridge.
My observation is that the Harbour Bridge has coped with this increase reasonably well. I remember reading through the documentation that accompanied the Victoria Park Tunnel proposal and a lot was said about the project resulting in the capacity of the bridge being fully unlocked and utilised. The bridge is slow, but it moves – and that’s pretty good for a piece of infrastructure that really should be squeezed as hard as it can be – given the eye-watering costs of another crossing. The issue is mainly with further north, as on most days it seems there are now stopped cars tailing back a lot further – not just north of Esmonde Road now, but in fact frequently right back to the old toll plaza near the Stafford Road offramp.
My point here is not necessarily to suggest that the Victoria Park Tunnel was a waste of time, but rather to highlight that by removing a bottleneck in the motorway system it has allowed many more vehicles through that pinch-point than before, and as a result it has put a lot of pressure on another part of the network. This means that all users of the motorway have not necessarily benefited from the Vic Park Tunnel project:
- Those travelling from the city centre to parts of the North Shore beyond Onewa Road in the evening peak may well have seen their trip times lengthen due to greater congestion on the northbound side of the Northern Motorway
- Same for those travelling from Curran Street, who have also seen the ramp signal “wound back” to let through fewer vehicles to stop the harbour bridge from getting jammed up
- Those travelling from Onewa/Esmonde to parts of the North Shore further to the north in the PM peak may well have also seen their trip times lengthen
I do wonder whether, in the cost-benefit analysis of projects like the Victoria Park Tunnel, all these negative travel time impacts are taken into consideration as well as the positives. I do think that on balance the project has probably made a positive difference, but remember it did cost around $400 million and is , according to SAHA, 2-10 times better value for money any of the other RoNS. If some of the VPT’s benefits are a bit dodgy, I hate to think how easily the other projects could fall over (for example Waterview Connection feeding a heap more traffic onto the already congested SH16).
On the bright side, more congestion on State Highway 1 northbound in the PM may well just encourage more people onto the busway. Now if only NZTA had bothered to build a bus lane through St Mary’s Bay to carry the 35% of people at peak times passing through the area on a bus, instead of five general lanes of traffic and absolutely no bus priority at all (even though this is meant to be part of the Northern Busway).