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Basin Bridge independent review

Last week we saw some images of what the proposed flyover around the basin reserve might look like. They came about as the proposal is currently going through the fast tracked Board of Inquiry (BOI) process and the board required the NZTA to provide them. Also released along with the images is a peer review of the traffic and transportation related aspects of the NZTA’s application. The outcome of the review is extremely interesting and raises a number of questions not just about this particular project but many others too. The most concerning part of the review relates to how the preferred option was chosen however there were other important issues raised.

The information provided for the BOI process shows that the NZTA had examined quite a decent number of alternatives from different consultants in the past. Opus who were doing the alternatives review for the NZTA narrowed the alternatives down to 5 main options (each with some sub options). These were described as options A to E of which A and B involved the use of an elevated structure – like currently planned while options C and D were at grade options. Option E retained State Highway 1 at grade and raised the local roads over it but was not thought to be feasible.

Basin Reserve Options A-D

Opus then put the various options through a qualitative evaluation and selected Option A as the best one. The peer reviewers say they have attempted to replicate the results and they say that their analysis shows that actually option D performed best. What’s more is that the numbers from Opus suggest that Option D is $25m to $60m cheaper and has a better Benefit Cost Ratio too. So why did option A come out on top? the reviewers have noted the comment “…the differences between the at-grade and grade-separated options in terms of economic benefits and BCR is relatively small for an urban project of this nature…“. In other words it doesn’t really matter about the cost and while Option D had a better BCR and was cheaper yet it it was dismissed as the predicted traffic time savings from Option A were much better. They say this doesn’t mean that Option A shouldn’t have been chosen but it becomes important when considering the next part.

Basin Reserve Options F

After the government started talked about putting Buckle St into a tunnel in front of the War Memorial the NZTA looked at a range of tunnel options for the project. These were named Option F to M with Option F being the preferred one out of that group. It was then compared against Option A but crucially it used different assessment criteria to what was used in the earlier stages. In the assessment criteria the tunnel performed much better than Option A but was dismissed due to the estimated cost of the project. They note (and the emphasis is theirs:

2.17 – In the opinion of the reviewers, Option F provides better overall outcomes to Option A in respect of the criteria it has been assessed against. However, it appears that Option F has not been selected on the basis of it being too expensive to construct.

2.18 – While the reviewers acknowledge that cost is a very important consideration in the evaluation of any project, the weighting assigned to this factor does not appear to be consistent with the approach used to identify Options A and B as being preferred to Options C and D in the evaluation of the initial options. In that instance, the assessment concluded that a difference in BCR of circa 0.5 was insignificant for a project of this scale. Whilst the reviewers do not share this view, the difference in BCR between Option A and Option F is likely to be of this magnitude given the additional costs of Option F and the similar level of benefits generated by each option.

2.19 - The apparent inconsistency and lack of transparency in the underlying process by which options have been compared at different stages of the project is a significant concern of the reviewers.

So cost wasn’t a factor when deciding to go for a bridge vs an at grade option but was a factor when choosing between a bridge and a tunnel.

The reviews go further saying that they aren’t able to double check the actual tunnel costs as the breakdown of them wasn’t included in the report like the other options were. That’s not to say the costs mentioned are wrong but that they haven’t been able to be reviewed.

There was also quite a bit of concern around the pedestrian and cycling facilities being provided. They say:

Whilst the project upgrades existing facilities and provides new facilities to the north, east and to a certain extent to the south, there is almost no provision to the west of the reserve in terms of cycle or shared paths or crossing facilities for pedestrians / cyclists. Cyclists travelling northbound on Adelaide Road who then wish to head west would be required to travel through the Basin Reserve coming out onto the shared area and use the crossing on Cambridge Terrace before continuing westbound through the War Memorial Park. This is a circuitous route compared to following Rugby Street and Sussex Street and is unlikely to appeal to all cyclists. The reviewers observe that the provision for cyclists on the western side of the Basin Reserve is not ideal.

And

Section 7.1.3 of TR4 also assumes that pedestrian and cyclist demand “is forecast to grow at 2% per annum”. However this does not match with Mr Dunlop’s evidence which provides information obtained from the WCC Transport Monitoring Surveys (2009 – 2013) that show a 62% increase over a five year period for cyclists at the John Street intersection (which may in part be due to the Countdown supermarket opening in the interim) and 123% increase over a five year period for pedestrians at the crossing of Buckle Street west of the Basin Reserve.

It is unclear if there is a particular reason for these significant increases. For example, if the increase in cycling demand at the John Street intersection is due in part to the opening of the Countdown supermarket then this may suggest a similar increase could occur on Rugby Street where the consented New World supermarket is to be built. If the future pedestrian and cyclist demand follows the trend shown in the WCC Transport Monitoring Surveys rather than the predicted 2% then potentially the pedestrian and cyclist facilities could be insufficient or under-designed

The evidence of Mr Dunlop also states that pedestrian and cyclist movements could “…double following the duplication of the Mt Victoria tunnel and associated improvements to the existing poor cycle and pedestrian facilities linking the south east”. This, in combination with the recent large observed increases in pedestrian activity in the general vicinity of the project, raise some questions over the suitability of the design of the proposed shared path facility. The reviewers consider the suitability of the 3m wide shared facility should be reviewed in light of the potential significant increases in walking and cycling activity that may eventuate over that currently experienced. Of particular interest to the reviewers is the large speed differential that may exist on the ramp between cyclists travelling downhill and other users, and the lack of escape route for users travelling too fast to avoid a collision.

If the growth in cycling continues like it has then getting the cycling facilities right will be crucial.

All up the reviewers have listed 49 key issues they found with the report, some serious where they are saying the NZTA needs to provide a lot more information though to some which are just a comment but no action is required for. I wonder if we will be able to get the BOI for Puhoi to Warkworth to require a similar independent peer review?

6 comments to Basin Bridge independent review

  • At last, some objective scrutiny of the mysterious ways of the architects of our transport monoculture.

  • I wonder if we will be able to get the BOI for Puhoi to Warkworth to require a similar independent peer review?

    My thoughts exactly. It is great the BOI asked the question, rather than just accept the assertion from the NZTA about the “best” option.

  • erentz

    Sadly with the Memorial Park underpass so far along it seems unlikely now that we can do a tunnel. It would probably require a lot of rework to lower this trench even further and wouldn’t be ready in time for the all important war commemorations next year (the state reason why the Govt funded the memorial park part at the last minute without any real logic behind it was was for this). If there was willingness to adjust the design of the duplicate Mt Vic tunnel as well it could lower the approach into the option F tunnel, making the geometry nicer, which was one of the issues also raised against a tunnel. Of course if you put all the ballooning packages of works together and see that you’re spending a billion dollars, I say screw the whole thing and build an end-to-end deep bore tunnel bypass in one go for SH1 that at the same time solves the problem of the Vivien St traffic sewer.

  • tuktuk

    Great post Matt L, and I hope that this is another milestone toward getting the RoNS (….and some of the current crop of Auckland roads-fest projects) put under greater scrutiny.

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