Keith Rankin: Motorway Follies
by Keith Rankin
17 March 2006
I am a committed advocate of the completion of the western orbital motorway. It is absolutely necessary for the sustainable economic growth of Greater Auckland. Principally, it will be a freight highway rather than a commuter highway, linking the many employment-rich parts of Auckland with each other, and creating a number of new zones that people will commute to rather than commute from. Public transport is not a viable alternative to this particular project.
There remain only two segments (both part of SH20) for which construction has not yet started: Manukau City by-pass and the much more contentious "Avondale extension" that links the southwestern and northwestern motorways.
In order to minimise the financial cost (which is distinctly different from the larger economic cost), Transit New Zealand and the Auckland City Council have chosen the Waterview - Pt Chevalier route for the Avondale extension, and have told us that this motorway segment will probably have to be partially funded by user tolls.
The problem with tolls is that roads are public goods. If you charge people to use public goods, then the lost benefits are greater than the reduced costs associated with less usage of the facility.
This means that a tolled motorway is economically inefficient. Just ask the people in Sydney about their underused new Cross City Tunnel. The Sydney authorities are choosing to close a number of alternative routes to force vehicles to use the new toll road.
Tolling the new SH20 by-pass motorway would be especially foolish because its purpose is to relieve Auckland of the multi-billion dollar social costs associated with having present levels of through traffic use Spaghetti Junction.
The only sensible economic argument for tolling motorways in Auckland is to tax specific segments whose overuse creates excessive social costs. Specifically, the motorway segments that would qualify for such tolling are the parts of Spaghetti Junction that are only used by through traffic, such as the bit between the Cook Street off ramp and the Hobson Street on-ramp, and the "Hamilton" on ramp at the city end of the Northwestern motorway.
It would be unreasonable to place a toll on these roads immediately. However, once the western orbital route is completed, then, in order to reduce congestion in the central city area, tolls could sensibly be placed on peak-hour traffic that uses Spaghetti Junction for purposes other than going to or coming from the central business district (CBD). Revenue from these tolls could help offset the financial costs of completing SH20.
That brings us to the next critical issue. The western orbital motorway will not be able to function as an orbital cross-city route if, at critical points, it coincides with roads that link the central city with the suburbs in which city workers live.
With the Waterview route for SH20, the motorway will coincide with the already busy Great North Road between Avondale and Pt Chevalier. And it will coincide with the most congested part of the existing northwestern motorway, between Pt Chevalier and Te Atatu.
If the Waterview leg of SH20 is built, every morning and evening rush hour city by-pass traffic will have to fight its way through commuter congestion on SH16 and Great North Road. SH16 west of Pt Chevalier will become gridlocked.
On the other hand, if the Rosebank route favoured by the Auckland Regional Council (see NZ HERALD STORY) is adopted, then there will be only one short piece of existing road that will become such a bottleneck; that between Patiki Road and the Te Atatu interchange. Extra lanes on that short segment of SH16 should be enough to resolve that problem.
I am concerned that there has not been enough planning imagination gone into the more coherent Rosebank route. I am also concerned about the environmental damage that will take place around Owairaka's Hendon Ave and the Alan Wood Reserve whichever route (Rosebank or Waterview) will be chosen. And I am concerned that one of Auckland's most significant multicultural institutions and source of cheap groceries – Mt Albert's Pak'n'Save supermarket – may be demolished. What effect will that have on the communities in the west of Auckland City?
At present, sophisticated tunnelling equipment is being used to solve the huge environmental problems associated with the construction of the Orewa-Puhoi (Alpurt) extension of the northern motorway. Surely it must be possible to adopt much of the same technology, and build twin tunnels under Hendon Ave and Pak'n'Save as part of a Rosebank Peninsula route.
(A Transit NZ representative told me at a public open day that these tunnelling machines are not big enough to construct three-lane carriageways. But the link between New Windsor, which is the end of the Mt Roskill extension, and Te Atatu should only involve two-lane carriageways. At the New Windsor interchange, traffic will divide three ways: southwest to New Lynn, north towards St. Lukes, and northwest towards Avondale and Te Atatu. Thus, it is appropriate that the motorway lose a lane at this junction. Further, there will be fewer problems between Patiki Road and Te Atatu if the new merging motorway has two-lane rather than three-lane carriageways.)
These alternative options (full tunnelling and adopting the Rosebank Peninsular route) may incur higher financial costs to construct than will a motorway through Owairaka and Waterview. The economic costs associated with a motorway that both destroys communities and fails to achieve its basic aims are far higher, however, than the costs of constructing the correct road in the first place.
And let's toll the Spaghetti Junction problem, not the western-orbital solution.