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  • Writer's pictureGrant McLachlan - New Zealand Herald - Column

Worst highway junction just got worse

The Transport Agency hasn't factored into calculations how dangerous the Warkworth congestion is.

With the passing of Auckland's Unitary Plan, Warkworth's notorious State Highway 1 intersection at Hill St just got worse. The plan has rezoned the rural area to the north of the intersection to allow for as many as 2200 new residential homes.

The rationale behind such a decision is a narrow-minded belief that other roading projects will fix existing congestion issues. The rezoning has, instead, piggybacked the new roads and choked any chance of bypassing traffic getting through smoothly.

Two such roads have been called "the western collector" and "the Matakana link road". The western collector has been labelled a Warkworth bypass but it zig-zags through the rezoned southern growth cell, which will allow as many as 4300 new homes. The Matakana link road between State Highway 1 and Matakana Rd will dissect the 2200-home northern growth cell.

What makes the rezoning delusional is that the Auckland Council had information from the NZ Transport Agency and Auckland Transport engineers showing that the road projects wouldn't fix existing congestion but decided to go ahead anyway and make the situation worse.

The whole situation is farcical when traffic engineers gave evidence showing that their proposals wouldn't work, local politicians argued that they will work, and ministers threw hundreds of millions of taxpayer money at the problem to demonstrate that something is being done.

We run the risk of so much money being wasted that there is no money left over to actually fix the problem.

The Transport Agency set up a website for "SH1 Warkworth intersection improvements" and allocated between $20 million and $100m to that goal. A photo of the Hill St intersection even features on its header. So far, it has spent a pittance on the state highway and theorised the benefits of the western collector.

Part of the western collector works has begun, connecting Woodcocks Rd with Falls Rd via Mansel Drive. That road is effectively funded by financial contributions from resource and building consents along its route.

The Auckland Council will collect $6514 for each additional lot in transport financial contributions, which equates to $45 million from just the growth cells along the proposed collector roads. But the council hasn't spent the money it has already got from developers to improve roads between their development leading to the Hill St intersection.

The Transport Agency shouldn't fork out money for a road that isn't a state highway and won't benefit the state highway, especially when the Auckland Council will receive money that should pay for it.

I empathise with the Transport Agency. It ought to be able to focus on completing the northern tollway bypassing Warkworth and leave the intersection for Auckland Transport to sort out. Because tollways must have a state highway alternative, it is stuck with Hill St and has to fix it.

To get resource consent for its tollway, the Transport Agency presented evidence showing that, by the time it finishes it, local traffic growth at Hill St would have grown by more than the use of the tollway. Most of the traffic using the tollway will turn right towards Warkworth.

That evidence already warned that the western collector would quadruple traffic along Hill St towards the state highway intersection. What the Transport Agency hasn't factored into its priority calculations is how dangerous the congestion is. Police, ambulance and fire services are regularly stuck when responding to serious crashes at Dome Valley, less than 5km up the road.

Hill St should be a priority. I found 19 intersections with less traffic and congestion that have been upgraded to interchanges in the past decade, costing between $5m and $50m each.

Warkworth residents should get used to that term: interchange. With the most recent traffic data and projections, I've been testing a plethora of intersection formats, including a double-roundabout design, using the modelling software that the Transport Agency uses.

The only format that works is a state highway overbridge with a large roundabout beneath. Such a design minimises disruption because the new intersection can be built next to the existing one.

Traffic disruption will, however, be a major problem at the Hill St intersection when the other roading projects are being built. The Transport Agency predicts an extra 300 truck and trailer units per workday, all turning right through the difficult intersection.

The intersection can't be avoided. It is a major hub serving the town, hinterland, region and nation with few practical alternatives. Putting everyone's heads together will fix this headache. All it needs is everyone reading from the same page.

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