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The Gauntlet: Issue #27



Newsletter #27 - 23 March 2017

If you haven’t lodged your submission on the indicative route of the Warkworth to Te Hana Road of National Significance, please send it to: warkworth-wellsford@nzta.govt.nz before the end of the month. Our last newsletter (http://bit.ly/2o2i64W) contains the details why the motorway connections for Warkworth aren’t good enough.


(NOTE: This newsletter contains a lot of graphics. To see an enlarged version, please view the gallery at the footer of this newsletter.)


FALSE HOPE

If you thought Sunday’s gridlock was bad, the NZTA’s revised traffic projections don’t offer any good news. The motorway, Matakana Link, and Western Collector aren’t the magic cure that will eliminate congestion. In many ways, however, they will make matters worse.


The NZTA evidence for the Puhoi to Warkworth motorway included these charts:


What stands out to you? Besides the bizarre prediction that travel times won’t deteriorate between 2009 and 2026 (when the table below contradicts this), isn’t it odd that the motorway junction to the north of Warkworth would increase journey times between Warkworth and Wellsford at Holiday Start and between Wellsford and Warkworth at Holiday End?


Currently, Johnstone Hill Tunnels drip-feeds northbound traffic to Warkworth and the Hill Street intersection drip-feeds southbound traffic. Effectively, the Puhoi to Warkworth motorway moves the bottleneck from Johnstone Hill Tunnels to the motorway terminus north of Warkworth.


But the roundabout at the motorway junction does more than that. Northbound Warkworth traffic wanting to head to Wellsford must give way to southbound State Highway 1 traffic wanting to turn right towards the motorway. Conversely, southbound State Highway 1 traffic wanting to head towards the motorway must give way to motorway traffic heading towards Warkworth.


Considering Wellsford traffic southbound to Warkworth has its own sliplane, we conclude that the charts have their labelling back to front.


Minor mistake you ask? Throw in the revised projected traffic growth for Warkworth and the tables turn.


We’ve modelled the revised traffic projections and mapped a typical Sunday afternoon shortly after the motorway opens. With traffic growth, Holiday End peak this year will be like Sunday peak next year, which will be like morning peak the following year. Below is how it will look.



As you can see, the Matakana Link will be at gridlock and so will Great North Road (SH1) between the Hill Street intersection and beyond the motorway junction. Queues on Sandspit and Matakana Roads will stretch to Sharps Road.


“How can this be?” you wonder. Two reasons: First, traffic growth, and second, the design and proximity of intersections. Remember, 2022 is the earliest that the NZTA will start to look at fixing the Hill Street intersection. In other words, it is unchanged.


Ignoring Sandspit Road is decisive. For Sandspit Road, traffic almost doubles by the time the motorway is completed. That traffic squeezes through the confluence with Matakana Road at 400 vehicles per hour, then squeezes through the 100 vehicles per hour right-turning lane at the traffic lights, then proceeds through two more sets of traffic lights at Hudson Road and Matakana Link/Western Collector before it merges with southbound State Highway 1 traffic at the motorway roundabout junction. (Remember, at the Hill Street intersection, it only takes four vehicles on Sandspit Road wanting to turn left at the lights to hold up vehicles turning right - and vice versa.)


Matakana Road southbound traffic will predominantly be turning right onto Matakana Link, holding up northbound Matakana Road traffic. That traffic heading toward the motorway will form two queues at the traffic lights with Great North Road (the current SH1) and Western Collector. Being an x-shaped intersection, the most that will get through an hour would be 900 vehicles an hour, which is much lower than the 1200 per hour that will want to get through. Then the two lanes will merge into a one-lane sliplane to access the motorway, then merge with the southbound State Highway 1 traffic on the motorway.


Some Sandspit Road traffic will want to head towards the Matakana Link, which creates further congestion on Matakana Road.


Here is how Friday peak traffic looks: