Newsletter #40 - 22 June 2017
Over the past week our team has been busy with preparing our submission to Parliament. After many refinements, today we lodged it. We look forward to speaking to it in Parliament at the end of July.
We were also at the intersection on Friday getting our photos taken for an upcoming TV promotion. Thanks to everyone who honked and waved.
While we were at the intersection, we noticed several things that are the subjects of this issue.
YOU CAN’T DO THAT!
The works at Kowhai Park are well under way. The bridge is in the process of being installed and the kerbing looks close to being poured. The whole carpark area has been fenced off, avoiding traffic disruption.
At the Rodney Local Board Annual Plan consultation at the A&P Showgrounds on Saturday, several members of the public commented, “You can’t rip up the new park for the intersection!”
Oh dear. Yes, Kowhai Park will look great when it is finished. Yes, the works are paid for by overdue depreciation. Yes, the works realised that the intersection might eventually encroach on the carpark. No, that is no excuse to not upgrade the intersection using Kowhai Park.
Central to the intersection’s problem is that it is essentially five intersections within 30 metres. To increase the capacity of the intersection, the intersection needs the space to work effectively.
While watching the traffic at the intersection, it was increasingly apparent the problems between Elizabeth Street and the traffic lights, especially traffic on Sandspit Road turning right onto the State Highway 1 heading north. See if you can spot the problem in this photo:
What’s odd with this photo? Believe it or not, it is a green light for left turning traffic heading south on State Highway 1. In fact, the green light phase was 25 seconds long and yet there were no vehicles in the left turning lane (A in the photo).
Why, you wonder? Because there are two cars at the lights (1 and 2) wanting to turn right and a big blue truck (3) at the Elizabeth Street give way also wanting to turn right at the lights. All the vehicles behind the truck wanting to turn left have to wait for the next right turn green light phase to get the chance to get past the give way and queue in the left turning lane at the lights.
The problem with this is that the right turning green light phase (and straight ahead green light phase towards Hill Street) is only 8-10 seconds long every 120 seconds.
Welcome to 2021. Yup, with all the Sandspit Road traffic wanting to use the motorway when it opens in 2021, they will have to turn right at lights or turn right at the Sandspit Road/Matakana Road intersection to use the Matakana Link Road.
Try turning right at Sandspit Road onto Matakana Road now. That’s the route to use the much-touted Matakana Link Road. Then remember, the Sandspit Link between Sandspit Road and the Matakana Link will be built after 2033.
But this is 2017. When the NZTA predicted the 2026 traffic growth at the intersection for the 2014 motorway hearings, they didn’t expect that those projections would be surpassed in 2016.
The solution isn’t just making the right turning phase longer. Here is a diagram of the fan effect problem, showing how the lanes work between Elizabeth Street and the lights.
Years ago, the Sandspit Road slip lane into Elizabeth Street also allowed traffic to enter the left turning lane at the lights. The existing signage on the corner of Sandspit Road and Millstream Place still shows signs of the old format:
See how a light blue sticker was placed over left lane between Elizabeth Street and the lights and then a white line added between the right lane and the left lane at the lights? The rationale behind those changes was due to the queue of left turning traffic at the lights restricting traffic wanting to turn into Elizabeth Street.
The problem is that Sandspit Road traffic trying to get into the right lane holds up traffic behind it on Sandspit Road wanting to get to Elizabeth Street.
The two lanes are a problem. In an ideal world, we would ask for a three-lane solution, with this configuration:
With the above configuration, the left lane would slip into Elizabeth Street, the centre lane would lead to the left turning lane at the lights, and the right lane would head straight ahead to Hill Street and right at the lights.
Sandspit Road is at capacity and it will get worse. During the November 2016 Elizabeth Street trial, a maximum of 480 vehicles squeezed through the intersection with Matakana Road in one hour. That’s 9000 vehicles per day. By 2026, the NZTA predicts that 18,200 to squeeze through, needing to give way to Matakana Road traffic that will increase from 8000 to 13,000 a day. They’re dreaming.
In the charts below, the intersection is at capacity of ~400 vehicles per hour for most daylight hours.
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