20 Viaduct Harbour Avenue Auckland 1010
Private Bag 92250, Auckland 1142, New Zealand
Ph 09 355 3553
Fax 09 355 3550
7 April 2022
Sam Alavi
[FYI request #19046 email]
Kia ora Sam
The information you requested - CAS-536096-P9S1Z5
I refer to your official information request dated 4 April 2022 regarding the traffic lights at the
intersection of Domain and Parnell Road turning into Ayr Street.
Attached to this letter is the Controller information sheet (CIS) for the Parnell Rd, Domain Dr, and
Ayr St intersection. The CIS is a technical document that the signal designer wrote to specify to the
software developer how the traffic lights are to operate. This document is unlikely to be understood
by anyone without traffic light expertise and so excerpts are taken from the CIS and explained
below.
Intersection layout
For reference, below is a schematic diagram of the traffic signal hardware and phasing at the Parnell
Rd, Domain Dr, and Ayr St intersection. This is not to scale:
aucklandtransport.govt.nz
Traffic light phasing
The intersection is made up of two off-set âTâ intersections, but for traffic signal purposes it is one
intersection controlled by a single traffic signal controller. That is to say that the lights at the two âTâ
intersections never operate out of synchronisation.
The intersection operates using 4 phases of traffic signals, labelled A to D. The phases are shown above
and explained:
A Phase: Northbound and southbound traffic on Parnell Rd has green lights. Vehicles cannot turn right
from Parnell Rd onto Ayr St. Vehicles will be allowed to turn left from Parnell Rd onto Domain Dr
dependant on whether a pedestrian is crossing Domain Dr. Pedestrians can cross over Ayr St.
B phase: Northbound traffic on Parnell Rd has a green light. Vehicles can turn right from Parnell Rd
onto Ayr St. Vehicles will be allowed to turn left from Parnell Rd onto Domain Dr dependant on
whether a pedestrian is crossing Domain Dr.
C phase: Vehicles can turn left out of both Domain Dr and Ayr St. Vehicles that have turned left out of
Domain Dr can either travel north onto Parnell Rd or turn right into Ayr St.
D phase: Vehicles can turn right out of both Domain Dr and Ayr St. Pedestrians can cross over Parnell
Rd.
The phases run in alphabetical order, and A phase must run in every cycle of traffic lights. The phases
are triggered by vehicles waiting on different approaches to the intersection. If no cars are waiting for
a certain phase, then that phase will be skipped and will not run until the next cycle of traffic lights.
The right turn from Parnell Rd northbound into Ayr St.
There are four sets of right turn arrows that control the right turn into Ayr St. Two of these sets of
right turn arrows are electrically wired in parallel and operate identically. The remaining two sets of
right turn arrows are also electrically wired in parallel but operate differently to the other two.
The two sets of right turn arrows (circled in red above) are green during B phase, and red in all other
phases. On the phasing diagram, this is represented as the number 3 arrow.
The two sets of right turn arrows (circled in pink above) are green in both B and C phases. On the
phasing diagram, this is shown as the number 10 arrow. These right turn arrows follow special logic
for road safety reasons. When transitioning from B to C phase, all four right turn arrows will turn
yellow then red at the same time as the straight through round lights so that all northbound traffic
on Parnell Rd see red lights and red right turn arrows. 4 seconds later, traffic turning left out of both
Ayr St and Domain Dr get a green light, and three seconds after that
only the right turn arrows
circled in pink turn green to allow traffic that has turned left out of Domain to turn right into Ayr St.
It is at this stage that the 2 different sets of right turn arrows have different colour displays.
We hope that this explains the operation of the intersection with specific regard to the right turn
into Ayr St.
Yours sincerely
Rua Pani
Group Manager Auckland Transport Operations Centre
