The problem with traffic before the lights were installed was the ‘T intersection’ was usually being blocked by northbound traffic on Manukau Road. There are actually 3 lanes which make up Manukau Road. The left southbound lane leading to the intersection use to go straight and the right southbound lane use to come to a stop in order to turn into Harris Street.
Southbound traffic turning right from Manukau Road onto Harris Street would also be sitting in the middle of the road waiting to turn which made this a risk from all three directions.
Now the left southbound lane is used to turn into Custom Street and the right southbound lane goes straight therefore there is no lane to use to turn into Harris Street.
To solve this, the traffic lights have been set up to only allow Harris Street traffic to turn left onto Manukau Road.
Because of the new bus station and park & ride car park being built, the access road Custom Street will see a massive increase of traffic buses and cars. The Council Building access will be closed off from that street and will only be accessible from Manukau Road.
The traffic from Custom Street (especially buses that need to stick to a timetable) would find it difficult to turn right onto Manukau Road because of the through traffic on Manukau Road not having to give way.
I believe that the idea behind this setup will give Manukau Road traffic a more of a continuous flow and will also give traffic on adjacent roads a fair chance of merging.
Parents who drop their kids off that are coming from Stadium Drive or King Street will have to continue on to Massey Ave or down to Glasgow Road if they have already turned onto Manukau Road.