Across the road network there are some locations which we have received high numbers of feedback and comments for. These usually ask why are ramp signals turned on when the motorway appears to be free flowing or that getting onto the motorway is very slow and the onramp and arterial road is congested.
The ramp signal at the State Highway (SH) 20 to State Highway (SH) 1 southbound link is part of a co-ordinated system paired with the Redoubt Road ramp signal to manage the flow of traffic onto the Southern Motorway. The system measures live traffic data as far south as the Takanini Interchange.
These ramp signals were installed as part of the Western Ring Route project to manage the impact of large traffic volumes entering Southern Motorway southbound during the afternoon peak period. When the SH20 - SH1 motorway link was opened the Southern Motorway experienced approximately 9km queues during the afternoon on a daily basis. The introduction of the ramp signals was an attempt to manage this severe congestion. While it cleared this problem, it had the unfortunate and very necessary effect of queuing SH20 traffic.
We observe that the afternoon northbound peak normally starts around 3:30pm and ends around 6pm and usually later on Fridays. The major bottleneck in the area is at the lane drop and merge just after the Hill Road off-ramp. This congestion is unfortunately is not visible to traffic waiting on the Redoubt Road giving the illusion of being on for no good reason.
The southern corridor improvements project has been accelerated and is set to include extra lanes north and south bound from Hill Rd to Papakura. This work, when complete, will mitigate the congestion in both peaks reducing the need for the ramps signals to operate as frequently as the do currently.
Find out more about the Southern Corridor Improvement project(external link).
Find out more about the Western Ring Route project(external link)
This ramp signal works as a co-ordinated pair of signals with the State Highway (SH) 20 to State Highway (SH) 1 southbound link ramp signal. We have activated the signal at Redoubt Road to discourage traffic from SH20 bypassing the queue on the SH20 to SH1 SB link (See FAQ SH20 to SH1 Links (southbound)) and as a control function for southbound traffic on SH1.
It has been observed that traffic exits SH20 at the Lambie Drive interchange, uses Manukau Station Road and right turns into the Southern Motorway via Redoubt Road. The SH20 to SH1 southbound link has a higher road hierarchy thus it has been given a higher priority (but slightly lower than the southbound movement on SH1). The delay at Redoubt Road on-ramp will always be slightly longer than using the SH20 SB link. The frequent use of Manukau Station Road to redoubt Road from Lambie Drive is a queue jumping technique which adds to the congestion on the Southern Motorway if left unchecked.
We observe that the afternoon northbound peak normally starts around 3:30pm and ends around 6pm and usually later on Fridays. The major bottleneck in the area is at the lane drop and merge just after the Hill Road off-ramp. This congestion is unfortunately is not visible to traffic waiting on the Redoubt Road giving the illusion of being on for no good reason.
The southern corridor improvements project has been accelerated and is set to include extra lanes north and south bound from Hill Rd to Papakura. This work, when complete, will mitigate the congestion in both peaks reducing the need for the ramps signals to operate as frequently as the do currently.
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