I have never been a fan of Auckland’s motorway ramp signals. It all started with a trial in 2004 at the Mahunga Drive northbound on-ramp on SH20 in Auckland and since then we’ve seen them appear all over the Auckland motorway network.
The NZTA website tells us that we need ramp signals because:
“Ramp signalling provides a smoother flow of traffic, minimising stop-start conditions by separating on-ramp traffic into streams of one or two vehicles. Ramp signals are designed to keep traffic flowing on the motorway and to reduce accidents.“
There is also a video to show how it works … unfortunately the link to the video is broken.
On the same NZTA site they quote the following outcomes as evidence that it is working wonderfully.
Data gathered since the signals have been turned on has given the following results for individual sections of the Southern Motorway (SH1):
Curran Street northbound
· Improved northbound traffic flows
· 18% - increase in throughput of vehicles
· 12% - improved peak period travel speeds
Wellington Street northbound and Northwest - North/Port-North
· 6% - increase in throughput of vehicles
· 4.5% - increase in travel speeds
Hobson Street to Market Road southbound
· 15% increase in throughput of vehicles
· 16% improved travel speeds
· Commuter traffic cleared 20-30 mins earlier during afternoon peak periods
· Safer merging and motorway incidents being cleared up to 15 minutes faster, to restore normal traffic flows
Between central city and Ellerslie-Panmure, Mt Wellington and East Tamaki Interchanges southbound
· Peak period traffic flows have been significantly improved
· Shortened periods of congestion
· Motorway is carrying significantly more traffic during peak periods than before
· Travel speeds have increased
I’m not sure how up to date this data is, but I’m not yet convinced. I think these signals add unnecessary bottlenecks to get onto the motorway – especially trying to get into the city in the morning from the Eastern suburbs. It feels like the settings may be overly conservative – I often sit in the queue outside of peak traffic times ready to drag race whoever is next to me while eyeballing what looks like a sparsely populated motorway.
Yes, I agree that ramp signals may improve the flow on the motorway itself – but what about the build-up and waiting that gets pushed back into the suburbs? Maybe the motorway flow is better because there are quite a few others like me who simply avoid the motorway during peak times … or maybe that was the plan all along?
From where I’m sitting ramp meters are installed to restrict the flow of vehicles entering the motorway – or it is “chocking the pipe” … and consequently temporarily storing (accumulating) vehicles on access ways and further back in the suburbs.
That sounds like half a solution to only half of the problem?
I think the priority lanes idea is a better because it actually speeds up flow.
So, here is my challenge to NZTA. Please supply the following on your website:
1. monthly updates of the performance data of motorway flow
2. also measure and show the wait time of commuters who are stuck in the access points to the motorway
With that base data you’ll be able to continuously improve the overall commuter network to become more efficient.
