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Do ramp signals really help?

By now we’re pretty well acquainted with ramp signals on motorway onramps across Auckland. You know the ones:

Signals-1-566NZTA explains the reasoning behind ramp signals on this old page (which hasn’t changed since the NZTAs predecessor agency over 5 years ago):

Currently traffic on the motorway is disrupted by ‘bottlenecking’. This means whenever traffic enters the motorway and then shifts from lane to lane, it creates a slowing pattern as vehicles back up behind the on-ramp entry zone.

Most accidents on Auckland motorways happen during peak hours when traffic is stop-start, due to lapses in driver concentration and motorists travelling down crowded on-ramps vying for positions in traffic or trying to merge together.

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.

Early analysis suggested that ramp signals improved the throughput and reduced the levels of congestion on the motorway:

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 on clip-on lanes on Auckland Harbour Bridge
  • 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

The big question with ramp signals has always been whether it just “shifts the problem” onto the local roads. When ramp signals were initially introduced, Transit NZ was an agency solely focused on the operation of the motorway system and didn’t really care what happened on the local roads. As long as the congestion wasn’t on the motorways then it wasn’t their problem. NZTA has (fortunately) taken much more of a one network/system approach to transport in Auckland than this and work very closely with AT in the day to day management of the network. 

I suppose the big question is whether the improvements to flow on the motorway network are sufficient to counter-balance the additional waiting on onramps and on the local roads that lead to the onramps. But more deeply, I think there are questions around whether we want idling cars (and their pollution) on local streets where everyone else is, or confined more to motorway corridors away from where people live, work, walk or cycle. Do we really want to privilege long-distance trips (those already on the motorway network or who access it at more distant onramps where the ramp signalling doesn’t happen or is on a faster cycle) over shorter distance trips from more central locations who get stuck on really long queues at the signals? These are all complex questions.

My gut feeling is that ramp signals are probably a good thing on balance providing they are actively managed to ensure:

  • they aren’t in operation when they shouldn’t be.
  • they respond to problems on the local road network.
  • any benefit to the operation of the motorway network really does outweigh the impact they have on the local road network.

However I’m not sure if we are currently getting all of those benefits, in particular the impacts on local roads. Some of those impacts are bound to part of the reasoning for monstrosities like Lincoln Rd.

53 comments to Do ramp signals really help?

  • Greg N

    “Some of those impacts are bound to part of the reasoning for monstrosities like Lincoln Rd”

    And also the widened St Lukes Road Overbridge which along with widening of the motorway is some $70m, and I’ll bet a large part of that is no doubt making the overbridge wider.

    – the local board member who oversees transport issues reported this week in this blog that the widening of the overbridge was primarily “to allow stacking of turning vehicles”.

    And stacking is needed why? Because the motorway On-Ramp signals just down the road cause tail backs on to the ramps onto local roads and prevent the normal right turn phases from working as intended.

    So we have another case of solving one problem, but causing lots more problems downstream.

    On the whole while the motorway does seem to run better once you’re on it, but you can spend a long time waiting to get on it, and there are more than a few cases where I’ve had to wait at the ramp signals for access to what turns out is a near empty motorway. Which is not at all efficient.

    I also wonder that since that early “success” assessment was done that the CMJ was undergoing and has had quite a lot of work completed on it to improve throughput, so how much of the “success” was actually due to ramp signals and how the other stuff? Hard to say now, but maybe a second followup assessment is needed to see how its panning out.

    And in any case, traffic soundbound in the AM peak over the bridge and through to Greenlane will no doubt be enjoying the “NEX” effect which as reduced cars on the bridge at peaks times substantially And also do not forget the “peak traffic” situation we are now some 8+ tears into. all will improve flow as the number of vehicles (especially cars) reduces, the flow (and throughput) will improve.

  • Sailor Boy

    Queuing is awful around Tristam Avenue in the morning. It ruins the whole area when lots of people are trying to access local schools and businesses blocked by the motorway queue.

    This seems especially peculiar as the on ramp simply goes onto another lane on the motorway

    • GrantB

      Problem with Tristam is a classic issue of the on-ramp being too close to the Takapuna/Northcote road off-ramp.

      So people pouring on at Tristam and ending up on the left most lane, are trying to move right into the middle lanes at exactly the same time that people are trying to move left into the lane to get off at Northcote.

      It does cause pain though – my wife works north of Milford, and could in theory use Tristam and take the motorway north in the mornings, but the southbound queue + various rat runners makes it too difficult.

      I take Northcote road, then head south across the bridge, and the array of rat-running techniques on display there are breathtaking (and scary).

      I think the ramp lights do work (have seen it when lights are off and very slow moving traffic tries to push into the motorway) but in the end, the problem remains too many cars at peak time. Things like Skypath and better integrated bus system will result in bigger long term wins.

  • Sanctuary

    It just shifts the problem. For NZTA, it improves motorway flow. For the poor muggins drivers who pay for all the extra kit and caboodle of lights and cameras (you and me) it does nothing to improve commute times, since they just spend more time waiting on the local roads to get onto the motorway. So for actual punters, it is just a colossal waste of (their) taxpayers money. I would like to see the spend on these lights vs. cycleway expenditure….

  • bbc

    They seem like an expensive waste of money, something which NZTA appears to have too much off. How about spending that money on things that actually need improving such as cycling, walking and PT. Until then, IMO they’re just a way for NZTA to burn off large sums of money and achieve very little. People will still lack alternatives, NZ as a whole will continue to get fat and unhealthy and the health system will suffer. Stop rearranging the chairs on the Titanic.

  • bbc

    Imagine what the $70 million being spent on widening the already existing overbridge and motorways would achieve if spent on a mode which has at present nothing i.e. cycling. Auckland’s priorities really are quite depressing and I really see no light at the end of the tunnel in terms of the vast sums being literally wasted to achieve nothing. Liveable city? Seriously?

  • SteveC

    it was pretty widely recognised at the time of introduction that the ramp signals were only shifting the problem to the local roads, but one of the ironic effects of ramp signalling at the Greenlane interchange is that the queue back from the south facing onramp blocks the offramp traffic, causing a tailback onto the motorway itself, own goal

  • George D

    They do work. Vehicles move efficiently at slow speeds, because you can only put so many on a high speed road before they jam (overcompensating). The real answer is to put variable speed limits on motorways to decrease speeds and optimise throughput.

    They’re also very cheap – the opposite of current NZTA spending, where higher budgets make a project more attractive to the agency.

  • Luke C

    The other interesting issue is they encourage longer distance commuting at expense of short distance. For example benefit people from Kumeu, Sliverdale and Pukekohe who don’t have to deal with ramp signaling, as they get on the motorway before it starts. Therefore their journeys are made much quicker, compared to someone stuck at Massey, Manurewa or Sunnynook. This could be seen to encourage sprawl.
    Of course bigger issue is negatively affects PT, as buses get stuck in congestion from ramp signaling. And on the Southern Corridor only a handful of buses on motorway, so do not benefit from reduced motorway congestion.

    • Greg N

      And some, like the on-ramp at SEARTSH1 northbound allow trucks over 3.5T and T2 vehicles, bus taxis, motorcycles unfettered access to the motorway irrespective of the ramp lights there.

      Ever wonder why theres always a big jam northbound just after Mt Wellington On-ramp heading north? – well the SEART on ramp truck/T2 lane is the cause.

  • Jon Reeves

    After living in Europe for another 3 years, having travelled through 34 countries since 1996, i have not seen these pathetic on ramp signals anywhere else. Including countries that experience far higher levels of traffic like France, Uk, Germany. I think they are a waste of time and do just push the problem onto local roads effecting the lives of thousands of residents.

    And apart from higher local pollution levels, at what financial cost for installing and maintaining them? I remember the initial set up cost around $70 million. Now it’s expanded must be $100 million wasted.

    You could easily ditch them and us the cash for extending electrification to Tuakau!

    • Greg N

      mind you I’d never seen traffic lights on a roundabout until I drove on some in the UK, so each to their own I suppose.

    • JenL

      Interestingly Jon Reeves, we thought the same thing, then went to the UK just last month. We noticed they do now have motorway ramp lights as well. I don’t know how new they are, but they have them on a number of the major motorways.

  • Jon Reeves

    But, by virtue of the fact, other countries do not use ramp lights could give you a clue they are regarded internationally as unacceptable solutions to congestion?????

  • nick1234

    Yes, there were certainly quite a few in the UK when I lived there, although that was ten years ago so maybe they’ve been phased out since.

  • Stuart

    The one area where these have worsened the effects of bottlenecking is the Onehunga on ramp onto SH20. This always clogs up and clears straight after the onramp.

  • “But more deeply, I think there are questions around whether we want idling cars (and their pollution) on local streets”

    That’s the point I make when some raise the issue of slowing traffic on Nelson and Hobson streets. Impeding the flow of traffic to/from the motorways only creates issues for the surrounding areas, in particular increased pollution.

    • Sailor Boy

      How could you possibly slow the traffic anymore?

    • V Lee

      Not sure what you are trying to say here. It is idling queues of cars that cause more pollution. Free-flowing traffic moving at 30 km/h isn’t going to cause more pollution than free-flowing traffic moving at 50 km/h. A lower speed limit will also not increase congestion at peak time either (when no one can travel at the speed limit anyway).

  • V Lee

    I think they certainly work for their stated purpose – which is increasing throughput on the motorways. They also certainly increase congestion on local roads, although not quite as bad as you would think as the increased motorway throughput does seem to mitigate this a little bit. It is a trade-off with all the stated negatives, more pollution on local roads, more benefit to people living further away etc.

    I’m also not sure NZTA is really monitoring them properly as they promised when they were installed. They seem to be on a lot when traffic is free flowing and when that its hard to see them helping at all. They are also on when it is completely pointless – ie when the motorway and on-ramps are so congested that the cars released by the lights to travel a couple of metres and rejoin the queue in front of them on the on-ramp (although of course this isn’t really causing any harm, it just looks really silly).

  • Jon Reeves

    They certainly DO NOT exist in major cities l travelled around in the UK, France, Italy or Germany …. And in the past 3 years living and working there l travelled to countless cities.

    These things a plain bollocks. They don’t work. Time travelled from point A to point B is just the same except you sat in a stinking traffic jam on local roads paid for by ratepayers.

    • That really depends on where your A and B are. They quite obviously favour long trips that spend most of the time on the motorway (say Manukau to Albany), over shorter trips where you spend most time queueing to get on (say Gillies Ave to Khyber Pass).

      They undoubtedly do work in terms of what they are designed to do, which is keep traffic flowing on the motorway. Now whether that is worthwhile given the problems they cause on surface streets is a different question.

      Now I don’t drive at peak time very often at all so perhaps not one to comment, but I do remember commuting by car before they were introduced. My memory of that was on ramps and their approach roads would gum up all the same, as the motorway got clogged around the merge points and neither the motorway traffic nor the ramp traffic would go anywhere in a hurry. I’m not sure if it is really any different now. What is the difference between waiting at a ramp meter queue or an un metered ramp tailback? In both cases the motorway is operating at the limit of capacity and can only admit about the same number of vehicles at each point.

  • JimboJones

    My trip from Newmarket to Mt Roskill almost doubled in duration thanks to Kybher Pass and Gillies Ave being clogged by these signals. I’m sure the people in sprawling suburbs were better off, but those of us that don’t need to get on a motorway definitely paid the price!

  • Kent Lundberg tweeted this link recently, which includes a cute video demonstration of bottlenecking and how pacing resolves it: http://www.strongtowns.org/strong-towns-podcast/2013/1/24/show-124-rightsizing-streets-with-gary-toth.html

    Incidentally, the link also includes a podcast discussing the more general notion of “right-sizing” streets (i.e. not always down-sizing or widening, but finding the right size). This works out for regular streets on the same principle as ramp signals for highways.

    • Greg N

      Thats a very simple video not always applicable to real life – for a start this example covered a “motorway” with a single entry and exit, not an entire motorway system with multiple entries and exits and lanes and differing traffic speeds.

      In addition, the demonstration assumed you had perfect control of the input/flow rate to maximise the throughput and also assumed that you could “store” the cars without problems completely out of the (motorway) system until they could be released (in the video case, you hold the rice in the beaker as long as its needed until it was ok to be tipped into the funnel.).
      So its a theoretical (and some would say, economists) solution to the problem:

      Its major drawback is a given grain of rice in the beaker could not predict its end to end journey time – apply that to the individual car driver – would they or you find that acceptable if you could not determine how long it will take to travel from A to B with some reliability over multiple journeys?

      In theory if you had perfect traffic monitoring on the motorway BEFORE each bottleneck/on-ramp you could allow only sufficient cars to enter it to ensure the flow was maintained.

      However, that would then cause horrendous backlogs on the on-ramps at some locations as you have to hold cars back to maintain flow rates and does privilege existing users of the motorway (who are on it already) over new ones.(who want to enter it).
      Yes you can reduce the flow/upstream “pressure” by letting less cars on upstream, but that, like water released from dam and flowing down a river takes time to arrive, causing frustration and more gridlock on local streets in the meantime.

      We do not have such fine grained monitoring in the Auckland motorway system nor do we have a proper way to “store the cars” until they can be released except as limited length dual lane on-ramps that can “Store” about 20 cars each.

      Once the cars are on the motorway they have to continue to flow or the system stops working, so to bring in this sort of pacing you have to control every entry to the system and tight monitoring of the entire system at each point and as a whole.

      In Aucklands case, this would include removing those T2/Truck lanes at SEART/SH1 Northbound and SH20 going South.at Onehunga as they permit traffic to bypass the pacing completely and simply load the motorway up, as well as controlling the traffic flowing from SH16 to SH1 and SH20 to SH1 as well – its no good managing SH1 well if when the SH20 traffic turns up it all turns to custard -which is why they put lights where SH20 merges with SH1.

      However, that video did show (indirectly) a solution, which is the current “only way” used to solve the problem by our traffic planners – and that is you fix the issue if you “make the funnel wider” – yes doing that improves throughput at that point, but not necessarily overall and is expensive to do.

      But in the absence of any real political will to manage the situation better, its seen to be the “easy” solution used a lot..

  • Richard Horner

    Ramp lights are the daftest idea imaginable and goodness knows how they can work out their advantages.
    As suggested above the problem for merging traffic is that the designers of the system have built too many interchanges too close to each other. Ramp lights will never solve this problem which can only be solved by closing half the ramps. Ramp lights were trialled here in the late 1970’s at Esmonde Road Takapuna and within weeks of installation Transit or its predecessor were told by Takapuna Council to turn the stupid things off they were clogging Lake Road up half way back to Devonport!! The lights went and the poles stayed at the side of the ramp for months as a memorial….. Suddenly a new generation of traffic engineers and without research/trial the lights pop up at almost all Auckland’s ramps.

    I thought it was illegal to place traffic lights and obstructions on motorways? Where the NW Motorway? meets the Southern when heading south at Manurewa you sweep round a gradual right hand bend then suddenly three lanes of motorway have ramp lights. A massive nose to tail must happen here. A motorway merging with anther motorway is not an on ramp and i suggest this set of lights is illegal and dangerous

    • V Lee

      Well there are no laws about putting traffic lights on motorways, so definitely not illegal. It is all policy and since NZTA makes up the policy then I guess they get to decide what is an on-ramp and what isn’t and where they can put the lights. I’m also pretty sure there isn’t a major problem with these light causing nose-to-tails. You’re really concerned about laws and what is legal I see so I’m sure you always drive in a legal manner with sufficient gap to the car in front. Which will mean there is never any danger of you crashing if the cars in front of you have to stop at any of these lights. So not illegal or dangerous but perhaps still a bit daft for other reasons.

  • Tamaki

    I tend to ignore these lights and go when they are red. What’s the penalty?

  • Richard29

    I would second the comment about encouraging sprawl by privileging traffic already on the motorway. At the time the ramp signals came in I was living in Glenfield and my co-worker was living near Silverdale. My journey time got longer and his got shorter, I really dislike the ramp signals and he thinks they are great!

  • I spent a significant amount of time investigating the Ramp Metering system when they were introduced as the first one was trialed in Mangere Bridge.

    One of the main benefits proposed by the Ramp Metering system was the future introduction of road tolling. The infrastructure has been laid to rapidly deploy road tolling equipment. Road tolls will be very controversial if it is ever introduced across the Auckland Motorway network.

  • Richard29

    @Tamaki I suspect that the main penalty for running the ramp signal lights, if you do it regularly, is that NZTA will just assume a certain level of cheating and will change the cycling of the lights accordingly to hold back all the other drivers slightly longer and ensure the same flow of traffic onto the motorway. Your commute becomes a tiny bit shorter at the expense of everybody else from your on ramp waiting a tiny bit longer. So basically the penalty in most cases is the same as most other instances of rule breaking and queue jumping – your fellow drivers may not feel you are ‘driving social’.

    • You can only cheat from the front of the queue mind. If they were to slow the rate to account for cheaters, those cheaters would just spend more time getting to the front of the queue.

      • Tamaki

        Unless more people cheated, then they might have to weigh the costs of enforcement against the benefits of the scheme. I notice then when i run a red, the cars behind me also seem to follow me quickly. Civil disobedience can be contagious.

  • Richard29

    Also – pet peeve. Why are do the ramp signals at Tristram and other places not indicate which lane has preference to go first when they merge? You have this weird situation where two card are merging from a stopped position over a very short space of time in a kind of mini drag race. Either you slam your foot on the gas and try and get out ahead or you hold back and let the other car soar ahead, but you don’t really know what approach the other driver will take so either you both take off really slow until one driver takes the initiative to speed up, or more often both cars take off at speed only for one of them to have to slam on the brakes in order to merge properly….

  • Richard Horner

    At last thanks to Toa we hear the real reason for these stupid lights. It makes sense that if the motorway system is tolled then some electrical control / measuring device is fitted to the on ramps….. Thank you Toa

  • George D

    Non Motorist said it best above. Usually the comments here are quite supportive of evidence based policy making.

  • Ari

    My impression is that they generally work for the shoulders of the peak times. But i’m not sure NZTA manage them closely enough because I think the ideal speed is ~70kmph, but often the motorway is running much faster than that.

  • JohnP

    Ramp signals are worse that simply shifting delay from the motorway to the onramps. Regularly the queue extends back to a point where it blocks the cross roads so people in cars and sometimes buses cant get under the motorway. That means severance isn’t just a pedestrian issue it affects so called faster modes as well. North Shore City made Transit NZ sign a protocol that they would turn off the signal whenever the queue made it back that far. But of course the two newer4 agencies, AT and NZTA don’t bother with that any more. I am happy to be mocked as a high priest of traffic flow. But ramp signals are heresy and someone needs to be burnt at the stake over this debacle. The proponents have never measured delay on the side roads or ramps in their statistics they publish! Getting rid of ramp signals would be the biggest easy win in Auckland transport.

    As an aside to show how Economic Analysis can throw up weird results the B/C to turn off all ramp signals would actually be negative because positive transport benefits would be divided by a cost saving which is a negative cost (not additional benefit). positive B divided by negative C gives a negative B/C ratio. Isn’t rigid policy analysis grand!

    • Greg N

      This is my gripe – they have never actually properly measured the full impact of the Ramp Signals across the entire network. Its all be done on some ones “say so” that it works.

      All NZTA can actually say is that it makes the motorway traffic flow faster.
      They can’t say anything else and AT don’t seem to hold NZTA to their word about ensuring no local street issues which was the big concern when it came in.

      Everyday I see Alpers Ave at the Broadway end clogging up right into and across the intersection, the incessant honking of horns by frustrated drivers who can’t move for other blocking the intersection makes you feel like you’re in New York not Auckland. This is solely due to the Ramp signals holding back traffic on local roads.

      It actually gets so bad now that half the Manukau Road & Gt South Road traffic can’t move past the Alpers Ave intersection as their exit from the intersection is blocked.
      St Marks Road on-ramp has similar issues and sometimes these two local motorway on-ramp tailbakcs combine in one Gordian knot of traffic.

      How can this actually be called an improvement when Newmarket grinds to a halt each day from about 4pm for 2+ hours?

      • JohnP

        Exactly the same created congestion occurs at Constellation Drive. Sometimes they leave the things on when there is almost no traffic on the motorway. Changing things is hard enough in this country but when public servants make a mistake like this you can’t get them to change things back until the people who made the mistake have died. It is just like the left turn giveway rule. Ramp signals makes a mockery of all the planning processes that are supposed to avoid remedy or mitigate effects. Just before it came in I was at the Environment Court and Judge Smith criticised ramps signals for delaying people who live closer to town thereby encouraging people to live further out. The Transit NZ national manager claimed he was mistaken as the delay would only be minor the goal was to simply alter the arrivals profile at the merge. Well that was BS.

        I have even met people who run it who are appalled.

  • Dave P

    I still for the life of me, do not understand the need for motorway lights when the lane is NOT a merge lane. Per example, Mt Wellington north and south on-ramps. Both dedicated lanes. The lights serve no purpose what-so-ever apart from holding traffic on local roads.
    While at this location, why is this still just 2 north and 2 south bound lanes restricted by the bridge widths?
    I seriously doubt the new south-western via waterview will make that much of a serious impact on traffic via this pinch-point.

    • JohnP

      Yes it makes a mockery of their claim that it was all about arrival profile at the merge point. It is more about providing a one off time penalty on traffic joining the motorway system. Then there is how it is run. How often do we see hardly any traffic on the motorway say level of service B and cars being stopped repeatedly on the onramp. That even happens on a Sunday at Upper Harbour southbound onramp. Feel free to ignore anything NZTA says about traffic flow or capacity so long as they run this system.

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