It’s good to see progress towards a safer city, with Auckland Transport consulting on its next project in the road safety programme:

The Manurewa (Area 2) Safety Improvements project. Submissions are due next Monday 8th March.

At the end of this post, I also outline an alternative approach for future safety projects, which will enable Auckland Transport to achieve much more from the same budget.

The location for this project is immediately south of the first area of Manurewa they implemented last year.

Manurewa was chosen on the basis of need: safety statistics for the area are terrible. The area’s street layouts allow and encourage very high driving speeds, creating the tragic situation that people are being killed and hurt in life-changing ways just trying to move around their suburb. Sometimes it’s people simply out walking. The community is affected in many ways, including that people don’t let their children move about independently, and are put off wanting to walk and cycle themselves – including to the bus and train. This is the cause of many problems: congestion, public health from physical inactivity, and transport poverty for those who don’t drive.

Change in this area needs to shift not just how people drive, but how the streets – and the people using them – are valued.

The project is ambitious. Of Auckland Transport’s safety project areas to date, this one covers the largest area.

As the diagrams above show, there will be a lot of speed humps – 250 apparently – and other treatments to help calm traffic, which is partly because the area is so large.

In designing this project, Auckland Transport had the benefit of the feedback from the first Manurewa project, in which many people said they wanted the area extended.

What’s great to see is the local leaders supporting the project, as reported by this article in the NZ Herald:

People will says it’s overkill, says Manurewa Local Board chairman Joseph Allan, but if it saves one life in the community it is worth it.

“Safety is seriously important for our community. When you have cars travelling through the area at 120km/h something is going to happen and lives will be lost,” said Allan.

With the backing of the local board and local councillors Angela Dalton and Daniel Newman, AT has selected Manurewa for the largest traffic calming programme in Auckland…

Each stage is costing $4 million…

AT says the measures will help to create a slower speed environment, saying the area of the second stage had 131 crashes in the past five years and vehicles travelled at more than 120km/h on Rimu Rd, McDivitt St and Coxhead Rd.

The push to slow down traffic arose around 2017, said Dalton, from concerns in the community over speeding, police chases and rat-running in an area with six or seven schools.

“It looks good, it’s definitely safer and it can only but slow people down or they damage their cars. We know it is safer around those schools. The safety for those kids was paramount.”

She said the schools are grateful for the changes and, so too, families with children but acknowledged the community is divided.

Newman said Manurewa’s roads have historically had some of the worst serious injury and death rates of anywhere in Auckland.

“It really upsets motorists who don’t like a slow drive and speed bumps, but there is a significant safety element to the measures. If other communities saw it they would be jealous,” he said.

Barney Irvine, infrastructure spokesman for the Automobile Association, said it is good to see AT changing the roads in Manurewa to bring speeds down, rather than just dropping the speed limit, and more was needed.

“Reducing speeds on quiet residential streets around schools, where there are safety issues, will sit comfortably with most people, and we’d expect it to have plenty of support from locals,” he said.

These community leaders need a hearty thanks for their leadership. Our city needs every elected member to be an ambassador for safety and for decarbonising our transport system. (And good to see the AA taking a more responsible path than they did in the central city, where the complex mess of frequently changing speed limits can be traced back to their lobbying.) 

The Herald also peppered the article with comments from people not wanting to see these changes. Ironically, these people are opposing improvements for drivers. Traffic calming makes it easier to turn, change lane, to look for and manoeuvre into a car park, and easier to see where it is you’re heading if you don’t know the area. Through enabling modeshift, the project can also improve driving for those who need to, by reducing the number of cars on the road.

Auckland Transport commissioned research into public perceptions before and after the similar, but smaller, Te Atatu and Papakura projects. The ‘after’ surveys overlapped with the first lockdown last year, which may have influenced results. Yet they are still striking:

More than four out of five respondents (82%) felt that the speed humps and tables have made the area safer overall, including 50% saying it is much safer than before. The net increase in positive safety ratings was +76%.

Hopefully Manurewa will also be included in the next tranche of speed limit changes (which, incidentally, seem to be running late. There was supposed to be one tranche per year, and the next set is actually just a tidy up of some of the harder-to-resolve roads in tranche one. To catch up on specific commitments Auckland Transport made to the Safety Review, Auckland Transport will need faster action.)

Hopefully Auckland Transport will implement this Manurewa project quickly and move onto the next one.

Of course, there are always improvements to the project to suggest.

First, where’s the safe way to bike on the main roads? On Auckland Transport’s Auckland Cycling Network map from 2015, Weymouth Rd and Great South Rd are shown as “existing connectors” – but for all ages cycling, they need the cycle lanes protected. And Mahia Rd is a proposed connector. These are critical routes to the train stations, so we can expect to see a lot of new housing in the area. If repairs to the network like this aren’t done now, are they programmed to be done by 2030? In fact, does AT even intend to return to the area and set it up for safe, low carbon transport by 2040 or 2050?

Secondly, there are too few pedestrian crossings. All the entry treatments and side roads need pedestrian crossings so people can walk freely along main roads and cross safely every time they meet a side street. Along Mahia Rd, for example:

And there need to be more pedestrian crossings over the main roads too, and much closer to the intersections where they are shown. The safest way across a road needs to be at the same location as the easiest way across – and evidence shows ensuring this is so improves safety considerably. Here, all the crossings are too far away:

Auckland Transport knows how to follow its own design manual and find a way to get them all closer, respecting pedestrian desire lines and accessibility needs. They managed much better at Franklin Rd:

In many places the cost of nearby speed bumps would be better used to shrink the size of the intersections:

Finally, there’s a better approach to traffic calming that we’d prefer Auckland Transport to use for future projects.

This would involve dividing the area into low traffic neighbourhoods, where walking and cycling are easy. Vehicles can still access each property – but there is no through-route that allows rat running. By eliminating those shortcuts for people racing to save time, and cutting the long roads into shorter sections so speed can’t be built up so easily, far fewer speed bumps are required. This frees up budget for other improvements.

To illustrate this idea, I’ve split the area into three walkable and bikeable “low traffic neighbourhoods”, where vehicle traffic is only from local movements – meaning it’s light, and occasional.

This isn’t the only way the area could be split up, and people who know all the different ways Mountfort Park is used will know where the best division between the blue and yellow neighbourhoods should be. I’ve chosen Sykes Rd, but that can be changed. Mountfort Park needs to accommodate both safe walking and cycling, as well as access for vehicles to each carpark.

For the other division, between the yellow and orange neighbourhoods, I’ve used Coxhead Rd, which is a good boundary because it’s a bus route. The other bus routes through the area, on Rogers and Christmas Rds and Glenveagh Park Drive (shown in red), are better kept within the neighbourhoods.

Next I looked at where you could install “modal filters”. These can be made from anything, like planter boxes, bollards or rock walls. Some filters allow people, bikes, scooters and animals to go through, but not general traffic, like this one in Freeman’s Bay:

Some filters allow emergency vehicles, rubbish trucks and buses using rising bollards or enforcement cameras, and the location can be decided tactically:

Image credit: Citymobility

Here’s a modal filter in Mt Eden:

There are dozens of different arrangements of locating the modal filters, and this would all be decided through local community engagement. Below is one possible solution, demonstrating how few modal filters are required. For this arrangement, perhaps ten filters would be needed. The seven shown, plus maybe three in the park.

In addition to these ten filters, entry treatments would still be required. And these should be more than just red paint. Some entry treatments may allow traffic in only, or out only, like this one in Grey Lynn:

Something like this treatment might work, as proposed in Cambridge:

Safety changes proposed by the community and adopted by the Waipa District Council.

Since everyone driving in a low traffic neighbourhood is going to a local address rather than cutting through to save time, the need for so many speed bumps melts away. Extra traffic calming measures could be added in as required, perhaps using timber in a tactical way, like this idea from Napier

An Innovating Streets project for traffic calming in Napier. Image credit: RNZ

Or chicanes could be used. Eventually, these could accommodate trees, like in this Ponsonby street:

With a budget of $4m, the project had enough money to do all this and experiment with different technology for the modal filters – including rising bollards or camera enforcement of modal filters. And there would still be budget for improvements to the public realm, protected cycling on the main roads, and allowing a larger area to be covered.

Hamilton street calmed with kerb buildout. Image credit: Dr Bex

The Manurewa project must proceed without delay, largely as it stands. The safety improvements are urgent. But if you agree the low traffic neighbourhood concept is a good way forward, could you add that to your submission? Ideally, Auckland Transport would produce a city-wide masterplan, based on an analysis of traffic circulation on the boundary roads. This would allow individual low traffic neighbourhoods – designed by communities themselves – to fit within a coordinated plan.

Low traffic neighbourhoods across the whole city can be a cornerstone of our safety and transport decarbonisation planning. 

Families use the Carlyle Road modal filter

Image credit: Cambridge Cycling Campaign

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109 comments

    1. Low numbers of people walking is a good sign of dysfunction, Christopher. Residential areas should have loads of pedestrian traffic, especially near schools. This project will hopefully help fix it.

      1. +1000 – that intersection is surrounded by housing. Lack of pedestrians is a big flashing red light, not a reason to do nothing.

  1. Really all depends on the speed hump design chosen. If they are the short sharp nasty ones then all they do is damage vehicles with excess wear and tear while increasing emissions (wasted energy braking then accelerating again) and generating noise for nearby houses.
    If however they are the more gentle smoother ones then they can achieve reduced speeds without many of those negatives. They’re also often cheaper to build and result in less road maintenance later. Better for buses and cyclists too.

    1. Speed humps built in Auckland have been sinusoidal for a decade or more. Any ones you may have seen that don’t comply are either old, or on private land.

      1. Are pedestrian tables the same? The Elstree Ave/Pt England roundabout ones were brutal for anything that doesn’t have high-riding suspension. They may have been fixed or changed in the most recent works programme as there’s been a lot done to the roads out there lately and I haven’t been out there in a while, but they were brutal enough to warrant remembering.

        1. The ones that are on Streetview seem like modern tables, so can’t really say whether you are referring to them or to an older style that may have been there before, sorry.

          Also – and I’ve got some mixed feelings on them – many of the recent tables are built as Swedish tables (i.e. steep upramp and gentle downslope). This also assists reducing any comfort issues (with a slight impact on traffic calming effect particularly on roundabouts, which is why its not 100% positive – but overall they are good).

        2. Taking the rail replacement bus out to Sunnyvale a couple of months ago, I noticed raised pedestrian crossings in a few places that were gentle on the way up, and steeper on the way down. The effect seems to be for the driver to slow in time for the way down (and much less slowing in time for the pedestrian crossing itself.) Any idea why these have been installed? Are they just around the wrong way?

  2. Combining this with the speed reduction is very important. Takes away the opportunity to jump on the anchors in your race car and then accelerate as hard as you can up to 50km/h and then jump on the anchors again and complain that your car uses more fuel. If all the speed humps in a area are designed for 30 or 20 then the limit should be that.

  3. The easiest traffic to slow down is the traffic that is no longer there. This would be a great area for low-traffic neighbourhoods.

    1. The difficulty of course is that you DO have to provide alternative travel options – chicken and egg complexity. Otherwise all you could be creating is a more car cul-de-sac designs.

      This doesn’t mean that I oppose LTNs, especially if they mainly concentrate initially on cutting off some larger-volume through traffic routes. But we really need to work on this holistically. People in Auckland drive because we have made it the only viable option for many – it needs carrot AND stick. Again I’m not saying Heidi isn’t envisaging this, just need to keep in mind that its a complex topic needing many levers moved.

  4. Great piece Heidi. Really enjoyed reading that.
    The Manurewa Local Board should be applauded for their leadership on this. I’m the Captain of the ‘Hate on LBs’ Brigade. What i think might be interesting to watch is how these ‘Non NIMBY Suburbs’ (for lack of a better term) leap ahead in terms of liveability and genrally public pride in where people live.

    What Manurewa is doing is fantastic and you can see in the not too distant future being a far more vibrant and inviting communities than the Nimby enclaves of Remuera and Parnell that have very ‘car first vibes’. The next challenge then of course will be to guard against the socially regressive cancer that is ‘gentrification’. That is a subject for another day.

    Go for it Manurewa! Have fun, enjoy, design, take back your health and the safety of your community!

    Set the example and hopefully the rest of the Local Boards will want a piece of that!

  5. Speed humps are an archaic way of dealing with the issue, but they show the desparation of the local board,to get AT to address the safety issues in the area.AA support is odd ,as well. I guess the innovative thinkers never get to positions of influence in any public organizations or lobby groups.Once again walking/cycling ignored,apart from potentially slower traffic,that is not accelarating between speed humps

    1. The reason vertical traffic calming is used is because the roads built in the second half of the 20th century across most of Auckland are far too wide. Proper slow-speed street design requires much narrower roads. But changing that restrospectively is ENORMOUSLY expensive. That 4 million? You probably could narrow (at least in a proper, BAU way) maybe 10%-20% of the same treated area. Sure, you could do localised narrowings with trees and planter boxes and so on at much reduced costs, but that creates is new pinch points for people on bikes.

      And the full-on street redesign can financially only really be done for when we (for other/combined reasons) do a full street rebuild after all – or in greenfield new subdivisions.

      For the rest of the city, In my view it’s traffic calming or dead pedestrians. Even blocking through traffic in an LTN doesn’t get rid of SOME dangerous speeding unless you combine it with traffic calming.

      So to say this is all about how no innovative thinking is used is unfair in my view. This is a massive issue physically cast in (kerb)stone over decades. Overcoming it will take a long time (which isn’t a reason to go slow on it, admittedly).

      I do wonder whether we should put speed limiters in all cars. But hey, THERE’s a politically suicidal thing to propose. Status Quo is one hell of a drug.

        1. Well, wide streets certainly provide opportunities, like implementing cycleways because there’s space for tim tam dividers.

          But if we’re looking for cheap traffic calming that doesn’t go as far as removing all the kerbside parking, wouldn’t wide streets allow this option, Max?:

          Local narrowings using planterboxes or blocks that are set out from the kerb. This gives bikes have a bypass, and they also need to slow, but don’t get forced into the main path of the vehicles?

        2. Its potentially feasible, but as we found in Northcote, having cycle bypasses often just results in people parking in a way that blocks them. It’s very difficult to get everything working together. I’m not saying that planters and build-outs should be out – but I AM saying that vertical traffic calming is the most effective method on many of the key factors.

  6. Modal filters with S shape street is preferred over too many speed bumps.

    The problem with speed bump is cars will decelerate and accelerate frequently.

    In Manurewa many people still drive old cars instead of hybrid. The older cars can be quite noisy and polluting during acceleration.

      1. The difference is they can drive smoothly in slow speed when the street is S shape, compare to fast slow fast slow

      2. Except the people you really want to slow drive low slung cars that can get through a chicane faster than the speed limit. Humps really screw with those guys. They have hard suspension and hardly any clearance so if they go fast on a hump they break plastic bits off their pretend racing cars.

  7. Was cycling with the whanau through that exact area of Napier shown in the photo just last week. Very impressed with the cycling infrastructure in Napier and the hinterland.

  8. Great post, Heidi. $4m doesn’t go as far as some people think. Spending some of it on more expensive features would mean losing many cheap features. Yes, the thresholds should be better, but raised crossing tables would cost a lot. They may need to follow along with main-road walking and cycling projects. Good interim thresholds seem most suitable now.
    Modal filters are still obstructed by the legislative framework. Innovating Streets may help us to get through that barrier (so to speak). As Heidi has shown, this are could make very good use of them – later if not now.
    The total number of speed humps is irrelevant – this is a big area. What counts for people is the number they have to cross making their normal journeys and (rat-runners apart) that is not too many for any household.
    Sinusoidal speed humps have been found to be comfortable enough on local bus routes in the other LTN areas, providing the bus driver knows what they are doing.
    Cheap features are important to cover large LTN areas. Modal filters would be reasonably cheap once they are an accepted tool.

    1. Thanks, Streetguy. On the legislative thing, none of the arguments I’ve heard have stood up to scrutiny.

      Any chance you’ve got to the bottom of the problem and can explain what’s happened legislatively to change the situation since all the modal filters that were implemented throughout Auckland and New Zealand in the last 30 years or so? And why other councils are managing to put them in now?

      The other question I’d like to pose to AT is, if this really is a legislative problem, why did they have modal filters in their advice all this time without bothering to sort it out?

      1. It’s so obvious that we need modal filters, they need to be in design guidance. I don’t think any one Council is willing to pay the cost of taking a case to court to defend and overturn the precedent. But now Innovating Streets is pushing ahead with them, I expect Waka Kotahi will lead the legal issue through. And about time too.

  9. “The area’s street layouts allow and encourage very high driving speeds,”

    Are you able to elaborate has to how the current street layout encouraging very high speeds? If you define 50km/h as a “very high speed”, however I fail to see how it encourage people to drive any faster than that.

    Regarding the Franklin Rd roundabout, I actually find that design rather dangerous, particularly for pedestrians and cyclist on the downhill side.

    1. Just checking the existing operating speeds here.
      It seems most of the local roads currently have a mean operating speed of 25-30km/h.
      The collectors are in the range of 40-45km/h.

      Don’t think I’d class either of the above as “very high speed”.

        1. Nice trolling.

          I was simply pointing out that there the vast majority of road users here don’t seem to be speeding.

      1. > Don’t think I’d class either of the above as “very high speed”.

        I would.
        Where do you find this data?

        1. You class a mean speed of 25-30km/h on a 50km/h road as “very high”. We are talking car speeds and no pedestrians here.

          This is GPS speed data from TomTom.

        2. Yes, I class a mean speed of 25-30km/h in residential streets as very fast. These streets are designed like racetracks not residential streets, so the speeds are understandable.

    1. This study is hilarious: “changes in speeds due to acceleration and deceleration, are the main sources of vehicles emissions”. The logical conclusion from this claim is the ideal state, from an emissions perspective, is traffic which never stops. This is clearly what we must aim for, no decelerating and accelerating. So never do any traffic calming or anything to discourage driving through residential neighbourhoods, maximise it, but never allow it to stop… beautiful clean perpetual motion never polluting and never arriving… amazing how you can find evidence for absolutely anything if you discard enough context.

      Clearly fewer vehicle movements however they are driven pollute less. But if we start from the assumption that traffic can never decrease we can tie ourselves into impressive knots over tiny details.

        1. Why do you find the idea of speed humps so offensive?
          Why do you insist that speed humps inevitably waste fuel?
          This very much depends on how you drive.

          If I know a slow-speed-zone is coming up or if signage advises me, I will gently slow down ahead of any humps.
          As I approach the hump I will lift my foot off the accelerator and let the vehicle engine-brake down to the appropriate speed. If the slow-speed-zone continues with successive humps I will try to maintain the “hump speed” or accelerate only minimally between humps. No need for brakes. Once clear of the low speed zone I will accelerate gently away.
          Fuel used? Probably no more than negotiating an equivalent speed-limited zone that doesn’t have humps.

          And if driving a vehicle full of passengers this makes for a far more comfortable ride than unnecessary braking and accelerating.

        2. Dave B
          It sounds like you would be quite a hazard on the road if you maintain the same 10-20km/h speed needed to navigate the speed bumps. This would likely result in frustrating other road users resulting in people overtaking you on residential roads. Most cyclists and even the occasional runner would be passing you.

          Note: If I found the idea of speed humps offensive I wouldn’t have said the following.

          “Now I’m not saying I don’t support speed bumps anywhere in the world, they do have their uses. In many places they likely have very little impact on emissions as they simply divert the traffic away. “

  10. Good to see that AT has finally adopted the Area-Wide approach to traffic calming which The Albert-Eden Local Board has been doing since 2014. Faced with widespread and unfair criticism in the media which suggested that this was a waste of money and would make no difference, the Board commissioned a post-installation traffic survey. Ten points for which we had speed data prior to building the Balmoral-Sandringham LATM scheme (about half the size of Manurewa Stage 1) were surveyed again about 6 months after construction. To our surprise the average before-and-after speed reduction was 23% (ranging from 8% in the previously slowest road up to 36%). The 85th percentile speeds reduced from being in the range of 45-59 kmph to being in the range 30-45 mph – i.e. from having over half over the legal speed limit to all of them complying with the limit . The key feature of our scheme was to treat the area as a neighbourhood, rather than just a collection of streets, with all entrances off neighbouring arterials having a painted threshold treatment and explanatory “slow zone” signs. I am very pleased to see that AT has begun using the thresholds but think that they need to add some simple signage (not speed roundels) to encourage reduced speeds, noting that well over half the users of these streets are local residents who should be easy to persuade that they and their children will be the main beneficiaries of quieter and safer roads near their homes.

    1. Yes, area wide treatments are far better. The Te Atatu South and Rosehill, Papakura monitoring of modeshift is also really encouraging – and can be followed up to check how Covid L4 impacted it.

      A sign saying “No Through Route” because there actually is no through route, would definitely be more effective at reducing *traffic volumes* than a red paint treatment at an entry where there is a through route. And the LTN evidence suggests it would be better for reducing speeds and encouraging modeshift.

      The next piece of information we need is the long term effect of each type of calming. The UK LTN monitoring includes some good long term data, and it’s impressive. When I requested it, I found there was no long term monitoring of the AELB schemes, which means we can’t tell how much behaviour change initiated by the visual cue of red paint may have been lost due to familiarity with it over years. I assume they would’ve followed up with me if it has now been done.

      Is that something you could request, Graeme?

    2. Yes area wide treatment is a real innovation for AT. Just like Auckland City Council did in Ponsonby in the late 1980s or One Tree Hill Borough did in the early 80s.

      1. haha, innovation is just consultants bringing back stuff from decades ago that everyone forgot about, but giving it a new fancy name so it sounds new and innovative.

  11. I have been having another think about this,everybody has a gps(smartphone),& google will send you on the route with least traffic,as it will think it is going you a favour,getting you there faster.therefore speed humps are just as likely to induce more traffic.If vehicles were filtered out,google would get the message

    1. The evidence is strong that these apps have caused huge increases in traffic volumes on small residential roads in the US and UK. Anecdotally it seems to be true here too – we just don’t monitor the traffic on the smaller roads so well. The apps work by calculating the travel time, so IF speed humps slow the trip down a bit, the app will prefer other routes, relatively, so there’ll be no traffic induction.

      In fact, speed humps are actually unlikely to slow the trip from one side of Manurewa to the other appreciably; they’re more likely to smooth the speed out over the journey. Whereas most people think about there being lots of deceleration before a speed hump, followed by acceleration, the reality is that without speed humps, people tend to accelerate after intersections, travel fast, and then decelerate to the next queue at the next intersection, and then sit idling.

      Low traffic neighbourhoods, on the other hand, definitely change the directions given by the direction apps, because the routes through the neighbourhood are blocked to vehicles. So they tell drivers to use the main roads. The effects are astounding at reducing traffic, improving air quality and enabling people to walk and cycle. A recent tweet with good data:

      https://twitter.com/clairekholland/status/1367060486282436610?s=09

      1. That’s interesting about the Railton study. I hope they post similar results for the other LTNs they’ve implemented in Lambeth.

        The methodology they’ve developed for establishing the mid-Covid baseline looks reasonable, but I hope they do a follow up once Covid is clear. Depending on the vaccines and variants that may not be far away.

  12. The Napier photograph was where the shooting happened last week. Also its a pity the Cambridge wasn’t our Cambridge but good example. Our Cambridge is a lovely town now we just need to connect up the rail again. But then again all those old towns in the Waikato are nice.
    Suppose I better say something about speed bumps and raised tables. They sure slow down those lowered cars with big exhausts and loud speakers. Some of them need to go over them on an angle so they don’t ground out.

    1. The first Cambridge example is our Cambridge and the second Cambridge example isn’t. And yes, those planters are a pretty example, I think.

  13. Those filters are such a no brainer, not sure why they muck around with speed bumps when a filter can remove most of the traffic. It can also function as a small community park.

  14. Of course the quick and cheap way to allow us all to have safer residential streets would be to lower speed limits. 40 (or lower) should be the default on non arterial roads, apply that to the entire city ASAP.

  15. What, if any, research has been done into the possible increase of greenhouse gas emissions caused by these “calming” measures?

    Also, if the speed limit is 50kph how can these “calming” measures be legal?

    1. Trolling. Somehow, slowing down vehicles, and encouraging walking and cycling through better safety is claimed to caus greater greenhouse emissions – just because someone argues that by speeding up immediately after a speed hump petrol use increases abovbe average for a few seconds, and then extends that to claim extra for the whole journey with no evidence. Also, properly designed area-treatments avoid (severe) up-and-down speed changes by getting people to stay in a lower band all the time.

      And that is the “speed limit”, not the “minimum speed”.

    2. Why wouldn’t they be legal? There are plenty of sections of 100kmh road where these speeds can’t be reached due to ‘calming measures’ such as mountains and river gorges, I don’t believe these gorges have been outlawed.

    3. I posted this above

      “Januševičius and Grubliauskas [18] found rising concentrations of CO2 and NOx near the speed humps and bumps with increments from 1 to 8 times for NOx, and from 1 to 5 times for CO.”

      https://www.mdpi.com/2076-3417/10/5/1592/htm

      It however is classed as trolling as it triggers the anti-car brigade.

      1. OK, so that is a simulation. The question is what speeds did they assume? From what I can tell they don’t mention a speed limit at all which is highly dodgy.

        1. I’ll admit I only skimmed it (for now) due to lack of time, so I couldn’t see speeds either. Was it the extreme example of “floor it, slam on the breaks, floor it again”?

        2. Did you try reading it? The particular link mentioned numerous studies for which only one, or some, were simulations.

          It’s simple logic that speed bumps would increase fuel usage, and based on that emissions only have one way to go. Factor in most engines are less efficient/clean under load and you also get emissions from breaking it is all pretty self explanatory.

          The only counter argument I have heard is the claim people don’t slow down for speed bumps and they just keep rolling along at a constant 10-20km/h. If indeed people didn’t slow down for speed bumps then there would be no point in having them.

        3. “The obtained results showed an increase in the concentrations of NO, NO2 and CO found in the pollutants emitted from the vehicles approaching speed bumps/humps compared to the concentrations of the same types of pollutants at the check points. As for trapezoidal speed humps, the concentration of nitrogen dioxide increased on average by 1.8 times, that of nitrogen monoxide by 4.3 times and that of carbon monoxide by 2.2 times. Meanwhile, the concentration of nitrogen dioxide at circular plastic speed bumps rose on average by 2.5 times, that of nitric monoxide by 5.0 times and that of carbon monoxide by 3.2 times.”

          https://link.springer.com/article/10.1007/s11869-019-00683-y#:~:text=Speed%20bumps%2Fhumps%20can%20increase,(Haworth%20and%20Symmons%202001).

        4. The first one doesn’t take any account of real world effects such as traffic evaporation and modeshift. Does the second one? I can only see the abstract which doesn’t give enough detail on methods.

          In the real world, traffic calming reduces emissions and improves air quality, because it affects how people behave.

        5. Heidi
          I think you need to take a step back and ask the question, why do people travel?

          The answer isn’t “I don’t have speed bumps on my road therefore I like to spend my days driving around needlessly”

          Rather the reason people travel is because they want to go somewhere.

          Placing a bunch of speed bumps on a residential street that isn’t suffering from through traffic isn’t going to suddenly result in everyone going, “Oh, I don’t think I’ll drive 20km to the beach, or 10km to work, no I will go for a 2km walk and then come home and bake some muffins.”

          In the context of a quiet residential street, adding speed bumps isn’t going to result in an 80% reduction in travel from the people living there.

          Now I’m not saying I don’t support speed bumps anywhere in the world, they do have their uses. In many places they likely have very little impact on emissions as they simply divert the traffic away. However its ignoring the science and reality to claim the 100 to 800% increase in emissions in these areas will be offset by a 90% drop in car usage.

        6. There’s 2 questions about that figure?

          – Which maximal speed did they assume? I.e. do cars in their simulator speed up to some set speed or do they keep speeding up until they have to brake for the next bump?

          – How fast did those simulated cars go over a speed bump?

          Yes you have to take a step back and ask why people travel. But the next step is “why do they travel by car?” The answer is quite often “because the current design of the streets makes other options infeasible”. That last thing is the problem they are trying to solve.

        7. “100 to 800% increase in emissions in these areas”

          From speed humps. Lol. Reality check, Richard.

        8. Mum-of-two:
          Obviously you didn’t bother reading either of the links I provided and you’re just trolling.

        9. Just point out where those numbers are then.

          I would expect some level of increase in emissions — but not by a factor 8 — and this is balanced by the fact that people are less likely to do all their trips by car.

          Some of it will depend on how many people are dumb enough to floor it after every bump. And also on how well AT builds those bumps. IMO they should be OK at 20 km/h so you can slow down slightly from a speed limit of 30 km/h.

          Maybe AT will measure whether pollution actually increases or decreases. If they don’t we’ll never know for sure. The worst pollution doesn’t happen on those streets anyway but on busy highways and arterials.

        10. roeland
          You seem to be rather dismissive of scientific information for something that is about as obvious as gravity.

          One would assume that if people were doing research on speed bumps they would look at typical situations and not introduce all sorts of random criteria to make their research irrelevant.

          “The answer is quite often “because the current design of the streets makes other options infeasible”. ”

          I highly doubt that is “often” the answer. I think it was rather evident from the Level 4 lockdown that the factor that influences people’s choice in mode of travel the most is the distance they are travelling. I certainly don’t choose to drive to the North Shore from Papakura because the current design of the streets makes it infeasible for me to walk. I also don’t choose to walk to the shops because I have a speed bump nearby, nor do I choose to ride my bike on the weekend because there is a short stretch of protected cycle lanes.

        11. Roeland
          “Just point out where those numbers are then.”

          You mean like what I quoted from the article I linked in my very 1st post on the subject?

          “Januševičius and Grubliauskas [18] found rising concentrations of CO2 and NOx near the speed humps and bumps with increments from 1 to 8 times for NOx, and from 1 to 5 times for CO.”

          “this is balanced by the fact that people are less likely to do all their trips by car.”
          Care to explain your logic as to why installing some speed bumps on a residential street will stop someone who currently drive 10-20km to work from doing so anymore? Or why they will decide to walk 5km to the supermarket?

          “The worst pollution doesn’t happen on those streets anyway but on busy highways and arterials.”
          That’s the same argument people use to say NZ shouldn’t do anything to reduce our emissions because China makes more. 

        12. Roeland
          Click on the link provided, they are right there. The link references multiple research papers on the topic.

        13. I scanned the report because the exchange made me wonder if Richard was being straight up.

          The numbers are there in section 2.1, 2nd to last paragraph, last sentence.

        14. You may use 800% more fuel for the 100 milliseconds or so that it takes for each axle to climb onto the hump. Beyond that, any additional fuel used is entirely at the discretion of the driver and the way he/she chooses to drive.
          And you can avoid using any additional fuel as you climb onto the hump if you simply coast over it and allow its natural retarding effect to be a part of your speed-control regime.

        15. Section 2 is the related work, and it shows there’s significant spread between estimates. There happens to be one mention of 1 to 8 times increase for nox. So there’s your 800%. However most estimates are much lower.

          Anyway. The max speed is implied in section 4. They have a 7.5m cell size with max speed of 4 cells per second. 30 m/s or 108 km/h.

          So if you’re planning to put speed bumps on the motorway you have been warned.

        16. Roeland
          You seem to be very obsessed over the model and ignoring the real world tests, why is that? Are you trying to hide from the science?

          “Januševičius and Grubliauskas [18] studied the impact of speed bumps and humps on emissions of CO2 and NOx. They measured emissions with mobile laboratory equipment at five locations with speed humps installed in pedestrian crossings to reduce vehicle’s speed. Speed humps with trapezoidal shape are frequently found at pedestrian crossings, meanwhile speed bumps have semi-circular shape and are more abrupt than speed humps [24,34]. Januševičius and Grubliauskas [18] found rising concentrations of CO2 and NOx near the speed humps and bumps with increments from 1 to 8 times for NOx, and from 1 to 5 times for CO.”

        17. Too many troll accusations. Richard has raised some important points. We need to remember what we are trying to achieve with LTNs. Quality of life in residential neighbourhoods, and travel choice to reduce travel poverty and unnecessary carbon/energy consumption. We need to look for tools that are cheap and effective, with least negative effects. We also need to use them where the will actually make a difference, in conjunction with other measures – especially improved public transport and active mode access to work, education, retail etc. Manurewa should be a place where these other changes can accompany LTN. So speed humps should be used where other measures cannot; should be spaced so that acceleration and deceleration are minimised, to reduce noise and emissions; numbers on any resident’s journey should not be excessive for time and comfort penalties (back injuries or conditions need to be considered for inclusive travel); and should be used to encourage traffic diversion and evaporation, rather than fight a losing battle if poorly planned.
          The reason so many are used around the world is that they do achieve these objectives – sometimes.

        18. Well you posted a link to a paper about a simulation. What do you expect is going to be discussed?

          The 1 to 8 figure comes from the related work. You can find the full text of Januševičius and Grubliauskas here:
          https://www.researchgate.net/profile/Tomas-Janusevicius
          /publication/332128976_The_effect_of_speed_bumps_and_humps_on_the_concentrations_of_CO_NO_and_NO2_in_ambient_air/links/5d1c3ad3a6fdcc2462bae268/The-effect-of-speed-bumps-and-humps-on-the-concentrations-of-CO-NO-and-NO2-in-ambient-air.pdf

          They measured it, pollution indeed increased a lot, unfortunately they don’t seem to have written down the speeds.

          However they mention something else in their introduction: you increase pollution merely by reducing speed from 50 to 30. Cars just aren’t efficient at those low speeds.

          Anyway we’re playing the long game. That is less km done by driving cars. Make sure that if you go for only a few km (that is a lot of people) you actually have the choice of riding a bicycle. No rat runs — it becomes now a few cars at 30 km/h versus a queue of cars standing still in congestion. Lots of moving pieces.

        19. Roeland
          So I provide a link that provides multiple different sources, and you choose to essentially ignore them all. And now based with zero information you are claiming that by sticking some speed bumps on a residential street we will reduce car travel by so much it will negate all these emissions? I would really like to know your thought patern behind this theory.

          From the proposals I have read in this post we are doing two things, forcing cars to take longer detours and concentrate on main roads therefore increasing congestion and emissions, and forcing cars to decelerate/accelerate multiple times significantly increasing emissions all so we can achieve some percieved safety gains.

          In my view a street should be self explaining, in the following examples the road could be posted at 80km/h yet people would still choose to only drive in the range of 30km/h simply due to its good design.
          https://goo.gl/maps/Nu9CoBepNMbscSXD7
          https://goo.gl/maps/3JiEWuJRpoFGb5NcA

        20. Yes that is the ideal case. I would also rather have that instead of wide streets with speed bumps.

          However Matt mentioned narrowing the roadway is expensive, so it is a pragmatic solution for our bazillion kilometres of existing stupidly wide streets.

          The increased pollution on the main arterials is indeed there. Ghent implemented a plan to eliminate all through traffic in the city centre, and they observed that while pollution in the city centre went down, it went up on the ring road. It is always give and take.

          But this sort of diversion will be part of the plan anyway, whether we go for the narrow roadways or the speed bumps.

        21. roeland
          So you agree then, speed bumps do increase fuel consumption and emissions and are therefore counterproductive when it comes to the goal of reducing our transport emissions?

          This is not to say they aren’t effective at reducing speeds mind you. However as I noted above, the mean speed on these particular roads is 25-30km/h based on GPS travel data and therefore it would appear there is little to be gained and a lot to lose in this particular situation.

          Regarding cost, I would say installing a choke point every 100m would be the same cost as installing a speed bump every 100m. And the argument that these make it less safe for cyclists is based on the assumption that you don’t install cycle bypasses for some reason.

        22. Yes I agree with that, however quoting a number like 800% without the context, or without mentioning it is one extreme for one specific pollutant is disingenuous, the actual number is probably much lower.

          And I initially forgot about it but merely slowing down from 50 to 30 already increases pollution.

          Ideally we’d have narrow roadways, however how do you narrow all those existing ones without breaking the bank. And probably while maintaining parking, because imagine the shit storm otherwise.

          The difficulty with that is that it has to be 100% unambiguous that a given surface is for parking, and never for driving or riding a bicycle. The ambiguity between driving/riding vs. parking is the #1 reason why bicycling is so annoying and dangerous on many smaller streets.

          The Dutch are really good at doing this, you always have different surface treatments and kerb buildouts making it impossible to drive in a parking lane. It would be better described as parking bays.

          The question is can we do it at a large enough scale. Matt mentioned we can’t.

          About chokers without speed bumps, they don’t work. People get used to it and just speed through. If it is a one lane choker it will piss people off. We don’t need more angry drivers.

        23. reoland

          “quoting a number like 800% without the context, or without mentioning it is one extreme for one specific pollutant is disingenuous.”
          You should try reading what I actually said as opposed to what you imagined I said so you can get upset about it.

          “how do you narrow all those existing ones without breaking the bank”
          I mentioned that in my previous post, try reading it.

          “The ambiguity between driving/riding vs. parking is the #1 reason why bicycling is so annoying and dangerous on many smaller streets.”
          This is indeed a unique experience of yours. Can’t say I’ve ever suffered from the stress you mention there. From my experience people are more courteous when it’s ambiguous and get more aggressive as things get more defined. A good example is how angry some cyclists get when a pedestrian is walking in a cycle lane. Or car drivers when a cyclists isn’t using the cycle lane. Another example would be how both cars and pedestrians seem to get on pretty well at courtesy crossings yet pedestrians think they are superman on zebra crossings and walkout directly into the path of moving vehicles.

          “The question is can we do it at a large enough scale. Matt mentioned we can’t.”
          I like how you take Matts word as gospel but reject scientific research that doesn’t support the narrative.

          “About chokers without speed bumps, they don’t work.”
          Do you have some research for this?
          I’ve installed a number of these in multiple location types and all of them have worked based on pre and post implementation speed surveys.

        24. “I like how you take Matts word as gospel but reject scientific research that doesn’t support the narrative.”

          That is a good point, I’m also curious as to why that is. Otherwise you get lot of possibilities, like introducing bends in the roadway by alternating between parking bays on either side.

          The problem with cycling and on street parking is this: You’re sort of expected to go to the left between parked cars, and car drivers may assume you have to give way to them when you have to swerve around a parked car into their path. You get squeezed between those parked cars and driving cars. I don’t know how the road code is interpreted in this case. There was research about bike lanes that also investigated this and it figured out that sporadic on-street parking is in fact dangerous to cyclists. I can’t find the report however.

        25. I agree with your concerns regarding parked cars on main roads, however on residential streets I never had an issue.

          Taking the following as an example, when you come to the cars you simply own the lane as you are entitled to do as a road users. Just like when you approach a roundabout.
          https://goo.gl/maps/PXUvBRng9toNTafg7

          What would make it more dangerous here would be if they kept the on-street parking and then painted some narrow bike lanes right next to the parked cars. This would encourage the cyclists to ride right next to the parked car putting them at risk of getting collected by someone opening the door and it would also encourage the car driver to pass the cyclists as they are passing the parked car. Such layouts have resulted in numerous accidents.

          A better approach would be to remove the parking from one if not both sides of the road, seeing as there is no real need for on-street parking here, and use the new space to create a better facility for all.

        26. As an example near me you can park on almost the entire length of Glenfield Road / Birkenhead Avenue / Onewa Road, which is the main arterial to the city in this area. It is pretty stupid but there it is.

          On a small residential street this clear distinction keeps the roadway for driving as narrow as possible even if parking spots are empty.

          Incidentally that better approach was proposed on Queen Street, Northcote. Turns out you get flamed to a crisp if you remove one side of on-street parking.

        27. “Turns out you get flamed to a crisp if you remove one side of on-street parking.”

          Can’t be as bad as what happens if you suggest speed bumps increase fuel consumption on an anti-car blog, or mention the fact you like the native bush planted around the CMJ.

      2. And once again, Richard fails to realise that increasing the fuel consumed or pollution created by each vehicle on a small section of road does not lead to an increase in total fuel consumption or pollution production.

        1. Once again Sailor Boy makes an ignorant comment in an ironic attempt to try to make himself look smart.

      3. l,m with you Richard ,speed humps should be kicked to touch and modal filters,that prevent vehicular through traffic introduced,there would definetly be an enormous decrease in emissions on these streets, if that is your aim,isn’t this the answer

    1. Not quite as ironic as you however: You pretty much troll me every chance you get whilst accusing me of trolling, no matter how far away my post is from the normal definition of trolling for reasonable people.

      Example: A normal reasonable person would not be triggered by someone suggesting speed bumps increase emissions, and hence such a comment would not be seen as trolling by a normal reasonable person.

  16. Been out this afternoon, checking out the new Manurewa LATM in person. From my observation, although some drivers were alternating between the accelerator and the brake pedals, many (most?) had already adjusted their driving behaviour to a reasonably consistent speed of mid-low 30s (consistent with sinusoidal humps) except on Wordsworth Street and the southern leg of Rowendale (which have the Swedish-style speed tables) where drivers were forced every hundred metres or so to drop their speed even lower and then tended to speed up a tad before the next table. This, and 3 decades experience with LATMs, is why I strongly advocate the Area-Wide approach with “Slow Zone” or similar educative signage at the entry thresholds to make the point that drivers should reduce their speed more or less uniformly throughout the zone – not just when forced to do so when they encounter a vertical feature (hump or table). In reply to Heidi, the Local Board has limited funds so while we paid for one after-match survey to verify that our system works as intended – but we do not plan to spend more of our our precious funds on repeat surveys. But we do think that AT should be doing more such research to establish what LATM features work best and where improvements could be made – especially if they are planning to invest multiple millions in LATMs across suburban Auckland – the draft ATAP [see map on p.14 of the ATAP Stakeholder Discussion document] shows dozens of square kilometres between Te Atatu Peninsula and Manurewa South slated for such schemes over the next decade.

  17. Great post and good they doing something. This is the town our family lived a while back for nearly 7 years including one of these streets on the plans. I agree with your suggestions Heidi.

    1. The issue with them is more that they don’t prevent through traffic. Though the wider ones are definitely nicer.

      1. By “through traffic” are you referring to pedestrians and cyclists? As there is certainly no way a car is getting through that narrow one, and there are bollards to stop them getting through most of the wider ones.

        Why would you want pedestrians, cyclists, scooter etc through traffic?

        1. No, sorry for confusion. Those filters effectively stop vehicle traffic. I should’ve said, “The issue with them is more that there aren’t enough of them. And the wider ones are definitely nicer.”

          I was essentially just meaning what I said in the bottom part of my article – more filters in a full design that prevents through traffic, would do a lot more.

        2. Well the approximately 17 that are already there do a job at blocking through traffic in the locations they are at.

          On a wider scale you need to look at the adverse effects you are creating. From your proposed layout it doesn’t look like to would be too bad as the area is almost all residential and therefore they don’t really block to many trips that can’t easily be diverted. In some cases they do force people to make more dangerous right turns, and they do force more people into the existing busy intersections making them more congested and less safe than they are now but it doesn’t seem to be the end of the world.

          If the area was more mixed use I could see some people driving 3 times further than they did before or simply driving somewhere else.

          Looking at the area it doesn’t really look like a place that would get too much in the way of through traffic, essentially your only really targeting those people who like to take shortcuts through petrol stations located on the corner of intersections, even if it actually take them longer than simply waiting at the traffic signals.

        3. Diverting traffic back onto arterial and collector roads, off local streets is not a bad thing to do. Yes, it does mean intersections and other parts of those roads may need improvements, but they will be good value for money because lots of people will benefit. LTN is mostly about benefit to the people who live in the neighbourhoods.
          Mean traffic speeds are useful for understanding relative before-and-after changes and reasonable “majority” behaviour. But serious harm crashes mostly involve the 15% outlier people, whose behaviour may require physical interventions (chicanes, speed humps, handcuffs).

  18. Many cities already have implemented these plans involving traffic filters to eliminate through traffic. So we can already see outcomes.

    This one from Ghent: (it is Dutch)
    https://stad.gent/nl/mobiliteit-openbare-werken/nieuws-evenementen/evaluatie-circulatieplan-gentenaars-kiezen-vaker-voor-fiets-en-openbaar-vervoer

    People will respond by using the bicycle instead of the car more often. If your trip became much longer due to these filters it is likely that bicycling will be much faster. (It is likely that it was already about the same speed to begin with but heavy traffic deters people from trying it). Ghent measured a 40% increase in cycling within the inner city and 60% increase for people going in and out the inner city.

    1. I don’t doubt they are effective in many cases, that doesn’t mean they are effective where where. For many suburbs, this one included, they are almost exclusively residential meaning that anyone wanting to go to work or the shops needs to travel a large distance.

      As one example of a short trip here, if someone wanted to go to McDonalds it would be about 1.7km trip which is about 3min by car or a 20min walk. Cycling would be about 5mins. Once the traffic filter is in this trip would be about 2.6km and so take about 5mins to drive making it the same as cycling.

      For me personally, that change in distance would have zero impact on my choice as to if I drove, walked or cycled. It would come down to other factors such as if I want wanting to dine in or if I was going someplace else afterwards.

      If however, you put a bunch of these in the CBD along with an area tax, you would likely see a massive reduction in people driving into the CBD.

      1. Congratulations on being completely unique in that you would never change your mode choice, even where the travel time for one mode doubled. You’re very special.

        1. Sorry Sailor Boy, but it seems I’m rather typuical and hence why car travel is so common. Driving any extra 1km in a car is of pretty much zero concern to anybody, other than you so it seems.

  19. “exclusively residential”

    Yes.

    Massive pain point. There are many shops here in commercial zones, segregated from residential areas, whereas in Europe you would find them on the ground floor of a townhouse.

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