Beyond separation anxiety: traffic calming & self-enforcing streets

Mar 09, 2016
Beyond separation anxiety: traffic calming & self-enforcing streets

Bike Auckland

A guest blog by Mat Collins, engineer and cycling dad, on quick cheap and local alternatives to fully separated bike lanes.  

Unless you’ve been living under a rock, it’ll be no surprise that the most commonly identified barrier between people and their use of the humble bicycle as a regular mode of transport is the perceived lack of safety. With 60% of Aucklanders saying they would ride more if they felt safer, if we can address those worries we could unleash the huge untapped two-wheeled potential of our city.

Address safety concerns, and they will come.

When you think about improving safety, it’s easy to leap to the conclusion that separating cars from bicycles is the best solution. Roll out separated cycle lanes on every street and surely we’ll be the Copenhagen of the South Pacific, right?

But while separation is often the preferable (and sometimes best) solution, it is also the most expensive – and contentious. This means funding has to be concentrated in a smaller area in order to establish a connected network, and projects get delayed and watered down due to opposition to the reallocation of road space away from cars.

There are other ways to enhance a feeling of safety for the ‘interested but concerned’ potential riders. One solution used overseas to improve both pedestrian and bicyclist amenity on a given street is reducing the volume and the speed of vehicles. This can usually be achieved at a lower cost, while also having greater (and faster) community buy-in than fully separated cycleways.

The idea is that vehicles are slowed and inconvenienced to the point that the street becomes unattractive to most vehicle through-trips, while access for residents is maintained, albeit at slower speeds (which they probably won’t mind, because they live there). So cars are still able to use the street, but they are not given the degree of priority and convenience that they currently experience on most New Zealand streets.

One obvious approach to reducing traffic speeds and volumes is to reduce the official speed limit. Cities around the world, and within New Zealand, are implementing 20 mph / 30 kph speed zones across a network of streets in an effort to improve safety and amenity for all road users.

The non-profit campaign “20’s Plenty for Us” has had quite a bit of success in the UK over the last year, with several cities now embracing 20 mph zones. A 2015 trial in Edinburgh tripled the number of younger children cycling to school, and for older children there was a 7-fold increase, a fantastic result and directly comparable to the two schools recently featured in the Sunday Star Times and Jolisa’s subsequent commentary.

And yet, there’s an argument that reducing the speed limit of a street without redesigning the street environment to encourage lower speeds has little effect unless enforced by the police or road controller. People tend to drive to the speed that the design of a street allows or indeed encourages: so, if you have a straight, wide road with very long visibility distances, slapping a 30 kph speed limit on it is unlikely to actually reduce vehicle speeds.

Hence Auckland Transport’s general stance: because the police do not have the resources to enforce a reduced speed limit, requests to lower the speed limit on residential streets are unlikely to be approved unless streets are self-enforcing.

What does self-enforcing mean? It means designed in such a way that people feel uncomfortable driving over the specified speed limit. In other words, the street itself makes the speed limit make sense.

This can be achieved using a variety of measures, such as:

  • Kerb build-outs to narrow the carriageway, both mid-block and at intersections
Temporary rubber curb extension. (Pic: Wikipedia)
Temporary rubber kerb extension. (Pic: Wikipedia)
  • Vertical deflection, such as speed bumps and raised tables
  • Horizontal deflection, such as chicanes, which interrupt a straight line of travel
Chicanes in Cleveland
Chicanes in Cleveland (pic via Raise the Hammer)
  • Increasing the complexity of the street via measures such as side friction (activity at the side of the travel lane that slows traffic, like street trees and landscaping, parked cars, a line of bollards that narrow the travel lane, queued traffic in the adjacent lane, even rubbish bins on collection day!) and street art, as seen in placemaking initiatives the world over:
Placemaking in Halifax (pic via
  • One-way sections, particularly without explicit priority of one travel direction over the other (this obliges drivers to slow right down to negotiate right of way)
  • Filtered permeability, where sections of a street are made impassable to cars (e.g. with bollards), but allow pedestrians and bicyclists to continue travelling on the street
  • Removing segregating elements such as centre-line road markings (this introduces an element of uncertainty, so drivers slow down and use their judgement about sharing the space)

Treating residential streets in this way, in combination with a lowered speed limit, can give you a bike-friendly (and generally people-friendly) street without the need for fully separated cycleways. [Ed note: Bike Te Atatu has a complete vision of how this would work in their peninsula suburb] 

So where to from here?


If you want to change the layout of your street, it’s important to get local support. The squeaky wheel gets oiled and in a city with 1.5 million, people one voice doesn’t get much attention. Talk to your neighbors about calming your street to make it safer for everyone. Don’t worry about the ‘how’ at this stage; it’s more important to build support around the outcome.

If you find support from others on your street (and who wouldn’t want to live on a slower and quieter street?), the next step is getting your Local Board on side. Local Boards have a degree of influence on AT, and getting their support will be critical to progressing your plans. Of course, it goes without saying that getting involved with (or starting up!) your local Bike Burb group will provide an immediate network for ideas, support and contacts.


The rise of Tactical Urbanism provides a wide array ideas for quick and cheap traffic calming measures. These types of solutions may hit a roadblock (#dadjokes) when presented to AT, so having your Local Board champion these as a trial project may be a more successful approach.

AT also has a set of standard engineering drawings for traffic calming devices (ATCOP Chapter 8); these are obviously more long-term (and more expensive) solutions, and are by no means an exhaustive list of what AT use on a regular basis.

However: don’t feel that you have to come up with the solutions – generating community support for changes to your street far outweighs a full set of engineering drawings that you’ve commissioned yourself!


Local Boards have discretionary funding – and, while it’s not much, they may be interested in chipping in. If the Local Board has all of their funding committed, you can check if your street(s) has upcoming works planned, in which case ask AT (via the Local Board, as a collective of street residents) to include traffic calming as part of the works.

NB Maintenance works generally replace like for like, so Local Board may have to put the thumbscrews on AT in order for the funding for the alterations to be found.

What the future may hold

I thought I’d finish with my favourite piece of local research, The Societal Costs and Benefits of Commuter Bicycling: Simulating the Effects of Specific Policies Using System Dynamics Modeling.

The authors modeled the effect of cycle infrastructure in Auckland and found that, by combining traffic calming on local roads with separated cycleways on arterial roads, Auckland could achieve a 40% mode share for bicycling! Traffic and behaviour modelling is like forecasting the weather one month ahead, widely sensitive to the inputs and only be used as a rough guide, but this is definitely food for thought!

It’s encouraging to see AT’s consultations taking a much wider approach to ‘bikeability’ [ed note: please consider adding your voice to the current feedback about the Inner West suburbs!]  and to hear that these consultations will be spreading across the city in years to come. Finally, we might be getting somewhere.

–Mat Collins

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