Traffic control in New Zealand: Guided by the light, or going around in circles?

At NationalMap, we pride ourselves on providing high-quality geospatial data, particularly when it comes to roading infrastructure. One of the key features of any roading dataset for navigation and routing purposes is how intersecting roads are managed.

Most often these intersections are managed just with the classic “give way” or “stop” signs, but with the ever increasing traffic in our urban centres, traffic management systems such as traffic lights and roundabouts are often needed to keep traffic flowing.

As you can imagine, new sets of traffic lights and roundabouts are regularly added to the NationalMap Roads database, but stopping at a newly installed set of lights recently got me thinking, “why traffic lights here and not a roundabout?”.

I don’t have the answer, but I imagine our urban planners have many factors to consider when deciding upon making an intersection “stop/give way”, a roundabout, or opting for traffic lights. 

It made me want to run some analysis on our data and find out what’s the most popular method for traffic management in New Zealand cities; roundabouts, or traffic lights.

While we have previously published data and analysis on the number of New Zealand towns with the most roundabouts, this time, I wanted to look at roundabouts VERSUS traffic lights.

The Numbers: A City-by-City Breakdown

As shown in the graphic below, our analysis uncovered quite a disparity in the distribution of traffic lights and roundabouts across New Zealand's main centres.

Image caption: In short, Auckland and (to a lesser extent) Hamilton have a reasonably even split between traffic lights and roundabouts, but the rest of our main centres have a clear leaning towards one or the other method of traffic management. Wellington, Christchurch and Dunedin are all about the traffic lights, while Tauranga is clearly a roundabout city.

• Auckland - The traffic behemoth  As New Zealand's largest city, it's no surprise that Auckland leads in the number of traffic light-controlled intersections AND roundabouts. Auckland's high traffic volumes and complex road network means traffic lights can provide more precise control over traffic flow, especially during peak hours, but interestingly there is still a very high number of roundabouts too.

• Wellington - Navigating the hills  The capital city's topography, with its many hills and winding roads, presents unique challenges for traffic management. Wellington's preference for signalised intersections, probably allows for more actively managed traffic flows in the city's compact central business district and along its main arterial routes.

• Christchurch – Rolling on the flat  In contrast, even with Christchurch’s relatively flat terrain, the city’s traffic is controlled by far more traffic lights than roundabouts.  Its grid-like street layout in many areas may contribute to traffic lights being a preferred option.

• Hamilton - Spinning around the ‘Tron  Hamilton’s flat spread probably means that either option is generally feasible, but in the end the city favours roundabouts to keep the traffic flowing.

• Tauranga - Embracing the roundabout  Tauranga is the roundabout capital of New Zealand. This huge preference for roundabouts could be attributed to the city's more spread-out urban area and lower peak traffic volumes (compared to larger centres like Auckland).

• Dunedin – Lighting up the south Like our capital city, Dunedin’s preference for traffic lights could be influenced by its hilly terrain and the need to manage traffic flow in its compact central area.

While it couldn’t really be considered a main centre, an honourable mention must also go to the mighty Palmerston North for achieving near 100% parity with a 44/47 split in favour (just) of roundabouts.

Now that we’ve established which cities favour which traffic management method, let’s dig a little deeper into why they may have made those decisions. 

The Great Debate: Traffic Lights vs. Roundabouts

Our urban planners and traffic engineers must often face the challenge of choosing between traffic lights and roundabouts to control or manage an intersection. Naturally, each option has its pros and cons, and the choice will often depend on specific local conditions.

Traffic Lights = Precision Control

Traffic lights offer precise control over traffic flow, which is particularly useful in high-volume intersections or where there's a need to prioritise certain traffic movements. For example, they can be synchronised to create "green waves" along major corridors as well as incorporate pedestrian crossing phases.

However, traffic lights can lead to increased delays during off-peak hours and require regular maintenance and electricity to operate. They also create a "stop/start" traffic pattern, which can increase fuel consumption and emissions, unless, of course, you are in an EV or a hybrid in which case stop/start driving adds to the regenerative breaking effect and increases engine efficiency. 

Roundabouts = Continuous Flow

Roundabouts, on the other hand, promote continuous traffic flow, reducing the need for complete stops. This can lead to reduced delays, especially during off-peak hours, and can improve safety by lowering vehicle speeds and reducing certain types of severe crashes.

The drawbacks of roundabouts include their space requirements, which can be challenging in dense urban environments (think Wellington). They can also be less effective at managing unbalanced traffic flows and may be more difficult for pedestrians and cyclists to navigate.

[A note: These pros and cons are high level and as previously mentioned don’t take into account local conditions. Any urban planners that can provide insight or commentary into the planning process for confirming traffic control options in their city would be welcomed.]

What does the future of traffic control look like?

As New Zealand's cities continue to grow and evolve, the balance between traffic lights and roundabouts may well shift. As cities become denser, space constraints might favour traffic lights over roundabouts in some areas. In time, Smart Traffic Management systems may enhance the effectiveness of traffic lights, allowing for real-time adjustments based on traffic conditions.

At NationalMap, we'll be there every step of the journey, providing the high-quality geospatial roading data needed to navigate these changes and pave the way for smoother, safer and more efficient transport operations.

If you believe your business can be helped by deploying NationalMap’s road network and routing data, then get in touch with us today.