Seeing red

By Geoff Cumming

Fed up with waiting at traffic lights that never seem to change? A frustrated Geoff Cumming goes in search of an explanation

Keeping an eye on the flow, the Joint Traffic Operations Control Centre at Smales Farm, Takapuna. Photo / Sarah Ivey
Keeping an eye on the flow, the Joint Traffic Operations Control Centre at Smales Farm, Takapuna. Photo / Sarah Ivey

I don't suffer from road rage; it's the lights that get me going. Or not going. I'm the agitated guy you see behind the wheel, venting pointlessly at the "stupid, stupid lights" that refuse to change long after the cars enjoying the green phase have scooted off.

I know I'm not the only Auckland motorist guilty of red light abuse. They're a favoured target of letter writers to the Herald and website postings. Right-turn arrows that let only three cars through when eight or nine are waiting inspire vitriol.

Green lights that beckon an approaching squadron of cars only to turn red drive us to distraction. Left-turning vehicles given only seconds after pedestrians have crossed are another flashpoint.

Delays from short-phasing traffic lights contribute to the congestion which, according to the most conservative study, costs our biggest city $250 million a year. More serious, especially for pedestrians, is the red light-running linked, at least in part, to drivers' impatience with lights that don't play fair.

Then there's the greenhouse gas emissions - just some of the issues drawing delegates from the Asia-Pacific region to a conference next week on "intelligent transportation systems".

They couldn't have chosen a blanker slate. Across this sprawling city of 1.4 million are more than 760 sets of traffic lights. In places they have sprouted like runner beans - the country's highest concentration is not in the CBD but in Clark St, New Lynn, where motorists must negotiate nine sets of lights in less than 1km. It's when you're running such gauntlets of apparently unco-ordinated signals that your passenger from Wellington or Bangkok inevitably pipes up about Auckland's third world infrastructure: "Why can't they phase the lights here like they do back home?"

Turns out, Auckland's system is the same as theirs - the Sydney Co-ordinated Adaptive Management System (Scats) adopted throughout Australasia. Contrary to perceptions, our signals act not in isolation but can be programmed as a network, with perhaps a dozen intersections in sync.

But Auckland is considerably bigger than Wellington and, compared to most other cities, its geography and lack of public transport complicate the task of free-flow. Where some cities' travel patterns are "tidal" - traffic moves largely in one direction in the morning and the opposite at night - Auckland's is like a ball of wool, with loadings often similar in several directions.

The more Zen among motorists might argue that we just need to calm down - that stop-go-stop is the lurching pulse of a city as car-reliant as Auckland; you'll get there eventually and the frustration wanes as soon as you get through the intersection.

But they're wrong. We are stuck with a traffic light system which, transport researchers suggest, is a camel. And, though fixing it is vital to keep the arteries from complete gridlock, improvements can be as incremental as a year of rush hours.

"The system was developed in 1970 and there haven't been huge changes to it since," says Dr Prakash Ranjitkar, a senior lecturer in transportation engineering at the University of Auckland.

The old local body structure's legacy of unco-ordinated lights, misaligned intersections and conflicting priorities is only now being fixed.

Traffic engineer Urie Bezuidenhout describes Auckland's version of Scats as "a quick and nasty system originally", with not enough sensors installed to measure traffic demand accurately. Scats relies on detector loops embedded in the road at intersections to count cars as they pass over and record the gap between them - data which gives some indication of congestion. Based on demand patterns, signal control boxes are programmed to follow a plan, with some ability to adapt to changing volumes.

"The signal controls make small adjustments based on information they collect - the more sensors, the better the information," he says.

"But the software can only do so much - you need operators to constantly tweak things."

One of Scats' limitations is that it cannot count the tailback, or number of cars in the queue. So if traffic piles up, it can take several phases before the system adjusts to clear the backlog - or alerts the operator that something is wrong. The system can go haywire, especially when motorists change their behaviour to "beat" the system - for instance, changing from a turning lane back into the main flow to avoid delay. "That's not what the system wants - it wants a constant pattern of behaviour," Bezuidenhout says.

The detector loops are also vulnerable to failure. When that happens, the system trips to default with phases set to off-peak.

Some experts maintain other signal control systems, such as the British-based "Scoot" system, are superior but Bezuidenhout says all have their limitations.

At the Joint Traffic Operations Control centre in Takapuna, they are watching and can see the bigger picture that the motorist battling the evening peak tide in Sandringham Rd cannot.

Monitoring the entire Scats network of 763 light-controlled intersections and 88 motorway on-ramp signals are just two staff - but the computerised network soon alerts them if signals are malfunctioning or intersections are jammed. If a huge tail develops, operators can override the programmed phasing with their own plan.

The JTOC centre combines the motorway network (controlled by state agency NZ Transport Authority) and the local road network (council-owned Auckland Transport) under a "single network" philosophy.

But keeping the motorways flowing takes priority, says Auckland Transport's traffic services manager, Ken Lee-Jones. The focus is broad enough to include the key arterials and ramps, which feed traffic on and off the motorways. Some of these intersections may handle upwards of 40,000 vehicles a day, demanding skilled interventions to keep them flowing. Though onramps and motorways have many detector loops to give more information, on most arterials they are restricted to the stopping line.

"Every vehicle passing over the detectors is a vote - the more votes it gets the more priority is given," one operator tells me (their bosses like to shield them from public identification).

Roadworks can throw the system out, requiring operators to rewrite the intersection plan. Utility companies also have a penchant for damaging the detector loops. "We do quick fixes. Then the engineers go in and do permanent fixes [to the control box]."

So when those right-turn arrows let only three cars through, it's most likely part of a cunning plan - to avoid overload at the next intersection, or too many cars joining the motorway queue six sets of lights away. Or the system may be prioritising what's supposed to be the busier route - which is what Auckland Transport is doing with its Route Optimisation project. But giving priority along one arterial implies delays for motorists moving across or against the flow.

Because of the limitations of the system, motorists do sit and wait unnecessarily, particularly in off-peak conditions or on weekends, when travel patterns grow even more complex.

Research can help. For his PhD, Bezuidenhout is developing an "add-on" to the Scats programme, which promises to better estimate queue lengths and adjust phase times accordingly. Despite the obvious commercial benefits of reduced delays, traffic engineers say they are hamstrung by lack of funding for research, while the council's budget for system improvements is tight.

So, it's not the lights that are stupid, it's lack of investment - and the Government-funded motorways get priority. In the future, apparently, we won't need traffic lights (at least, not in routine traffic). Drivers won't make split-second choices about whether to cross an intersection or wait, because cars linked by cellphone and Wi-Fi technology will "talk" to each other and decide for them.

Researchers, including Ranjitkar, are clearing a path for virtual traffic lights and a world of safe, seamless traffic flows and reduced greenhouse gas emissions.

With much of our vehicle fleet pre-dating vehicle-to-vehicle communications technology, that future might seem a long way off as we're waiting for the green. Some cities are not waiting for new technology and ripping out their lights (or at least turning them off at night) - with measurable savings in travel time and emissions.

In Auckland, the council is developing better information on congestion and alternative routes, with more electronic signage and website information for motorists to access on car "infotainment" screens. Next week's ITS Asia Pacific Forum at the Aotea Centre will showcase intelligent transport systems and their potential to beat gridlock and improve safety. The field trips are carefully timed to avoid peak hours.

For more information on the conference:

• To report faulty traffic lights, call *555 or the Auckland Transport call centre, 355 3553.

- NZ Herald

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