Road Test: Traffic updates on your GPS - do they really work?

Daniel Long | 15 Dec 2008

There are any number of reasons why you could be delayed by traffic congestion and up until now, there’s been little motorists could do about it. We've road-tested a traffic-equipped GPS for a week to see if it can help.

There’s nothing more annoying that being stuck in peak hour traffic and not knowing exactly why you’re stuck there. Is it an accident? Roadworks? Oil spill?

Sure, you could listen to those generic radio traffic reports, with the sound of chopper blades whizzing in the background – but they’ve never been detailed enough to cover all the problem areas in big our cities, especially Sydney and Melbourne.

The magic component - Tomtom's traffic receiver plugs into your Tomtom GPS

That’s where the TMC (Traffic Management Controller) comes in: it usually comes as an attached accessory that measures about 2 inches – and is plugged into your GPS (if you have a compatible GPS), where it receives data from SUNA’s traffic management network. Keen to avoid those cable hassles? Mio's new top-end model, the Moov 370, incorporates an in-built receiver - but you'll still need to plug a seperate Antenna lead into it.

Garmin are halfway there: in addition to their traffic ready units, they provide an all-in-one cable that incorporates the receiver into the power cable and connects to the car cigarette lighter dock. We'll be happy when all GPS brands adopt a similar built-in method, eliminating cable mess once and for all.

Garmin's traffic module is an all-in-one job with the receiver and power cable bundled together

We tested the Traffic Management Controller (TMC) connected to the SUNA traffic network through some of Sydney’s busiest traffic areas for a week to see what the fuss is all about. Our results may surprise you.

How it works

Using the thousands of sensors already installed by road and traffic authorities across the major Australian cities (placed at intersections), this raw unprocessed data is transmitted back to the SUNA control centre, where it is then re-processed using SUNA’s own unique data algorithms.

It is then sent to your GPS, using a silently encoded FM signal that piggybacks on the 106.5FM band (don’t worry; you’ll still be able to listen to Richard Mercer’s love song dedications while using the service). That’s the simple version.

Mio's Moov 370 has the traffic receiver built-in - the best solution to avoid cable mess

Price

The TMC is ready to be used straight out of the box. As soon as the TMC is connected, it will search for a signal from SUNA (usually within seconds) and will actively display the traffic hotspots on your chosen route, if there are any. Thankfully, you don’t need a mobile phone and it doesn’t cost you a cent more; no added data charges are involved.

The only cost to you is the initial purchase of the receiver, which runs at about $150 as an extra accessory on most models or is bundled with the unit (be careful to check that it’s the right model if you choose the bundled option). Every SUNA compatible TMC ships with a lifetime subscription to the SUNA Traffic service.

(- Continued on next page - Real world testing)

Real world testing

We tested the TMC with the latest TomTom Go 930T. For a week, we braved the hectic, attack-dog frenzy of Sydney traffic to test the system. We chose the main peak hour commuting hours (morning and evening), when traffic is often at its worst, finger's crossed that the TMC would magically tell us where the traffic problems were, and advise us a sneaky exit strategy to avoid those areas.

The traffic service as it appears on a TomTom GPS (TomTom XL)

For this to all work, it depends on SUNA’s data being accurate, up-to-date and better than the helicopter reporter who watches down on us with glee. All great in theory, but as we discovered - this might be expecting too much.

There's still a fair bit of leeway to be expected as this technology. Even though it was launched in Melbourne 12 months ago, its still early days in the rollout. Sydney and Brisbane have only been online for the last few months and its only natural that users may experience testing difficulties as we did.

Hopefully, you get to avoid this by using a traffic-ready GPS

Trial by TMC - our driving test

Our main drive took us from Sydney’s upper northern beaches, through the narrow corridors of the lower North shore and into North Sydney, where our offices are located. In between our peak hour journeys, we also glided around the one way streets of the inner city, zoomed across the gridlock provided by the Harbour Bridge, took a few detours out West and generally went looking for traffic.

The notion of being told where the traffic is in advance seems like a sci-fi dream, but after a few rounds of using the device, it became a little frustrating.

In one case, we were warned at the start of our journey that there was a 28 minute delay to be expected on our trip - and the GPS offered us a choice to reroute our journey. To see how the TMC worked, we decided not to take the change of route, but to live dangerously and drive right on into the traffic snarl.

On the TomTom 930T (and all TomTom Traffic devices for that matter), traffic areas appear as a small driving icon to the right of the screen, on a vertical axis. The traffic icon is supposed to tell you how many kms you are from the traffic hotspot, except, the closer we got to the hotspot, the less the delay became until finally the delay had disappeared off screen entirely.

No traffic warnings at traffic hotspot?

Worse, once you are in the traffic hotspot - you're stuck. There are no travel warnings for the driver when you find yourself in a long bottleneck. Unfortunately, unless you were paying attention earlier while driving - you won't know how long the delay is or what type of delay it is, because the warnings came before; the traffic warnings are snapshot projections of a traffic site - they are not real-time traffic warnings inside the traffic area. It would be nice to be able to go back and read the warnings, but there is no review button or rewind to find prior warnings.

Rerouting

Surprisingly, during the many times we tested it, the TMC data warned us to reroute away from lengthy delays, even though the delays failed to materialise when we arrived shortly after. Although the traffic area may have looked busy, it was hardly the massive traffic snarl that we were led to fear. The data was simply showing a 'traffic snapshot'. Either way, it didn't match up to the real driving conditions.

In fact, only a few of the traffic bottlenecks that the TMC had warned us about were actually traffic problems in real life. What might have been a 28 minute delay only moments before, had suddenly morphed into a 2 minute nuisance – how could the data change so rapidly?

Another traffic example

In another case, the TMC warned us that traffic was supposed to be banked up for 3.8km in 3km distance awaiting us on our route (a 10 minute drive on the north shore). When we arrived, the extent of this delay was hardly longer than a couple hundred metres at best. If it had only happened once, we would of put it down to coincidence. But when it happened more than a few times, we grew skeptical.

Perhaps it’s a little unfair and unrealistic to expect the device to project accurate conditions at every moment. Traffic changes so quickly that by the time you get to the location, conditions may have changed.

Even so, these false positives dampened our expectations using the service. SUNA’s traffic predictions felt slightly unpredictable, though the anarchy of Sydney peak hour traffic made it feel like it was still worth having on board. Any warning is better than no warning, we decided.

Delays the system missed

Perhaps more troublingly, the delays that we did experience along our route near the surrounding suburbs of North Sydney were not being picked up by the service. This may have something to do with the faulty detectors on the road that we were driving on, or a little known traffic term known as data smoothing (see next page).

As we drove the same route everyday, familiar bottlenecks that spanned long distances refused to register on screen – one of the most frustrating features we found. On a couple of occasions we decided to reroute, only to push into more traffic.

Out of curiosity, we also tried taking our Tomtom GO 930T on the bus, but without power from the car battery (via the cigarette lighter), the TMC won’t work – which is a shame, because it would be nifty to get live traffic updates on your public transport route. Just think how popular you could become with the other passengers, knowing with annoying precision why the bus was taking an hour longer than usual.

(- continued on next page -)

How the system works - in more detail

Before we go into why the system didn't work for us, it helps to understand how it works in more detail.

We spoke with Brian Smith, General Manager of traffic and content at SUNA Traffic. As Brian explains: “We don’t broadcast the location. It comes from a pre-coded location table which sits in a digital map. That allows our very small bandwidth to be used highly efficiently. When the location code hits a number, the receiver finds it and that code equals a particular intersection. We broadcast 8 - 16 digit codes to be received by the GPS...All these codes and coding rules are controlled by that standard.”

At every traffic intersection, there are ‘loops’ installed to control the traffic lights. SUNA taps into this data, which is housed by the roads and traffic authorities in each state (maintained at 3 minute intervals, which is the normal time it takes for a traffic light loop to switch between red and green), and calculates the average speeds of those roads to see where the delays are. These loops are used to work out the ‘green wave’ – the traffic flow based on Australia’s unique SCATS protocol, which adjusts the green to red cycling time at the traffic lights. The system makes dynamical calculations to maximise this flow.

The Australian traffic system : what you should know

SCATS (Sydney Coordinated Adaptive Traffic System) is used in every Australian state, except QLD and has been sold to a number of overseas countries, including Dublin, Shanghai, Detroit and Hong Kong. That has allowed the SUNA traffic service to access the raw data that was already present.

Brian Smith elaborates for us: “Coincidentally it’s a central system, so all of that data comes back to a central processing point – we can analyse these loops in the road. We have our own algorithms – that system doesn’t calculate speed or delay. We use the unprocessed data from the traffic light system. We generate our own data from that.”

From this, SUNA generates congestion messages. The majority of congestion messages don’t have an incident message associated with them, but are automated and sent directly to SUNA’s computers, where they are processed further.

According to Brian Smith, the actual incidents “...are entered mostly manually by our operators. They come from a range of sources, (including) access to cameras, (specifically) traffic RTA cameras. We get feeds about scheduled road works from the RTA and we monitor a range of websites for events like the Sydney Marathon, Pope’s visit, etc. These specific road closures are pre-scheduled into the system. We also get data from the freeway loops that measure travel time etc."

SUNAs operators work behind the scenes to help with the automated data. There are two shifts – and each person is responsible for all of Sydney, Melbourne and Brisbane on their shift. The vast majority of data is automated, coming from flow data generated in the road loops and works on 24/7 basis.

SUNA ensures that operators are there to staff the full peak hour times and on Saturdays and Sundays. And for the times that the staff can't do it all, there's a computer system in place for that. “Any incident that results in congestion should be picked up by our automatic congestion system and broadcast the detection message”, says Brian Smith.

The TMC, in conjunction with the Nav software on your GPS may offer you the following choices when it receives traffic data: audible traffic warnings, traffic map display, type of incident, estimated delays and optional rerouting. SUNA are not just reliant on their computer systems and Roads Authority data; from time to time they send a 'Probe' team that uses quality control standards to check the accuracy of their data and how it correlates to real world traffic conditions.

Why didn’t the traffic data work for us?

We asked SUNA about the discrepancies in our tests and Brian Smith told us that it may come down to a few important reasons:

1) Data smoothing – “Traffic of the world is known worldwide as ‘noisy’. This data fluctuates quickly over time. It is designed for people (who are) one, two or three kms away and not for the people in it.

Smoothing requires a delay. If we get a signal showing congestion, then we hold it for a cycle. The traffic light cycle is approximately 3 minutes – which means we get new data approximately every 3 minutes – so if we hold it for another 3 minutes to see if it continues, and it can take up to 6 minutes for us to be convinced to begin processing (the signal).”

2) Narrow bandwidth - "Because it’s being broadcast on the FM network, the signal can only manage around 1 message/1 second. The time it takes for these messages to be transmitted can make a substantial impact to how we receive messages on the system.

We broadcast during peak hour 250 messages at one time – and it can take 3 to 5 minutes to run through the electronic carousel of all the messages. It can be 5 to 10 minutes of something happening in the street, before it’s received by the car”.

3) Subjective nature of traffic – “We can only broadcast a single message for a road, but there could be multiple problems for the road. We aggregate them together and make a call for the average person travelling down that road. It’s not about fine nuisances.”

4) Faulty detectors – “Occasionally detectors go faulty. That decreases our accuracy a bit. If one does go faulty, we look at the traffic either side and compute an (average) value for the one that was faulty.”

(- continued on next page - )

Looking ahead: future SUNA plans for Australia

Let’s be fair on SUNA – they’re using the most economical model they can. Because it’s based on the narrow bandwidth of the FM band, SUNA is hamstrung by the quantity (and size) of the messages they can send at any one moment. SUNA understand these difficulties, but they do have their cost benefits to the consumer and we should be thankful for that at least. A more expensive technology such as GPRS would probably require the service to require a monthly ongoing fee and Brian told us that customers are very wary of any ongoing costs - we couldn't agree more.

Fortunately, SUNA’s service is based a lifetime subscription model – so it’s worth considering that when you’re stuck in traffic next time. Brian Smith told us that they “...will absolutely increase bandwidth in the future.” He also told us about a future protocol based on TPEG that will use an 8khz band, although it’s probably quite a few years away from practical use he said.

SUNA hopes to expand into other Australian cities in the first half of 09, including Perth, Adelaide, and the ACT. Cities such as Darwin and Hobart could come online in late 09 or early 2010. Newcastle and Wollongong are currently on SUNA’s ‘wish list’, and it will come down to how economically they can balance those markets.

Traffic in-dash model, Ford Falcon

Overall Verdict:

The SUNA service feels like it still needs tweaking. The concept is great – a modern tech miracle to help conquer those stressful drives. But testing in real world conditions has convinced us that the TMC is still in its infancy. Too many times we were left wondering why the TMC had failed to see traffic bottlenecks coming. The reporting of delays needs to be more accurate; the way traffic bottlenecks are measured leaves much to be desired.

In time, as the technology gets cheaper, we’ll hopefully see the traffic warnings get better. If you’re thinking of purchasing a traffic-equipped GPS unit with the intention of becoming a more-informed driver, then it will do a great job at that. But if you think it’s going to solve all your traffic woes right now, you’re dreaming. The traffic helicopter reporter may have the last laugh yet.

** Postscript: ** SUNA have told us they will look into the trouble spots we found while using the service and send one of their GPS probes out to the sites that we experienced difficulties with.