When the "traffic" option arrived on GPS devices it seemed like the killer feature - immediate updates warning you of traffic jams, and intelligent routing that steers you around the worst spots.
In reality, it's not that simple. Some GPS devices, such as certain Navman models, receive updates about accidents and congestion via the SUNA service. But in TomTom's case, the traffic feature has been a snapshot of what traffic conditions are expected to look like, not what is actually happening.
That's now changed. Now TomTom has its own traffic service that attempts to warn you about what's actually happening on the roads as you're driving. It's called HD Traffic.
What's interesting about HD Traffic is that compatible TomTom units will now have SIM cards. The cards give each GPS unit a data connection, which is used to deliver updates on traffic conditions every two minutes. A TomTom representative tells us it's a 2G connection, and is set to constantly roam, so in theory, it shouldn't be hamstrung by the reception limitations of any one carrier. It also means you're online, so you can use the GPS to do a local Google search and check weather reports.
The new TomTom Go Live 820: the cheapest of the new models at $299
So how are TomTom units different to the other GPS brands when it comes to helping you avoid traffic?
TomTom claims one of the major advantages of HD Traffic is that coverage isn't limited to major cities. The traffic data actually comes from the cars themselves (as well as road sensors and other sources). Every car with HD Traffic acts like a sensor - building up a picture of traffic flow. The system also taps into alerts about traffic incidents.
This isn't a technique limited to TomTom GPS units. Other brands of GPS, using the SUNA traffic feature, tap into data that's been collected in a similar way from vehicles like couriers and taxis, as well as static road sensors.
As you'd expect, maps shown to us by TomTom paint a picture of much wider traffic data coverage outside major metropolitan areas than the SUNA network. But SUNA has been operating for several years now, and has had more time to fine tune their service in Australia.
The catch to all this? The HD Traffic feature is free for the first year, but after that you have to pay. This costs $69.95 a year.
You can also get HD Traffic on the iPhone, as a feature of the TomTom app for iPhone. This costs $7.49 a month, or $41.99 for a year and is an in-app purchase. You need version 1.8 of the TomTom app for iPhone, which TomTom says is a free update if you already own the app.
TomTom has released four new GPS models compatible with HD Traffic:
TomTom GO LIVE 820 (4.3in screen) - $299
TomTom GO LIVE 825 (5in screen) - $349
TomTom GO LIVE 2050 (5in fluid touch screen) - $399
TomTom GO LIVE 2050 World (5in fluid touch screen) - $499
Considering that you can pay up to $100 or so for map updates, the prospect of another yearly subscription is making GPS units start to look a little more expensive than they once were. Depending on your battles with traffic though, that might be a small price to pay.