By most metrics, Lexus' "Intuitive Navigation" technology is thoroughly conventional. At its core is GPS technology augmented by the UK's radio-based RDS-TMC traffic information system. On paper, that makes it significantly less powerful and sophisticated than the best aftermarket navigation systems. It conspicuously lacks, for instance, the detailed traffic data provided by TomTom HD Traffic or any live services beyond the relatively rudimentary information delivered by RDS-TMC. Forget weather updates, Google Local Search or anything that requires an Internet connection. The 600h doesn't have one.
Likewise, it's not as effective as the best aftermarket systems when it comes to providing alternative routes based on either live or historical traffic data or estimates of delay durations. For the record, it's also worth noting that the system's postcode input is limited to five digits. It's not a major drawback, but again it does expose shortcomings compared to the best aftermarket systems. As for the Point of Interest (POI) database, well, much like those in other built-in sat-nav systems, it's hardly comprehensive and probably of marginal utility beyond locating service stations or a hotel in an emergency.
However, where Intuitive Navigation does score points is through sheer polish and ease of use. For starters, the 8in touchscreen is vivid and boasts excellent viewing angles. It's also extremely accurate. Rarely must you take a second stab at the screen when inputting commands or text. Just as good is the quality of the graphical interface it displays. Mapping data is rendered top-down and 2D with two colour schemes, optimised for day and night time use respectively. Superficially, that might sound old hat in the context of the latest 3D navigation systems. However, most 3D systems are frankly a bit of a ruse, more 2.5D than true 3D. In practice, Lexus' 2D maps are far slicker to look at than the likes of, say, the jagged pseudo-3D interface of a standard TomTom.
More importantly, they're clear and easy to follow. Thanks to the healthy 8in diagonal of the screen, the dual-map function combining large-scale and small-scale views simultaneously also works extremely well. The same can be said of the voice guidance notes. They're clear, well paced and give plenty of warning before junctions and exits. The system also deserves points for its speed and responsiveness. As a fully integrated system, it's always on in the background and therefore aware of the location of the car. During our week with the LS, it didn't put a foot wrong, never got confused about the car's location or sat there waiting to acquire satellite signals. Overall, it's an intuitive, stress-free and pleasant system to use.
There are, however, a few niggles. For starters, the voice command interface is extremely limited. Destinations must be pre-programmed into one of five memory slots, which can then be vocally requested by number. This is a particularly strange limitation given that the physically identical variant of the LS sold in the North American market supports full address input via speech recognition.
With that in mind, we also feel Lexus has gone overboard with the safety-related restrictions with which it has saddled the navigation system. The vast majority of options are locked out if the car is in motion. Only the five pre-programmed destinations can be accessed. Granted, it's clearly undesirable from a safety perspective to have drivers wrestling with complex information systems while on the move. But the downside is that front seat passengers are also locked out. In short, if you want to input a new destination or select one from the recent destination list using the touchscreen interface, even from the passenger seat, you must bring the vehicle to a complete halt.
On a final note, we are obliged to give the heads up regarding the navigation system's DVD-based underpinnings. That makes map updates more complex and expensive to perform because, typically, partial dash disassembly is required in order to swap the disk over. In short, it's distinctly undesirable compared to a hard drive based system.