In-car navigation systems

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Hi there,

I'm doing a postgraduate course related to product design. At the moment I am studying in-car navigation systems - the ones fitted into dashboards or centre consoles rather than handhelds.

So far I've done lots of reading and I've seen product demos for some of the popular brands, but I'd like to have a better understanding of what drivers think about them, particularly if they use them regularly, whether for business or recreational reasons.

I'm not so much interested in the brand or technical engineering as I am about usability - the controls, the visual display, the audio prompts, how effective it is at helping you find your way, aspects that you really love or hate, things that you'd look out for next time you were buying a system.

By the way, you're not doing my homework for me just helping me make sure the system I design is easy to use.

Thanks in advance,
Mary S.