I found this info from other webboard. I will copy the message to show here below.
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The very nice feature you won't find in any 37xx other regions.
You can tell 3790CHN what exactly road you are driving on.
For example :: when you are driving on ordinary road and there are express way above & frontage road beside.
If 3790CHN is saying the wrong road that you are, you can correct it.
Just press on the green bar at bottom then you will see the choice of the other roads (as possible.)
From picture , if you are driving on express way not ordinary road so just press on express way name at left upper corner then nuvi will recalculate as you are driving on the express way. !!

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