Wasn't that in Bowdle, SD? Or was there another incident? I typically avoid dirt roads anyway, unless I'm well in front of the storm and know I can get back to pavement before the rain comes. My car will get stuck in an instant!Oh my gosh, having the radar and mapping on the same screen is priceless. As was mentioned, the shapefiles are detailed to the point of being ridiculous. You won't see the dirt roads until you zoom in, but you don't want them cluttering up a zoomed-out screen anyway. That would be entirely terrible. It is all user adjustable so that you only get the dirt roads at a zoom level of your choosing, though it is set by default with GRL3 at a reasonable setting. IIRC, the setting is located in the style file, where you can also choose what colors the roads appear. The interstate default color is white, for example, but I have changed mine to light blue, just as they usually appear on road atlases. The shapefiles often even show you where people's driveways are.
The caveat is that you cannot trust your life to the shapefiles being accurate. They are correct 99% of the time, but there was a notorious incident in NE some years ago when some chasers trusted them and they were wrong. The chasers found it necessary to drive across a corn field to escape a wedge and got stuck. Fortunately everyone survived, but the farmer called the sheriff and it got ugly.
The real beauty of it, the thing that makes it priceless, is that you can see your exact position relative to the storm right there on your screen. SN shows you where other chasers are, too.
Use the owners' forum for instructions, where you can ask questions. You'll have to create an account.
You can also ask me, to a limited extent.