Hi Coyote, I'm in the middle of doing a city map commission as well - there has been a lot of pain and headbashing at my end (I'm trying to keep everything in vector). There are two ways to get an outline to your roads. First is to have an identical layer below the 'coloured' roads but this time the stroke in black with a slightly larger width. Second is to convert your road lines to a polyline (I'm using Serif Drawplus so I don't know what the equivalent is in illustrator) so the road becomes an editable shape. There is a third way in drawplus which is to add a stroke 'effect' to the line, but that rasterises the line so you're no longer working in vector.

If you want to know more just holler!
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Ravs