Google Earth. Especially if you live in an area large enough to be covered by the high res imagery which is detailed enough to discern shoulder widths, lane markings, traffic signals, numbers of cars, etc.

See what maps and data your municipality or state DOT has made available. My city has released very comprehensive GIS data downloadable as ESRI shapefile or Google Earth KMZ's of just about everything I could possibly ever want to know about the roads in my area. I don't know how widespread this practice is but you might be surprised what you can find with a little looking around.