A few days ago I was building a cost surface (so maybe this belongs in the Spatial Analyst section).
The input was an extensive roads network, with different classes of roads (HIGHWAY", "MAJOR ROAD", etc).
I separated out each type, and rasterized the vectors, with an "impedance" value. This sort of equates to the speed of the road, or rather the times to pass through each pixel of the raster. So a highway would have less impedance than a street.
Then I had to combine these all back together to form my cost surface using con/isnull functions.
I was contemplating how to put together a multiple embedded con / isnull when I though I would give this a try.
