Roads and parking

I'm working on a roads and parking texture pack; I'm going for 15. But I need an idea of proportions. For instance when I render wall textures I do them at 5x5 for 5msqu wall, for fencing I render at 1.5x10, the texture is square, but rendered to stretch and not look stretched.
So what size prims are roads, parking lots, and sidewalks made from? Should roads be one lane, designed to be mirrored on the other lane; separate prims, or should the full width of the road be covered with one texture? And just what sort of road/parking lot/sidewalk textures are people looking for?

Just make your road or parking lot as natural looking as possible to your eye in your
external graphics program then select it edge to edge and crop it.

Then resize it to equal dimensions which of course will make it look like a square and
make it look somewhat squished.
However once you upload it into SL you can just resize it to the dimensions that it should be
on the prim.

This method works for most things as your basic prim size is 10x10 however if your doing
something that is very long and thin you could go 512x256 or even 1024x128, or any combination of similar values.

If it still does not look right once inworld, say you have diagonal lines in your parking lot
you can then use repeat and offset to correct it.