I do it several different ways.
Sometimes I use a color photo of a real location and use a photo program to add my model like this one of the real Riverside Raceway and one of my models.

But with current tracks looking so much different than the vintage ones that my models would look at home on and very few color pictures from the '50's and '60's I've had to resort to building my own. I've built several "tracks" to use like this "dirt" track and some photoshop "speed blur" to add a little flavor.

Even if I love dirt track racing I had to do some pavement too. I use a lot of styrofoam in my bulding because it's light and, if you keep your eyes out for packing materials the most people throw away, it's mostly free.
Flat black paint makes excellent asphalt when applied to the aformentioned styrofoam sheets and corrugated cardboard makes great steel guard rails with a little silver paint.

Here's a grandstand the I built using styrofoam packing for the wall and cut styrofoam sheet to make the grandstand. Styrofoam looks a lot like concrete when you paint it with a light coat of flat white.

My favortie is my newest shop complete with secure storage area with chain link fence made from the metal from a real car aircleaner and privacy fence made from popsicle and corn dog sticks. The only commercial item in the whole scene is some 1/2" Midwest clapboard siding.
You'd be surprised where the next diorama piece will come from if you just keep your eyes open.