Industrial parks are popular for criterium races ("crits") and practice races, which is probably what you're seeing there.

Here's one I've raced in a few times. Looks like it's not quite as popular, though! http://labs.strava.com/heatmap/#16/-89.48204/43.05660/yellow...

That's ucsb's crit & iv classic. Source: raced there many times. Info on crits http://en.m.wikipedia.org/wiki/Criterium