That makes sense because many people are working two jobs now to make it in this economy. Maybe one job is during the day and the other begins at night. I don't usually go out during 4-6pm, so I don't know if its happening here. This is a more rural area so there is never much happening here. The traffic stays mainly on the highways.

Another thought I had is maybe you had an influx of illegals dumped in your area that aren't counted.