Agree on this trap (it is one of the most prolific in western Fairfax county... a constant revenue generator). However, I disagree on the timing. The police in Fairfax County typically issue traffic tickets using two modes of operation so to speak. First you have some patrol officers who spend some of their time writing traffic tickets on occasion. Secondly, FFX county has a "motor squad," which are officers who focus exclusively on traffic enforcement. The "regular" patrols run speed traps mostly during slow daytime hours (typically 10am - 2pm), when the day shift does not have much to do (between rush hours), or late at night when again there is not much else to do.