The folks at speedtrap.org have updated their web site, making it easier to search your commuting route for speedtraps and potentially avoid a ticket.
Click on "find speed traps" and punch in your city and state. There are 18 listings for Arlington speedtraps alone.
Note of caution: Drivers aren't always sure what city they're passing through when they see a cop runnin' radar -- and the speedtrap listing operates on the honor system -- so the system is subject to error. But a quick check of several North Texas cities indicates the info is mostly reliable.