Dial 3-1-1 and ask for a traffic study. The Traffic Engineers will analyze the situation and decide what preventative device might be installed in your neighborhood and if the speeding situation meets the criteria for these devices. Tell them exactly where the speeding is the worst (give an intersection or address) and at what time(s) of day. The more information you can give them the better. The Police or Sheriff might also regularly assign motorcycle officers and radar units to enforce speeding laws in subdivisions as a direct result of citizen complaints.