When you see a trap report it by pressing a button or by calling a toll free number. If you have a Smartphone like Nokia 95, Black berry it is easy for u. You can use your GPS to point the location and if you have basic handsets you will get an sms telling you where are the traps.
Trapster is basically an application not a website. It is basically a speed trap sharing system which also happen to be a website. Not only is Trapster free to use but also saves you from getting tickets. Register and let everyone know what only you know from your previous eperiences.
On a lighter note Cops are very smart , they change their Trap locations many times a day.