Measure vehicle speed using ultra sonic waves

Dear sir!
My name's Thanh Duong Le.I'm now a student of the university of Technology in Vietnam
Today, I write because I need your help to get some information about the machine to measure vehicle speed using ultra sonic waves.
Will you please help me some information:
-circuit scheme of this machine
-operation rules of this machine
-detail information about devices using in this machine
Please help me!!!
Thank you very much!!!!