RF based vehicle tracking system.

Please share some of your ideas regarding my project as follows.

a). One RF recevier will be fixed in center location of an area.

b). Transmitter's will be fixed in truck's (appox. 100)

c). RF range is 2 km. when ever the truck passes in that range (when the recevier able to recevie the transmitted data), the data should be transmitted from the transmitter or other wise the data should be stored in the memory

d). When 100 of transmitter transmitts the same data the recevier should identify the data from which transmitter it has been transmitted.

My question is

a. what type of RF module is prefered to use.

b. If the truck is running at 100kph in that specified 2km range, can it transmitt the data.

c. if you having any special ideas or suggestion means please share with me

Thanks.