Method and apparatus for activating a crash countermeasure using a transponder having various modes of operation

A method for communicating between a first vehicle and a second vehicle comprising:

• generating a first vehicle data signal from the second vehicle in response to a cruise control signal using a communication signature;
• generating a second vehicle data signal from the first vehicle in response to the first vehicle data signal using the communication signature;
• determining a threat level in response to the first data signal and the second data signal;
• and
• continuing generating the first vehicle data signal and generating the second vehicle data signal when the threat level is above a threshold.

A method for operating a pre-crash sensing system for a first vehicle proximate a second vehicle comprising:

• generating a first vehicle data signal from a first transponder in response to an adaptive cruise control signal;
• sad first vehicle data signal including a first position signal corresponding to a position of the first vehicle and sensor signals from the first vehicle;
• receiving a second position signal from the second vehicle;
• determining a distance to the second vehicle in as a function of the second position signal;
• and
• determining a first vehicle trajectory from said first vehicle data signal, said sensor signals, and said position signal.