When employing an adaptive cruise-with-braking (ACB) system to control host vehicle following distance, a forward vehicle is detected using one or both of a radar sensor (14) and a camera sensor (82). The radar sensor classifies the forward vehicle as a motorcycle, passenger car, or heavy vehicle by comparing a detected radar signature to reference radar signatures for different vehicles. The camera sensor classifies the forward vehicle as a motorcycle, passenger car, or heavy vehicle by comparing a captured vehicle image to reference pixel and contrast profiles (PCPs) for different vehicles. An adaptive cruise control (ACC) module (12) selects and implements a following distance alert (FDA) protocol for the classified vehicle, where the FDA protocol prescribes following distance limits that inversely proportional to the size of the forward vehicle. Following distance limits can be further adjusted as a function of host vehicle mass.