Due to the differences in length, height, and width between light-duty trucks (LDTs) and passenger cars, LDTs require more space on the road than passenger cars.  Because LDTs are taller and wider than cars, blind spots are created for cars following LDTs.  Cars following LDTs should allow a greater headway to maintain the same level of safety they would have when following a car.  Existing research on LDT-car following behavior conveys conflicting results on car driver following distance.  This study presents a model of LDT-car following behavior and, using data from a field operating test, estimates the corresponding passenger car equivalency of LDTs.  This equivalency is used to compute the cost of the blind spot externality.