An analysis was performed to estimate the potential national costs and benefits of cooperative vehicle and roadway measures to enhance the effectiveness of driver assistance systems. These cooperative measures -- query-response communication systems, light-emitting-diode brake light messaging, radar cross-section paint-striping modifications, fluorescent paint for lane and other marking applications, passive amplifiers on license plates, spatial tetrahedral arrays of reflectors, and in-vehicle corner cubes -- are briefly described, along with assumptions that were made regarding performance. For the example lane departure case, the incremental nationwide effectiveness over an autonomous collision-avoidance system is estimated and monetized. This was generally determined with respect to annual crash-reduction savings, although the technique used allows other mobility benefits to be considered. The marginal benefits of providing each sensor-friendly technology were then calculated and aggregated across the various Intelligent Vehicle Initiative services so that a total marginal benefit was determined for each technology. Complementing this, a method has been established to estimate the magnitude of at- and near-intersection lead-vehicle-not-moving crashes for these technologies. Together, these methods illustrate national benefits across all crash types (the three-step process) and a more focused means to estimate benefits for a particular crash type (rear-end collisions at or near intersections), and provide a composite approach to the problem.