NHTSA’s Crash Outcome Data Evaluation System (CODES) project linked crash, EMS, ED, inpatient hospital and rehabilitation, and insurance data for a twelve month period in seven states to generate medical and financial outcome information for everyone involved in motor vehicle crashes. The linkage was performed using a probabilistic linking algorithm. Occupantspecific population-based data for 879,679 passenger vehicle drivers and 10,353 motorcyclists were standardized for analyses that showed that safety belts and motorcycle helmets were effective in reducing mortality, morbidity, severity, and cost. The average hospital inpatient charge for unbelted drivers was five times the charge for those who were belted. Helmets were 67 percent effective in preventing brain injuries. Brain injured motorcycle riders had inpatient charges twice as high as those for the non-brain injured. Full results of this study are described in a Report to Congress (NHTSA, 1996) and its companion Technical Report (Johnson and Walker, 1996).