This report describes the status of freeway priority lanes in the United States, the development of a freeway priority-lane simulation model (FREQ6PL), and the application of the model to a real-life situation. Of the five feasible types of priority lanes, normal-flow exclusive lanes that reserve one or more lanes for priority vehicles are the most prevalent. FREQ6PL can simulate one or more lanes used exclusively by priority vehicles (buses only or vehicles of either three or more or two or more occupants). Three points in time are simulated: the before situation (no exclusive lane), the short-term after situation (the first day of operations with no traveler demand responses), and the longer-term after situation (3-6 months later, after spatial and modal shifts). Performance is measured by an integrated measure of effectiveness that includes costs of travel time, fuel consumption, and vehicle emissions and facility operating and maintenance costs. The model was applied to the Santa Monica Freeway in two parts:(a) to the priority cut-off limit, number of reserved lanes, and length of the exclusive lane and (b) to different parallel arterial speeds, different levels of arterial spare capacity, and different hypothetical mode shifts. It was concluded that reserving an existing or added freeway lane on such a freeway will at best make its performance as good as before and at worst significantly poorer in both the short-and longer-term situations./Author/