This indicator measures mass transit by calculating a ratio between trips and the resident population of the service area. Western regions like Portland and Seattle are included because their systems’ sizes are comparable to Pittsburgh’s. Their developmental histories differ from the majority of regions against which Pittsburgh is usually benchmarked. The chart below shows the number of unlinked passenger trips per capita for each benchmark region. Unlinked passenger trips is the number of passengers who board public transportation vehicles. Passengers are counted each time they board vehicles no matter how many vehicles they use to travel from their origin to their destination.