Person occupancy estimates how many people are served by the vehicles they use on the network and can help to understand travel patterns and how many people are being served, as opposed to just knowing how many vehicles are being moved through a given corridor. Efforts to encourage carpooling behavior can also be evaluated using this metric.
| PERFORMANCE MEASURE | PERFORMANCE METRICS | PROJECT TASKS | APPROPRIATE CONTEXTS |
|---|---|---|---|
| Person Occupancy | Persons per vehicle (PMT/VMT) | Identify Needs Assess Alternative Strategies Refine Solutions | Urban Core Town/Urban Suburban* Rural* |
| *sometimes applicable, refer to metric description for more information | |||
- What? Evaluating the ratio of people per vehicle or the ratio of person miles traveled to vehicle miles traveled provides insight into how efficiently existing vehicle travel moves people. (Note that WSDOT measures person miles traveled that are reliable as one of its MAP-21 performance measures.)
- Why? Increasing the number of occupants per vehicle increases the network’s efficiency without additional investment.
- Where? This metric is most relevant for studying highway corridors where performance may be affected by changes in vehicle occupancy influenced by ridesharing or transit use. This measure could also be used where parallel transit facilities increase person throughput or reduce the growth in vehicle traffic on state facilities.
- How? For existing conditions, conduct vehicle occupancy counts or use WSDOT’s average vehicle occupancy tool to estimate the number of persons in each vehicle, which can be scaled to person throughput using a traffic count. For future conditions, use existing collected vehicle occupancy counts or output from the average vehicle occupancy tool and multiply against the vehicle volume outputs from a travel demand model or growth factor forecast to estimate person throughput based on vehicle occupancy.
| METRIC | SOURCES | DATA | ANALYSIS SOFTWARE | CALCULATION | RESOURCES |
|---|---|---|---|---|---|
| Persons per vehicle (PMT/VMT) | Household travel survey data Calibrated travel model Vehicle occupancy counts WSDOT vehicle and heavy truck count database Transit providers National Household Travel Survey US Census | PMT and VMT from travel surveys and/or travel models Average vehicle occupancy by trip purpose from household travel surveys and US Census Bureau Vehicle occupancy counts Transit ridership Traffic and Heavy Vehicle Counts | Spreadsheet software Travel demand model | PMT divided by VMT Persons divided by vehicles Average vehicle occupancy multiplied by vehicle volume | Regional travel demand models Vehicle and person counts Transit providers National Household Travel Survey US Census Bureau American Community Survey MPO/RTPO Household Surveys |