Calculating Accessibility Metrics 

Measuring access requires information on the potential trips that people might take. In brief, the following are required to calculate accessibility: 

• A set of geographic origins
• A set of geographic destinations
• A representation of the network with potential connections between origins and destinations
• A specific cost of travel, usually time 

For example, a health care accessibility metric might identify residences in an area as origins, specified clinics as destinations, and the roadway and pedestrian paths from each to each as the network. Then the cost of travel is measured by planning a trip for each residence origin to all reachable clinic destinations. Those data are summarized into metrics: how long does it take to reach the nearest clinic by driving? How long would it take via transit, or even walking? Calculating these accessibility values describes how well the land use and transportation systems are working together for residents.